3 on the tree

[tinman64]

I've got a 64 1000 with a three speed column shift,the trans seemed to up shift OK but down shifting was impossible,the only way to down shift was to come to a complete stop then it would free up.The other day I decided to try to adjust the shift linkage under the hood,again it up shifted not too bad but this time it went into 3rd and now it won't release.I have disconnected the shift rods,tried moving the arms at the trans,nothing moves,I don't want to break anything but the thought has crossed my mind,any words of wisdom out there or shall I just look for a bigger hammer.Any help would be appreciated.thanks. Dave

[raycow]

Save the hammer for something you don't like.

This is highly unusual, but you may have jammed the interlock inside the side cover. You can drain the transmiision oil and unbolt the cover to take a look.

If the interlock is free (that is, you can move the shift arms with the cover off the transmision) try shifting the 2-3 shift sleeve into neutral. Just use a screwdriver between the sleeve and the input shaft gear. If the sleeve won't move, you have something binding inside the transmission and it will probably have to come off the bellhousing for further disassembly and inspection.

Ray

[tinman64]

Thanks for the info Ray,I'll give it a try,I'm still on the fence on the OD tranny,I hate the idea of cutting a hole in the floor for the shifter,if this 3 speed doesn't work out it may be just the push I need to go to the 4 speed.

[raycow]

I'm still on the fence on the OD tranny,I hate the idea of cutting a hole in the floor for the shifter.

I don't like cutting a hole in the floor either. Just to clear up any possible confusion, if you go with the SM318 w/ Borg Warner overdrive you can keep the column shift. The 4 speed A-833 and 5 speed T-5 will both require a hole in the floor.

Ray

[melmashman]

Hi Ray,

I seemed to have lost the link to the Overdrive resource. I think it would be a great addition to my 1965 305e truck/camper.

Any advice you can provide in obtaining & installing one would be appreciated.

Thanks,
Mel Mashman

[raycow]

I seemed to have lost the link to the Overdrive resource. I think it would be a great addition to my 1965 305e truck/camper.

Any advice you can provide in obtaining & installing one would be appreciated.


Hi Mel -

I think this is the link you are asking about.
http://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=925247

If that guy's offering is already sold, you could try looking on ebay and craigslist. Other possibilities would be some of the Chevy car and truck forums. They often have a "for sale" and "wanted to buy" section. You could start with Chevytalk, but I know there are others too.

Installation is very straightforward if you have a SM318 in your truck now. The O/D transmission will fit your existing bellhousing and clutch. The worst you would have to do is replace the yoke or shorten the driveshaft. You will also need a manual control cable for the lockout lever. An ordinary choke or throttle cable of suitable length will work, but the real O/D cables are a little heavier than that. Any truck or tractor supply outlet should be able to fix you up with a cable

I will be happy to help you with the wiring when you get to that point, but the electrical hookup is actually pretty simple.

Ray

[melmashman]

Hi Ray and Others,
I am actually getting closer to doing something to the transmission on my 1965 GMC Truck/Camper with a V6 305e and three on the column. My understanding is that it is a 3/4 ton truck with a 1 ton rear end.

I found a shop that specializes is transmission changes for older trucks in Tucson. Here is my need: I plan on doing some cross country trips and even returning to Alaska from Arizona. I also will be taking many short trips in Arizona. Of course there will be some mountain driving, but I can do that at low speed. I am not looking for great gains in mpg, just the ability to not be a traffic hazard on interstates.
Currently it is geared to go up ANY mountain, but seems like it is going to explode at 55mph. It would also be nice to have a synchronized 1st gear.

I think a 4 or 5 speed transmission would be a wonderful way to enhance the engine's life if I plan on going 65mph max. I am willing to cut a hole in the floor. I am also willing to change the rear end gear ratio. I know that a simple overdrive would be a solution, but I wonder if the 4 or 5 speed would be a better match for my long term needs.

I would like to be reassured that a 4 or 5 speed is really designed to handle the load of a camper. I don't really need an automatic. I plan on avoiding city driving.

Remembering that I have a pretty heavy camper on it, is a 4 or 5 speed recommended? The transmission would be rebuilt and a new clutch would be inserted (the old one has over 100K on it). I would prefer the 5 speed if it makes sense. Does it make sense? Also, what specific transmission should I be seeking.

Thanks for any advice you can provide. I value it!
Mel

[raycow]

Addition of the camper changes things somewhat.

