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It seems a lot of people change the rear axle on their trucks. From what I understand this is because it’s a torque tube, not a U joint axle. I have a 52 3600 truck with a U joint axle. Is this the factory rear end and is there any reason I couldn’t or shouldn’t use it? I would like to change the gear ratio but would keep the drum brakes.

Hello Neighbor,

In 1952, only the 3100 used the torque tube rear axle. The 3600 uses the Eaton HO52 axle, which was used from 1946 until sometime in the 70s. 4.10 gears are available used, but are hard to find.

It's the factory rear end. That era 3/4 & 1 ton has a partial torque tube from the trans to a cross member and a flange that connected to an open drive line type rear end. There is an optional rear end available which is from a 67-72 truck with an auto trans. It has a 4:10 ratio. They are getting difficult to find however. There are numerous posts about this subject on this site.
Fred

the 3600 is a different animal when it comes to the brakes and rear end also has a longer box and running boards.
some parts are the same.
most who want a taller geared differential end up going to the junk yard with a tape measure and finding something that will fit
then you have to weld new spring perches and shock mounts

do your research before you start doing stuff with a 3600 some parts are available some aren't

evaluate what you have and then decide what to do based on the condition and what parts you need

If I can't change the rear end gears, can I make it up in the transmission. I'm thinking of lower gears ratios in the transmission, like 2.85,1.85,1.31.1.0,.77. My goal is to be able to drive my truck at least 75-80 mph, with some acceleration. I want to keep up with traffic.

The OD tranny is the way to go but I think you are expecting too much speed out of a 216. My 248 tops out around 75 on flat ground with no wind. I'd recommend a disc brake upgrade with the higher speeds.

Concur with Cletis. I did the 4:10 3rd member upgrade to my 3800 (I have a 235 engine). Top speed I have been able to attain is 72 (going downhill) and 69 on level ground. It runs out of horsepower before it runs out of gears. It will cruise comfortably at 65 MPH now. BUT ... Cletis is also right about the brakes. I keep doubly aware of what's going on at that speed and hope like crazy I do not need to panic brake.

Also, next up is a front axle rebuild (king pins, ball ends, etc). 72 MPH is a little tense

Going to taller gears in either the rear axle or the transmission will tax your 216 or 235 considerably. You will not have a lot of acceleration.

John

Matt, if I were in your shoes, I would go with a T-5 transmission with the .70~ overdrive gear, and keep the stock rear end gears. The T-5 with the extra shifts will keep the engine in its optimum power band more often than a factory 4 speed which you start in 2nd gear (1st is granny gear for pulling stumps).
The stock rear end gears, even with the .70~ overdrive, will keep you from going faster than the stock brakes can stop you, while allowing you to keep up with highway traffic (excluding Mr Milliman, of course).
Carl

I put myself in a position to find out top end on 59 gmc,235 3 on the tree,390 or 410 gears with 7:00 16 tires.it did about 80 mph,but coming off a hill i heard a loud pop and motor wasnt running well.that move coused me to find a piston without a hole in it and instal.maybe was askin for to much,hmmm

Wots50, not meaning to get off topic, but did you change the rear in your truck. I know the GMC came with a 270 and 3.07 gearing from factory. My 58 was one of those and the 235 just wasn't up to the task with that rear gear, a small block resides there now. It'll cruise 65/70 once you get it moving, 1st is a little tall in my opinion.

Matt, the 235 is a great engine, if that's what you have in your truck, but with a few exceptions just isn't up to those speeds regularly. They were designed for 50's era roads and just not up to todays speeds. I'd pull it and update the drive line with the speeds you're wanting putting the original drive line aside in case the next owner wants to put it back. That's just my thoughts and it's your truck. Larry

Sorry, I should have said this in my earlier post. I am changing the engine to a 1964 small block 327.

Ok the challenge with a rear end swap is finding one that is narrow enough to fit.
nothing is going to be a simple direct bolt in.

again tape measure and a trip to the junk yard
find a 3.55 or a 3.73 ratio.

or find a T5 better yet do both

The 327, with an overdrive transmission, will give you what you want.

cm