Rear end swap

[randallgrunert]

Currently I have a 4-10 rear end in my 65 1500. Resently I install a Holley 500 and that made a world of difference. But I am still taching really high at 65mph. How much difference will I see if I swap to a 3-73. Would really like to put in a T5 but they are hard to find. I have a chance to get a Muncie 4 speed and coupled together think I might have a good combination.

[raycow]

Going from a 4.10 to 3.73 would reduce your engine rpm by 9% at any given road speed - not worth the cost and work, IMO. What you really need with those gears is an OD transmission, like the T-5. I am surprised to hear you couldn't find one - they practically grow on trees, and they cost a lot less than a Muncie would cost.

I put a T-5 in my truck because I couldn't find an A-833 - now THERE is a scarce transmission. Anyway, the T-5 is the best thing that ever happened to the truck. It has been in there for about 10 years now, without a moment's trouble. I had a SM420 and 3.90 gears before I put in the T-5, and I still have the 3.90. What transmission do you have now?

Ray

[tommyduncan]

As far as I know none of the Muncies have an overdrive so that wouldn't help your problem.
The T-5 does have an overdrive and would help a lot as long as you use your truck like a car. If you tow or carry heavy loads it won't last long.
Your best bet would be a gear swap.

[randallgrunert]

Right now I have the 318 3 speed coupled with the 4-10. If I install a T5 should I also do a rearend swap? What T5 should I look for. I have found several mustang. Can I use my old bell housing and will the T5 bolt right up. I know i'll need to change out my clutch disc to a 26 spline I believe and then have my driveshaft reworked. I'm just tired of pushing the engine so hard. I won't be pulling a trailer, basically it will be a driver and maybe some local car shows. Thanks for any imput. also if any one in central Calif. has info on a T5 I would greatly appreciate it.

[raycow]

Originally Posted by randallgrunert

If I install a T5 should I also do a rearend swap? What T5 should I look for. I have found several mustang. Can I use my old bell housing and will the T5 bolt right up. I know i'll need to change out my clutch disc to a 26 spline I believe and then have my driveshaft reworked.

Don't bother with the Mustang T-5s - they won't bolt to your bellhousing. The only T-5s with the right bolt pattern are Camaro/Firebird and S-10 92 and earlier. Only the S-10 has a shifter location which will clear a stock bench seat. To clear the seat with a Camaro box you have to put an S-10 tail housing on it. S-10 and V-6 Camaro T-5s take a 14 spline clutch disc. V-8 Camaros are 26 spline.

I recommend leaving the rear end alone until you get enough driving time on the T-5 to decide if it needs changing.

If you need more info, feel free to ask.

Ray

[BarryGMC]

Put 3.54 gears in the rear. This is the best for a 3/4 ton truck. I have done this so many times its hard to remember them all. The t 5 is not a strong tranny and will die if you use a truck as a truck. Nobody used this car trans in any real truck and there is a reason... Honor your tough gmc truck heritage and keep it tough.

[randallgrunert]

I found a T5 tranny out of an 85 camero, and now I'm trying to get my clutch kit. At NAPA they have a clutch kit for my truck 10 spline. I know I need a clutch disc with 26 spline. If I order the clutch for my truck and order a clutch disc with 26 spline the disc are different diameters. old is 12 inch and the Camero is 10.4". Will this work or does anyone have part #'s that will get me going. Thanks for any help.

[raycow]

It's no problem to use a disc that is smaller than the pressure plate. The problem is that you may run into trouble on the hub protrusion. The GMC disc is one of a kind, and Chevy discs don't normally work for replacement. You might have to machine the hub shorter or have a rebuilder make a custom disc for you. This will all make a lot more sense when you compare the two discs side by side.

Ray

[BarryGMC]

My experience is that there is no difference with the clutches. 10 to 12. I have done a few hundred. All of the mis info is sad. 420 and465 trans clutches are so common it's unbelievable. On my bench are a 12 from a gmc v6 a 12 from a 292 one ton 69 and a mix of 10 to 11 truck clutches from 59 to85. I can mix most of the parts from all of these and make a good clutch. The reason the v6 part number is no good is that gm v6 request are so rare that they have dropped it. A 420 or 465 and the clutch are the same for gmc and Chevy.

[randallgrunert]

So Let me see if I have this right When I install my camero T5 tranny I need a 26 Spline clutch disk I don't need to do any other modifications to the clutch? I have a clutch shop right down the road a few miles and they didn't think I needed to do any thing else. They will build me anything I need Clutch disk, diaphragm type pressure plate and throwout bearing for around $180. Off the top of your head what is the spline count on the output shaft of a 318? The Camero is 27 I know. Thanks for the help. I will be submitting photos of the transmission shifter mod as things progress.