The SM318 and T5 are rated for only about 6000 GVW and might not hold up satisfactorily in the long run with the camper. The A833/MY6 overdrive 4 speed is quite a bit stronger and would be a good choice if you don't need a 1st gear much deeper than you have now with the SM318. If you need a grannny 1st gear, you would want something like an NV4500. This is a truck 5 speed with a granny 1st and an overdrive 5th.

The A833 is a relatively easy install. If you get the right one (next paragraph) it will bolt directly to your stock bellhousing after you open up the center hole to 5.125". This is a simple job that any machine shop can do. It is the same length as a "long" SM318 (about 21" from the bellhousing face to the rear seal) and has a 27 spline output. If you have a long SM318 now, the most you will have to do is change the yoke. With a "short" SM318 (about 16"), you will need to shorten your driveshaft.

The one gotcha is that the GM version of the A833 was made with two different bolt patterns and only one of them will work with your bellhousing. You definitely need to take a look at what you are buying before you lay down your money. The one you want has a normal GM bolt pattern that looks like the one on your SM318. The transmission you DON'T want looks like the one on the left side of this pic:
http://i98.photobucket.com/albums/l266/rebeldryver/NP440b.jpg
The transmission on the right has a normal GM pattern, but that one is a Muncie, not an A833.

If you want to use an NV 4500 there is no version which will bolt directly to your bellhousing. Fortunately, Advance Adapters sells a plate that will let you use a Dodge NV4500, but not the GM version.
http://www.advanceadapters.com/products/712550--dodge-nv4500-5-speed-transmission-to-a-gm-v8-adapter-plate-kit/
You will still have to open up the center hole the same as for the A833 and also modify the driveshaft.

Ray

[melmashman]

Thanks Ray for the informative response. I have a lot to ponder.
The truck will only be used as a camper so your insight into the load limitations of other options was spot on. Thank You!
I think the NV 4500 would be great since it supplies a granny gear as well as an overdrive, but I need to check the difference in the costs since the A833 would more than likely solve my problems. I was looking at a site that had the NV 4500 and it was going for nearly $4k by itself. I was thinking that the whole job could be done for that, but perhaps I am not being realistic.
Do you know of suppliers for the A833 and the NV 4500 that might be more reasonable?
Thanks AGAIN,
Mel

[raycow]

I was looking at a site that had the NV 4500 and it was going for nearly $4k by itself. I was thinking that the whole job could be done for that, but perhaps I am not being realistic.
Do you know of suppliers for the A833 and the NV 4500 that might be more reasonable?

For $4K I would hope that NV4500 is a new one.

Seriously, I was thinking a trans for a swap like that would come from ebay, craigslist, or a salvage yard. I mean, that's where I usually look for mine. However, I can certainly understand your wanting some kind of warranty with it.

I did a quick check for rebuilt units and found the following:
http://www.drivetrain.com/parts_catalog/manual_transmission/manual_rwd_transmissions.html
http://www.heavytruckparts.net/search.php?qsearch=TRUE&ManufMake=GM&Model=MY6&PartID=4000

Drivetrain.com is a well-known supplier that has been around for a while. The WM Cohen outfit I have never heard of before. It might be worthwhile to do a more extensive search (for price) before you commit to a supplier.

The main advantage of buying "used" rather than rebuilt is that you usually don't have to pay a core charge and you can get additional parts which don't normally come with a rebuilt. Thiis is especially important with the MY6, because you definitely need the correct shifter, mounting plate, and linkage rods for it. That particular shifter was not used on any other transmission and was never offered to the aftermarket. The shifter (or its parts) are no longer available from GM. Hurst doesn't sell parts for it either, although I understand that Hurst may offer a rebuilding sevice (not sure how they do that).

A salvage yard unit will usually carry an "out-the-door" warranty. That means it is guaranteed to be good as purchased, but not for any extended length of time after that. It is best to ask how much time you have to install and test it. On ebay or craiglslist, any warranty would be up to the individual seller.

If you want to try for a rebuilt MY6, ask if the seller can supply the shifter, even if you have to pay extra for it. This is less important on the NV4500, as the shift mechanism is located in the top cover and those will usually interchange between different models. The NV4500 stick can be swapped if you need a particular shape to clear your seat or dash.

Just as a reminder, if you want the NV4500, it has to be for a Dodge truck application in order to accommodate the thickness of the adapter plate. The input shaft on the GM version is too short to use with an adapter. Also, the Dodge unit has to be for a gas engine, not diesel (you want a 1-1/8" input spline).

