1958 GMC 336 tranny match up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

59chevy310p · 05-14-2017, 02:53 PM

Long story short got a 1958 GMC with the factory Pontiac 336 and I'm gonna be converting it to 4x4 trying to figure what tranny will bolt up to it so I can run four wheel drive. Didn't know if a turbo 350 will bolt right up. Anyone have some advice?

dwcsr · 05-14-2017, 09:21 PM

Quote:

Originally Posted by 59chevy310p

Long story short got a 1958 GMC with the factory Pontiac 336 and I'm gonna be converting it to 4x4 trying to figure what tranny will bolt up to it so I can run four wheel drive. Didn't know if a turbo 350 will bolt right up. Anyone have some advice?

Different pattern you would need something like this

http://www.wilcap.com/pontiac.html

Port&PolishMan · 05-14-2017, 09:59 PM

This Site does the Trans Swaps & Many Transmission Adapter Plates ..

You have to Dig around , but it's all there ..

https://www.novak-adapt.com/catalog/...er-case-parts/

1project2many · 05-14-2017, 10:08 PM

The Wilcap parts look complete and reliable. The flywheel spacer is an important part of installing an adapter. Couldn't find anything on the Novak page.

Port&PolishMan · 05-14-2017, 10:39 PM

[QUOTE=1project2many;7942793]The Wilcap parts look complete and reliable. The flywheel spacer is an important part of installing an adapter. Couldn't find anything on the Novak page.[/QUOTE

Depends on what Transfer Vase Your going to use ..
That have lots of Adapter Plates for that . .

https://www.novak-adapt.com/catalog/...o-transmission

Do You have the SM465 ?

After Cruising that Site - Their Engineering does look Better . . !

59chevy310p · 05-15-2017, 12:16 AM

I have the stock 4 speed manual tranny in it right now. currently don't have any tranny or transfercase for the project just getting started and trying to figure out what I can use.

1project2many · 05-15-2017, 09:00 AM

If you're OK with keeping a 4 speed the M420 is a tough transmission. The original NAPCO conversion was an add-on kit and used a divorced transfer case. Divorced transfer cases were common on trucks in the '60s and '70s and one advantage to using this style case is that you don't have to change any of the original engine or transmission configuration.

A later SM465 may bolt to the original bell housing. It does in the Chevrolets but I'm not going to promise it will work in the GMC with the Poncho engine. If you can use an SM465 then you can use a later transmission/transfer case assembly.

Many later 4X4 trucks have a wider stance which comes with with wider axles and wider spring mounts. Finding axles that fit under a TF with no modification can be a challenge. IIRC the 72-ish Dodge 1/2 ton trucks are very close. They also happen to use a divorced transfer case, the NP205, which is very tough. International and Ford trucks from the early '70s also used a divorced case but the axles may require more work to install.

05-14-2017, 02:53 PM	#1
59chevy310p Registered User Join Date: Oct 2015 Location: Monroe, wa Posts: 43	1958 GMC 336 tranny match up Long story short got a 1958 GMC with the factory Pontiac 336 and I'm gonna be converting it to 4x4 trying to figure what tranny will bolt up to it so I can run four wheel drive. Didn't know if a turbo 350 will bolt right up. Anyone have some advice?

05-14-2017, 09:59 PM	#3
Port&PolishMan Registered User Join Date: Mar 2017 Location: Etowah, TN Posts: 210	Re: 1958 GMC 336 tranny match up This Site does the Trans Swaps & Many Transmission Adapter Plates .. You have to Dig around , but it's all there .. https://www.novak-adapt.com/catalog/...er-case-parts/

05-14-2017, 10:08 PM	#4
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,200	Re: 1958 GMC 336 tranny match up The Wilcap parts look complete and reliable. The flywheel spacer is an important part of installing an adapter. Couldn't find anything on the Novak page.

05-14-2017, 10:39 PM	#5
Port&PolishMan Registered User Join Date: Mar 2017 Location: Etowah, TN Posts: 210	Re: 1958 GMC 336 tranny match up [QUOTE=1project2many;7942793]The Wilcap parts look complete and reliable. The flywheel spacer is an important part of installing an adapter. Couldn't find anything on the Novak page.[/QUOTE Depends on what Transfer Vase Your going to use .. That have lots of Adapter Plates for that . . https://www.novak-adapt.com/catalog/...o-transmission Do You have the SM465 ? *After Cruising that Site - Their Engineering does look Better . . !* Last edited by Port&PolishMan; 05-14-2017 at 10:59 PM.

05-15-2017, 12:16 AM	#6
59chevy310p Registered User Join Date: Oct 2015 Location: Monroe, wa Posts: 43	Re: 1958 GMC 336 tranny match up I have the stock 4 speed manual tranny in it right now. currently don't have any tranny or transfercase for the project just getting started and trying to figure out what I can use.

05-15-2017, 09:00 AM	#7
1project2many Registered User Join Date: Mar 2012 Location: Lakes Region NH Posts: 3,200	Re: 1958 GMC 336 tranny match up If you're OK with keeping a 4 speed the M420 is a tough transmission. The original NAPCO conversion was an add-on kit and used a divorced transfer case. Divorced transfer cases were common on trucks in the '60s and '70s and one advantage to using this style case is that you don't have to change any of the original engine or transmission configuration. A later SM465 may bolt to the original bell housing. It does in the Chevrolets but I'm not going to promise it will work in the GMC with the Poncho engine. If you can use an SM465 then you can use a later transmission/transfer case assembly. Many later 4X4 trucks have a wider stance which comes with with wider axles and wider spring mounts. Finding axles that fit under a TF with no modification can be a challenge. IIRC the 72-ish Dodge 1/2 ton trucks are very close. They also happen to use a divorced transfer case, the NP205, which is very tough. International and Ford trucks from the early '70s also used a divorced case but the axles may require more work to install.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.