3 on the tree

[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]

Originally Posted by melmashman

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/produ...s-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]

Originally Posted by melmashman

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]

Originally Posted by raycow

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