On the A833, you want the GM version (often called MY6) and it must have the regular GM bolt pattern. Ask to see a picture of the front face if there is any doubt. Either trans needs to be for 2WD (not 4WD) or you will have to find some potentially expensive parts to adapt it.

Ray

[melmashman]

Hi Ray and Others,
I thought I posted this, but perhaps did not submit it.
I just drove in over 100 degree mid day heat about 233 miles mainly downhill and flat from Prescott to Tucson. My wife followed me in a car with flashers on since I was going 50-55 on a 75mph stretch of I-10.
The V6 with 3 on the tree never overheated and provided a great ride, but an overdrive would have made a huge difference in driving safety at 65mph. I did not see a single one-finger hand jester so I would call it a very successful trip.

On Monday I am taking this to a Hot Rod shop which does custom transmission work. I have passed on your great e-mails on the MY6 and Dodge NV 4500 conversion. I am leaning towards getting the NV 4500 because a Granny Gear and an Overdrive seem like a good match for my heavy camper configuration.

I am not sure on the rear-end gears. I'll have them count teeth and ask you what you think about keeping it as is or modifying the rear end. My understanding is that it is a 1 ton rear end on a 3/4 ton truck, but that is all I know.

Let me know if you think I'm crazy doing this transmission conversion:-) I assume others have done it and I would really like hearing their pros and cons. I know putting a hole in the floor is against some purists concepts, but I plan on taking this vehicle on many long excursions rather than having it just for show. As it is, many heads turn when they see the vehicle which is in wonderful well-cared for shape.

Thanks again for ALL your suggestions and feedback. I clearly would have gone down the wrong path without your help.

Cheers,
Mel

[raycow]

Let me know if you think I'm crazy doing this transmission conversion:-) I assume others have done it and I would really like hearing their pros and cons. I know putting a hole in the floor is against some purists concepts, but I plan on taking this vehicle on many long excursions rather than having it just for show.

Not crazy in the least. IMO, most older trucks are geared much too low for comfortable highway driving. I installed a T-5 in mine over 10 years ago, and I still think it is the single best improvement I could have done on it. My truck does get used as a truck, but doesn't have to carry a camper, so the T-5 has been trouble-free all this time.

Ray

[melmashman]

Hi Ray and Others,
The shop that I am using that does many transmissions is unable to get an adapter for the Dodge NV4500. They spoke with the adapter folks and it does not fit and would require a lot of tweaking. They were reluctant to do something that they would not guarantee working and I commend them for that.
I have not purchased the NV4500 so I'm not out any money, but wondered if the 4 speed with perhaps a change in the rear end will be much better than just putting an overdrive on.
Anyway, I have plenty of time, but I am a little frustrated with the process.
They mentioned the possibility of putting in an automatic, but I really would rather have a stick than deal with that adaptation which could lead to further issues with transmission overheating with my heavy camper.
Anyway, I'll investigate further to verify they really have the Dodge and not the GM version of the 4500 and I will have them see about getting the 833 4-speed which I understand is an easier install.
My question is there anyone that has actually made these conversion that I might be able to have the shop talk to.
Let me know,
Thanks,
Mel

[raycow]

Mel, as I see it, you are in kind of a difficult situation here. You don't plan to do the work yourself, and I can fully understand the reluctance of your shop to do a job that they don't feel good about warranting. At first I was going to suggest that you look for a shop which is more focused on rod-type projects, but then I re-read your earlier post and saw that you have one of those now.

For that reason, I am confused about some of the other statements in your post:
"The shop that I am using that does many transmissions is unable to get an adapter for the Dodge NV4500. They spoke with the adapter folks and it does not fit and would require a lot of tweaking."

Does this mean that Advance can not supply the adapter which I suggested (P/N 712550), or does it mean that Advance has the part, but does not believe it will work for your application? If the latter, why do they say it won't work?

In my earlier post, maybe I wasn't clear enough about the swap not being a bolt-in. Perhaps I should have posted the link to the Advance instruction sheet at that time, but I didn't, so here it is now:
http://www.advanceadapters.com/downloads/712550.pdf

I have done this swap (on a Chevy, not a GMC), and the adapter absolutely does fit as described, but some machine shop work is required. First, on any bellhousing 1967 or older, the center hole has to be opened up to accept the 5.125" register diameter on the adapter. Second, I didn't want to use the suggested Ford release bearing because I was concerned about a potential interface issue between the bearing and the stock fork. Instead, I machined the Dodge release bearing support to fit a stock GM bearing (about 1.375"). Lastly, I had to modify the driveshaft, but I think you expected that anyway.

