The Stovebolt Site Forums The Shop Area Engine Shop 1946 GMC vs. Chevy Differential

Hello;

I own a 1947 GMC half ton, long bed. (it's the 46 body style, manufactured in early 47)

I here conflicting stories, I was hoping someone here might have the experience and knowledge to help me out a little.

Some tell me that the drive train, differential are the same for chevy and gmc. others tell me they are different. Does anyone know for sure?

The reason I am asking, is I would like to change the differential gears to boost my speed a little for highway driving.

I would prefer to use the original differential, and put new gears it, but I am not opposed to putting in a new rear end.

Anyone with any information regarding either option, I would be very greatful.

I know very little about these trucks, I only know about mine, as I tinker with it, I don't know how it relates to other vehicles from gm, trucks or cars.

Thanks guys,

Brian

Brian, For a definitive answer, I would call Patrick Dykes of Patrick's Antique Cars and Trucks. He sells the gear sets so I am sure he would know of any differences between Chevy and GMC....520 836 1117

The diffs are the same but most GMC's use a different trans and the torque tube is there fore not

Do you want to go to an open driveline?
Do you have a 'compound low 1st and a reverse lockout leaver on the trans?

Thanks guys, 53 4 me, thanks for the contact, I shall give him a call.

J.H.Proffit , to answer your questions,
Do you want to go to an open driveline?

I would prefer to stay with the torque tube, but my goal is to re-gear so I can run at highway speeds comfortably. I would like to stay original as possible, but open driveline would be acceptable if i get the desired results.

Do you have a 'compound low 1st and a reverse lockout leaver on the trans?

I will be honest, your second question confuses me??? I think the answer is no to each part, but I'm guessing these are available on heavier trucks??? mine is a 1/2 ton with simple 3 speed transmission.

If you go to an open drive line, are there any modifications required to the end of the trans? seals? etc?

thanks again guys!

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Remember drugs are keepin' me alive!!NOT ADVIL

Brian, as far as I know you should have the same tranny and rear-end as any other '46 Chev./GMC, but with a short driveshaft extension between the back of the tranny and front of the torque tube to make up for the longer wheelbase. Do you have an extension there, about a foot long? You are sure about being a 1/2-ton (6-lug wheels)? In those years GMC made 1/2-tons with both a short and long wheelbase, Chev. only made short 1/2-tons. I would guess Patrick's 3.55 gears would fit your rear. If you want to be sure, pull the gears out and bring them up here, I've got a set of Patrick's gears on the shelf we can compare them to.

Hey there Barry!

I believe it's a half ton, cuz that's what I was told.

There aren't any tags anywhere to tell me model number.

Here's a couple of pics, one shows the rear axle, the other shows the front part of the torque tube/extension.

The truck does have 6 stud rims, what does that make it?

Sorry, photos are large, may take a while to load.

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Barry, I may take you up on your offer, but it won't be at least until early summer most likely. Thanks for the offer, I'm going to mark it down so I don't forget.

I've got a couple of parts books coming, hopefully they will give me part numbers so I can compare part numbers to the chevy.

Thanks again to all who have helped! I look forward to more feedback.

Brian