The Stovebolt Site Forums The Shop Area Engine Shop Help for a friend

Ok gang, here's the deal. I visited an old friend over the weekend. We were good friends as teenagers, but like a lot of people, we lost touch as we got older and we just kinda went our seperate ways for about 20 years. I recently learned that he lives about 2 miles from where I live so Sunday I decided to give him a call. He invited me over to his house and we had a great time talking about the "good ole days".

Well, as it turns out, he is into old chevy trucks also and he is in the process of working on a '54 3100 that he bought about a year ago. The 235 that was in the truck wasn't salvageable and he has decided to replace it with a 350 that he has already reworked and another 3 speed trans for the 350 (not sure exactly what it is).

My question is this, will he need to also change out the old rearend?

I don't have a clue when it comes to this sort of thing and he never mentioned it, but I seem to recall reading a post somewhere concerning this subject, something about the gears or whatever will not hold up to the rpm's of the larger engine. Any help on this subject is greatly appreciated. I don't want to see an old friend put all that work into fixing this truck only to find out later that he should have changed the rearend before hand. Thanks

A '54 3100 should still be a closed driveline, unless it has been modified already. If the torque tube rear end is still there, he will need to switch the engine, transmission, driveshaft, and rear end.

The entire truck was still original; engine, trans, torque tube, etc. He has the driveshaft that goes with the new 350 engine and trans but I think he is under the impression that he will be able to use the old rearend. Guess I should tell him it will need to be swapped also.

I am by no means a mechanic...just know how to tune a 235. But this whole rear end thing taxes my little brain!! Why would the rear end need to be changed? Is it because of the RPM's of the larger motor? It won't hold up?
Can you take the rear end out of ANY 235 driveline and put it ANY other 235 driveline without changing the driveshaft, tranny, etc.?
This whole rear end thing has me confused!! :confused:

The older chevys before '55 had a enclosed driveshaft that was factory riveted to the rear end housing. Its called a Torque Tube drive. The prop shaft rides on brass bushings inside the torque tube. The front end of the enclosed driveshaft bolted to the back of the transmission. This transmission/b-housing won't bolt to any engine '63-newer. The 216s, 235s and 261s will fit the bellhousing. So you can swap 235/261s out and retain the transmission and rearend. The 55-62 vehicles w/235 have open driveline (the R/E you're used to) but similar bellhousing/tranny. So 55-62 vehicles can retain the same rearend when swapping engine/trannys.

Later straight 6s or any V8 will not bolt up to a pre-'55 chevy. So if you change from 235 to a V8, you change transmission. If you change transmission, you've got to change driveshaft and rear axle. This is why engine swaps into a '55-older chevy require complete changing of the running gear from engine to rear axle.

chip

As you guys can tell, I don't know squat about the old trucks except the fact they are cool. That is why I love this place, I can come here and find out anything I need to know.

I have never owned anything older than my '70 C10, but I plan on finding an older model one day when I finally finish the one I have.

Thanks Gmc and Chip for the much needed info.

If your friend does not want to change the rear end he will have to use the original trans. He will have to use an early chevy cast iron bell housing. They have mounts at the bell housing. The 55 thru 59 truck would be best as I believe the mount to the crossmember is the same as the Advance Design trucks. Also the truck bell housing bolts through the bell housing for the bottom two transmission bolts. If he uses the stock bell housing, he can use the stock early front mounts for a 59-59 truck, and fab a simple front crossmember.
In 1969 I had a 49 GMC with a corvette 283 in it. I ran it hard and street raced it a lot. The rear end held up with no problems, although I did break the U-joint once. Not really the U-joint, but the splined portion of the joke. My truck was a 4-sp model. I do not think the stock 3-sp will hold up to anything more than normal street driving.
Hope this helps.

Chip
Fantastic explaination!!! Even I understood what you were talking about!! Thanks for the help.
Tony