Naturally, all of this is dependent on using the correct transmission. It has to be for a Dodge, not GM, and it has to be for a gas engine, not diesel. All of this is very easy to verify if you can measure the input shaft. It has to stick out about 7-1/2" from the transmission face, and it must have a 1-1/8" spline diameter (same as a stock GM clutch).

I see that Advance now sells the correct Dodge input shaft:
http://www.advanceadapters.com/products/52-0219--dodge-nv4500-gas-input-shaft/

However, I don't know is this is to allow the use of a GM transmission with their adapter, or if it is sold only for replacement purposes in a Dodge transmission. You will need to ask Advance about this. If it does work in a GM transmission, this will make the swap somewhat easier.

As an alternative to the NV4500, you are correct that the MY6 (A-833) is an easier install. It is certainly less expensive than an NV4500 and will save you the cost of the adapter. You also save quite a bit of weight. However, it still isn't a bolt-in. You will need to machine the bellhousing the same as for the NV4500. Also, the case was made with two different bolt patterns and only one of them will work. Lastly, the correct shifter can be a real PITA to find if one doesn't come with the transmission.

The conventional 4-speed (like an SM420) with a taller rear axle would be a distant 3rd choice. First, the good news: The SM420 is is almost a bolt-in swap. It will bolt to your bellhousing with no modifications at all because it was a factory option. This also means that you could very well find the correct driveshaft for it at your friendly local salvage yard. All you may need to do is cut the hole in the floor.

Now the downside: You may not be able to get tall enough gears for your rear end. At this point we don't even know what kind of rear you have, so you will need to identify it first before you can go looking for gears. If no luck on the gears you will have to swap in a rear from a later year truck. It has to be approximately the same width as the rear you have now, because narrowing a rear can get expensive. Fortunately, Ford and Dodge also used the same 8 bolt wheel pattern, so you should have a fairly good selection to choose from besides GM. Keep in mind that just about any rear end swap will require relocating the spring pads and also driveshaft modification. You will also have to cobble the parking brake hookup unless you get an SM420 that has an integral parking brake. Lastly, the 3-4 gap on the SM420 is quite a bit wider than on the MY6 (or 4-5 on the NV4500). This means you may not have an entirely suitable gear for climbing hills at highway speeds when fully loaded.

Ray

[Rick]

Hello,

I was having trouble with my 3 speed linkage. I went to the manual, it has an excellent section describing how to adjust the shift linkage. Last 5 years mine has shifted flawlessly.

[melmashman]

Hi Ray,
Thanks for the informative response. I have a lot to ponder indeed.
I did note that at the bottom of the page related to the Advance Adapter Download PDF it mentioned a "Heavy Duty Dodge NV4500". I was wondering if there is another NV4500 Heavy Duty different from the "normal" Dodge NV4500. Were they just providing an adjective or is there really a separate Dodge gas NV4500 that is Heavy Duty?
Again thanks for sticking with me. I am passing your comments onto the very savy person at HotRods of Vale in Tucson. Perhaps they have been looking at the wrong NV4500. It is certainly worth asking. Actually they are corresponding with the NV4500 folks as the adapter folks and seem to be pretty thorough, but it's worth asking.
Cheers,
Mel

[raycow]

I did note that at the bottom of the page related to the Advance Adapter Download PDF it mentioned a "Heavy Duty Dodge NV4500". I was wondering if there is another NV4500 Heavy Duty different from the "normal" Dodge NV4500. Were they just providing an adjective or is there really a separate Dodge gas NV4500 that is Heavy Duty?


Mel, I saw that note too, and I agree that it could cause some confusion. There definitely is a "heavy duty" version of the NV4500, and this is the one that was used behind the diesel and V-10 gas engines. The fastest way to identify it externally is the 1-1/4" input shaft. Even though Advance suggests that it can be used by swapping the bearing retainer, I think you will have trouble finding a clutch disc for it that would work on a GMC. The "standard" NV4500 has a 1-1/8" input shaft and that one will fit the stock GMC clutch disc.

Ray

[steve c]

Mel, I saw that note too, and I agree that it could cause some confusion. There definitely is a "heavy duty" version of the NV4500, and this is the one that was used behind the diesel and V-10 gas engines. The fastest way to identify it externally is the 1-1/4" input shaft. Even though Advance suggests that it can be used by swapping the bearing retainer, I think you will have trouble finding a clutch disc for it that would work on a GMC. The "standard" NV4500 has a 1-1/8" input shaft and that one will fit the stock GMC clutch disc.

