The Stovebolt Site Forums The Parking Lot Big Bolts what is the proper trans for a 46 2 ton

Hey All

I was wanting to buy a spare trans for my 46 2 ton, get it rebuilt and the swap it out over a weekend.

But I realized I don't know if there are differences between the 4 speed used in the 1.5 ton or 1 ton, nor what year trans is appropriate.

Can anybody share some light on what exact trans I should be sourcing?

thanks in advance

Jay,

I think only the 2 ton has a parking brake on the tail of the transmission while all of the other open driveshaft models are much the same.

Paul

Jay,
This should answer your question.
46 Truck Specs
Harold

according to that page, the specifications for all 4 speeds is exactly the same for 1946. This is a chevrolet, not a GMC, if that matters.

Does anybody know the years that were the same? 41-46 etc.

Hy Jay_Brown, I think that trans. was used from 1937 to 1947, a non synchronized four speed, hope that helps.

I wish you were closer. I have the 4 speed I pulled out of my 46 2 ton in the TBD pile.

Jay,
Look at the top of the page I posted. This is for Chevy.
Harold

As far as I know , there was only one 4 spd for the 41-46 trucks, for both Chevy & GMC, 1/2 ton on up.
Known as the sliding gear 4spd, meaning straight cut gears with no sinchros.

My 45 GMC 400 series 2 1/2 ton came with the same.

Some had the drum style parking brake bolted to them, while some of the bigger trucks had a lever bolted to it with rods & cables to the rear wheels.

As far as I know the GM SM420 was used in all Chevy and GMC trucks from 1/2 ton up to 2 1/2 ton. There was an option for Chevy and GMC 1 1/2 to 2 1/2 ton for a Clark 5 speed. Three ton and up had 5 speed either the V or VO models (V) being direct drive and the (VO) being Overdrive models. i.e 205V or 205VO and 207V or 207VO.

My 1950, 2 ton has a SM420 with e-brake cables to rear axle as does my 1948 1 ton, while my 3 ton has Clark 5 speed with drive-line drum e-brake.

Before 1947 1/2 GM used the non-synchronized 4 speed SM420, as a new feature in mid 1947 (about May)the SM420 added the synchronized 4 speed, but still called an SM420.

If you want to stay specific to you year model go with per 1947, if you want a smother shift then go with the post 1947 1/2 (1948 - 1962) model. they bolt the same and take the same clutch. Only difference is internal to the gear box.

Also, there are a lot of parts and kits around for the later model synchro style.

Oops...back then Chevy did not build anything larger then a 2 ton. Or so I have been lead to believe.

Good Luck...happy motoring.

I'm pretty sure that Chevy changed the bolt pattern to the bell housing in 1948. Before that, the pattern was smaller, so 1948 and later transmissions won't fit a 1947 and earlier Chevy.

Maybe things are different for GMC.

I cannot find any document that says that the 1947 and earlier GM 4-speed was named SM420? I cannot find anything about that transmission (manufacturer and model number), except in the Shop Manual. Does anyone have a link to information/name of that earlier standard non-synchromesh transmission?

I don't think the non-synchromesh 4-speed had a particular name, but it is a totally different case with little to nothing in common with the SM420.

I have a 46 2-ton and it has a non synchromesh GKT 134 in it. This was a transmission made by Chevy, not Muncie like the SM420. When I was doing research on it I was able to find a gasket kit... That was about it. Once I pulled it apart I was able to take the bearings up to our local bearing store and they were able to order in new bearings.

Thats all the info I had found!

Thanks, Randy

It looks like the GKT-134 was available at least from 1931-1947.

I cannot find any information on who made it, or what GKT refers to?