Ray

Ray the transmission is not the issue the GMC V6 bell housing is the problem, the depth required to use the adapter is incorrect. The Chevy and GMC bells have completely different dimensions also the GMC has the pilot bearing in the flywheel not the crank. The application for the 712550 is for GM V8 not V6 the depth required from the face of the bell to the pilot bearing is 6-5/8" the V6 only has 5-11/16 making the shaft on the NV4500 too long. We can change the input and bearing support to a GM one but then its too short requiring milling the adapter about .187 thinner plus modifying the mounting holes as the V6 trans has 2 bolts going from the inside out and 2 going from the outside in plus counter boring the adapter to fit the front bearing support. This is all in theory of coarse since we don't know anyone who has done it including Advance Adapters. I hope this clears up any confusing about this application.
Steve

[raycow]

Steve, thank you for taking the time to clearly explain the problem with the adapter. I think I now have a better idea of what you are up against.

The bellhousing depth issue you mentioned still has me puzzled though, and here is why: A friend of mine with a 63 GMC V-6 pickup blew his stock 3 speed SM318 transmission and asked me to help him get his truck running again in the quickest and least expensive way. We ended up installing a Chevy passenger car transmission and it went all the way into the bellhousing without the input shaft bottoming out on the pilot bearing. The bottom two mounting holes were unthreaded just as you described, and I had to use longer bolts with nuts in those two holes. The only part we had to swap from the GMC transmission was the side cover because the shift arms were different.

The reason it took this long for me to answer your post is that I had to catch up with my friend first just to see if his recollection of the swap agreed with mine. This happened a long time ago, and my memory isn't what it used to be.

I hope you can come up with a transmission or rear axle swap that will work on Mel's truck to get his engine revs down at highway speed.

Good luck with it.

Ray

[steve c]

Thanks for the info Ray about the Chevy trans swap now you have me thinking again about this. I think I need to speak to Advance Adapters again and try to explain the dimensions again because all the seem to be concerned with is the bell housing depth not the actual depth from the pilot to the face of bell. The Chevy bell is 6-5/8" while the GMC V6 bell is over 8" that's why I gave them the other dimensions but they didn't take into account that the crank protrudes into the bell housing on the Chevy,knowing that dimension may be the answer . I will still have to modify the mounting holes for the trans to the adapter and bore out the bell housing but that's easy. I believe once I can get the correct dimension for the Chevy ( not the bell housing depth) it will end up being the same as what I measure on the GMC if its not and it wont work I will talk to Mel about another option which would be an SM465 with a Gear Venders overdrive. Thanks for all the help
Steve

[raycow]

Hi Steve -

Thank you for the update.

I am glad to hear that you haven't given up on this project and are still looking for a workable solution. Mel is very fortunate to have found you.

Ray

[melmashman]

Ray and Others,
I received the note below from Steve who I have complete confidence, but wanted to get a 2nd opinion. The NV4500 solution just is not going to work due to adapter issues.
Steve is recommending an SM365 4 speed with a change to the rear end to provide lower RPM's at highway speeds for about $3k. The splitter option he mentioned is too expensive. Based on your expertise would you recommend this SM365 approach? Hey - thanks for your help!!
Thansk - here is Steve's message:
Mel,
The easiest and most cost effective solution is to just put in a new clutch and reinstall the 3 speed but its not going to help with the highway driving, I think a good option is to put in the SM465 and change the rear end gear to something more suited for highway speeds. The overdrive unit I was looking at is the best option but also the most expensive (around $3300 just for the unit plus the SM465), its a completely different unit from a regular overdrive built into a transmission its an add on that would go on the back of the SM465 and it allows you to "split" each gear if you wanted in other words you have a overdrive in each gear except 1st so technically you would have a 7 speed transmission this is all controlled by a button on the shifter you have the option of turning it on or off in each gear. I'm not sure you really need something like this or want to spend that type of money. I'm guessing we can put together the SM465/gear change and all necessary components for around $25-$2800??. We have a 1968 GMC (shop truck project) with a 305 V6 and the SM465 trans/ bell housing as long as the transmission doesn't need major hard parts like an input shaft or gear set we can rebuild it and put it in your truck if the trans is not re-buildable we would need to buy one from Novak or another source this would bump the cost up depending on the price of the trans. I'm waiting for our transmission builder to come back from vacation to discuss this option. Let me know if you think this is something your interested in.
Thanks

[Rick]

Mel,

I converted my 62 sm318 to a "old style" 3 speed + overdrive (from a chevy).
I paid $400 for the unit, and another $350 to have it checked out, repaired and resealed.
This was 7 years ago, the unit has worked flawlessly since. (once I got the bugs worked out)
It is almost a drop in swap, only the rear yoke, needs to be changed.
I have it in a 62 1000 series. With the original 305 & 3.07 rear gears, I get as high as 18 mpg on the freeway (65 mph engine runs 1750 rpm)
Today I have it behind a 401 in the same truck and get the same mileage.

I feel this is the most practical swap you can do. Yes, other transmissions are better, faster shifting, stronger & smoother. But cost wise you cant beat this swap.
Note here: this transmission has handled the torque of my 401 for more than 5 years. However I do not abuse it.

My 2 cents,
Rick Rusconi

[raycow]

Mel -

IMO, Steve's solution is workable, but it all depends on a major unknown: Finding a suitable rear end.

First, you need to determine your present ratio, so you know what you are starting with. This is easy enough to do by counting driveshaft revolutions. There is no need to take the cover off and count the teeth unless you want to. Next, you need to decide how much rpm reduction you want, as a %. Most overdrive transmissions run in the 25-30% range (0.70-0.75 O/D ratio), just to give you an idea of what is out there.

You probably have a H052 or H072 rear (3/4 and 1 ton, respectively). These two are very similar, with the main difference being wheel bearings. The tallest gear ever offered for these was 4.11, so I don't think you will be happy with another of the same type. GMC also used a Dana 60 rear for some 3/4 ton applications, and taller gears are available for this one at least down to 3.54.

In 1973, GM replaced the H052/72 with 2 versions of the 14 bolt rear, which may still be in use. I don't know the specific ratio applications, but they are definitely available in the 3.xx range. This is something you will have to research. The main problem with the 14 bolt is that all the ones I have measured are wider than the rear you have now. Assuming you want to keep the wheels in the same place, you will either have to get wheels with a different offset, or else narrow the axle housing (expen$ive).

Fortunately, other truck makes used the same 8 bolt wheel pattern that you have, so you can extend your search to include Ford and Dodge in the hope of finding one of suitable width.

Regardless of what rear you end up with (including later GM), it isn't likely to be a bolt-in, mainly because of spring pad spacing, so you will probably have to relocate the spring pads. You will also have to cobble the parking brake cable hookup unless you get a transmission with the parking brake on its output shaft. Fortunately, those are fairly common.

As for the SM465 transmission, it will almost bolt up, but not quite. You will have bore out the center hole in the bellhousing to accept the SM465 bearing retainer. The "correct" 4 speed for your truck would be a SM420, which will fit your bellhousing without needing any modification. The SM465 wasn't offered until 1968. Both transmissions are of similar strength, but the SM465 has better parts availability, particularly the 2nd gear synchronizer, which is getting hard to find for the SM420.

Rick's post got me thinking again about the SM318 and its GVW rating. It didn't seem reasonable that GM would sell a truck with a transmission which wasn't adequate for the maximum GVW of the truck it was installed in. I wasn't able to find the applicable GMC literature online, but I did look at some Chevy specs. The C-20, which is their 3/4 ton, is rated up to 7500 GVW, and it came with a SM318. Their next heavier series, the C-30, is rated up to 10,000 GVW and you couldn't get a SM318 in that one. If you wanted a 3 speed, you got a T-89, which is stronger.

So where I am going with this is that I was wrong about the 6000 GVW rating for the SM318. If you are at 7500 or less, GM claims it is strong enough for the job. This means that the SM318 with the B-W O/D should again be given consideration. It will definitely be an easier and less expensive installation than the SM465 plus a rear end swap. Btw, the B-W O/D can also be used as a gear splitter if you wire it for manual control, which is what I did in all the cars I installed one in. As I said in a previous post, I would have one in my truck now if it had come with a column shift.

Ray

[steve c]

Thanks for the info on the rear end Ray I have not looked into which axle Mel has or looked for a ring and pinion. The trans swap will be easy since we have the correct bell housing no machining will be needed , the shop truck we have has all the correct parts. The SM318 sounds like a good option but I have yet to find one. The Gear Venders OD with the SM465 would be very nice but just very expensive.
Steve

[raycow]

These things do turn up on ebay, but they go pretty fast. You just gotta grab them before they get away.

http://www.ebay.com/itm/Manual-3-speed-overdrive-transmission-1958-1959-1964-Chevrolet-rat-hot-rod-GC-/150897744620?pt=Vintage_Car_Truck_Parts_Accessorie s&fits=Make%3AChevrolet&hash=item232234daec&vxp=mtr

http://www.ebay.com/itm/1958-1959-1960-60-1961-1962-Chevy-Impala-Bel-Air-3-speed-overdrive-transmission-/370833576611?pt=Vintage_Car_Truck_Parts_Accessorie s&hash=item56576752a3&vxp=mtr

Ray

[David R Leifheit]

And sometimes these transmissions "fall" into your lap.

Okay, it *looks* similar but it is out of a Ford (was bolted to an inline 6 I scrapped out of a mid 60s truck).

Somewhere I even have the "overdrive" cable to control it. :)

*If* I ever get to work on my '62 1000 this will probably be the transmission, or I'll see if the overdrive will bolt onto a GM transmission. I think the difference is the mounting from the case to the bell, and probably the splines.

http://www.oeltd.net/doc/parts/IMG_0780.JPG
http://www.oeltd.net/doc/parts/IMG_0781.JPG
http://www.oeltd.net/doc/parts/IMG_0782.JPG
*note* big pictures...

[raycow]

*If* I ever get to work on my '62 1000 this will probably be the transmission, or I'll see if the overdrive will bolt onto a GM transmission. I think the difference is the mounting from the case to the bell, and probably the splines.

That's a pretty good transmission you have there. It's a T-85 or T-89. You can tell which one if you take off the side cover. T-89 has straight cut L&R gears. T-85 is helical.

BOP bellhousings were made with the Ford bolt pattern in the 60s, but never Chevy or GMC. You MIGHT be able to bolt that trans to a GMC bellhousing with an adaptor plate, but I'm not sure if the input shaft is long enough to allow for the plate thickness. Longer input shafts were made for AMC, Stude and Willys/Jeep applications, and those will usually swap. but they won't be easy to find. GM input shafts are about the same length as Ford.

The O/D unit and midplate might bolt onto a GM case if you drill a hole for the reverse lockout rod. GM pattern T-85/T-89 cases are pretty scarce though.

If it were mine, I would get it apart now just to just to halt any further rust progression. That thing is too valuable to lose.

Ray

[tatastruck]

Sorry to hijack. I have a 64 long bed with three on the tree and they have already relocated it to the floor however I really don't like this transmission so I'm looking to change it to the 4 speed. How hard is that will it bolt up to my existing bell housing?

[raycow]

I'm looking to change it to the 4 speed. How hard is that will it bolt up to my existing bell housing?
If you get an SM420 transmission (used 67 and earlier) it will bolt to your present bellhousing with no modifications needed. You will need to replace the driveshaft, and, of course, cut a hole for the shift tower.

If you get an SM465 (used 68-up), you will also need to have the bellhousing center hole bored out to approximately 5.125" to accept the front bearing retainer. This is a job any machine shop should be able to do.

Ray

[tatastruck]

[QUOTE=raycow;49507]If you get an SM420 transmission (used 67 and earlier) it will bolt to your present bellhousing with no modifications needed. You will need to replace the driveshaft, and, of course, cut a hole for the shift tower.

If you get an SM465 (used 68-up), you will also need to have the bellhousing center hole bored out to approximately 5.125" to accept the front bearing retainer. This is a job any machine shop should be able to do.

Ray

Do I need a new clutch or tailshaft? Are the splines the same?

[raycow]

Do I need a new clutch or tailshaft? Are the splines the same?

You won't need to do anything to your stock clutch. The input shaft length, splines, and pilot are the same as on the 3 speed.

Not sure what you mean by tailshaft. If you are talking about the transmission output shaft, you won't need to do anything to that. It should have a flange or yoke on it that the front U-joint bolts to. You WILL need to replace the driveshaft, though. The 3 speed and 4 speed driveshafts are entirely different.

Ray

[David R Leifheit]

Addition of the camper changes things somewhat.

If you have a long SM318 now, the most you will have to do is change the yoke. With a "short" SM318 (about 16"), you will need to shorten your driveshaft.

Ray

Since the transmission is -shorter- wouldn't he have to lengthen the driveshaft?

[David R Leifheit]

The O/D unit and midplate might bolt onto a GM case if you drill a hole for the reverse lockout rod. GM pattern T-85/T-89 cases are pretty scarce though.

If it were mine, I would get it apart now just to just to halt any further rust progression. That thing is too valuable to lose.

Ray

Valuable?

Would you cringe if I told you it spent at least a year, maybe two, just sitting out in the yard... coupled to the motor... but in the weeds. I only brought it into the cover after I gave the motor to a scrapper.

I refused to part with the transmission.

[David R Leifheit]

Sorry to hijack. I have a 64 long bed with three on the tree and they have already relocated it to the floor however I really don't like this transmission so I'm looking to change it to the 4 speed. How hard is that will it bolt up to my existing bell housing?

Since it has already been relocated to the floor, I *assume* a hole has been cut for that. You might try scrounging the wrecking yards to see if there is an unmolested 4 speed floor cover (ie. one with a factory hole in it).

I know that on my first truck, the butcher job done to move the three-speed to the floor would have remained a nasty hole if I hadn't replaced the cover.

[raycow]

Since the transmission is -shorter- wouldn't he have to lengthen the driveshaft?
I could have written that better. What I meant to say was that if he had a short SM318 on the truck now, he would have to shorten his present driveshaft in order to use it with the O/D transmission, because all of the overdrives are long.

Ray

[raycow]

Valuable?

Would you cringe if I told you it spent at least a year, maybe two, just sitting out in the yard...

I have already cringed. As soon as I saw your pics, I KNEW it had been sitting out in the weather.

When I said valuable, I meant scarce. You might have to look for a long time before you find another T-85/T-89 with overdrive. If you do intend to use it, you might want to start looking now for a GM pattern case. That won't be easy to find either.

Ray

[raycow]

Hey guys, one of those overdrives on ebay is gone already, and I can hear the clock ticking on the other one. Going, going.......

http://www.ebay.com/itm/Manual-3-speed-overdrive-transmission-1958-1959-1964-Chevrolet-rat-hot-rod-GC-/150897744620?pt=Vintage_Car_Truck_Parts_Accessorie s&fits=Make%3AChevrolet&hash=item232234daec&vxp=mtr

Ray

[tatastruck]

If you get an SM420 transmission (used 67 and earlier) it will bolt to your present bellhousing with no modifications needed. You will need to replace the driveshaft, and, of course, cut a hole for the shift tower.

If you get an SM465 (used 68-up), you will also need to have the bellhousing center hole bored out to approximately 5.125" to accept the front bearing retainer. This is a job any machine shop should be able to do.

Ray

If I happen to find NSM 420 in a junkyard how would I identify it?

[raycow]

If I happen to find NSM 420 in a junkyard how would I identify it?

You might want to print some of the pics on this page and take them with you.
http://www.6066gmcguy.org/SM420.htm

Lacking the pics, a quick and dirty way to tell the SM465 and SM420 apart is that the 465 has two PTO covers and the 420 has only one, on the left side. The 420 also has a very significant "bulge" on the right side of the case.

Ray

[raycow]

Mel or Steve -

Please take a look at this truck.
http://6066gmcclub.com/forum/showthread.php?t=47666

It has 8 hole wheels and definitely a Dana rear. You might want to look at your truck to see if you have one of those in there now. If you do, then all you might need would be a gear swap. If not, then this could be the rear you might want to look for, because it would be the right width.

Ray

[BarryGMC]

The floor on a 66 is different than the earlier trucks. its like the 67-72. the auto and 3 speed rigs have a solid floor. the 4x4 and 4 speed trucks have a bolted in high hump. You have to cut out the floor and some of the firewall and graft in the corresponding high hump parts. Also any 420 trans from 47-67 will work. however there are 4 yoke sizes used 1310-1330-1350-1430. There are 2 case styles that were made. The best ones are the 65-67 with the extra ribs cast in the case. Finally nearly all 47-67 gm trucks with a 4 speed have the 420 trans. There is the odd new process 435 in the 60's.

[David R Leifheit]

The floor on a 66 is different than the earlier trucks. its like the 67-72. the auto and 3 speed rigs have a solid floor. the 4x4 and 4 speed trucks have a bolted in high hump. You have to cut out the floor and some of the firewall and graft in the corresponding high hump parts

Not necessarily. I have had 3 '66 GMCs and only the 1000 had the one piece floor. The 1500s have had a removable hump.

[raycow]

Also any 420 trans from 47-67 will work. however there are 4 yoke sizes used 1310-1330-1350-1430.
You have to watch out on the 54 & earlier transmissions. Some of them were made for a torque tube. You can identify these by the ball seat machined into the bearing retainer.

Ray