VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 38 differential setup

Anyone rebuilt 38 differential ? my gears are good but torque tube up front is damaged near spline so need to replace torque tube,hate to take mine apart maybe never get it back to specks again..instructions needed ?

Easiest way: find another center section. Chevrolet never meant for the torque tube to be taken off.

I read in some service manual that they felt is was impossible to get the tube lined up correctly in the field, and misalignment would cause premature failure.

Another way: cut and splice the torque tube. That way you only need a donor torque tube with the right size and shape at the front. It can be the wrong length, meaning some other years will work.

Ray Waldbaum spliced a torque tube when making a custom 37 rear to fit in a 36, and accept later gears. His article is posted here:

https://vccachat.org/ubbthreads.php/topics/334876/1936_Chevy_3.55_rear_gear_conv

Do you like your current gears? If you are going to go to the trouble of cutting and welding anyway, I would do what Ray did, and set it up with the later pinion spline. That way, you can have 4.11, 3.70, or 3.55 relatively easily.

You wouldn't have to do anything to the axle housing or axles, only modify the center section and torque tube, because 38s already have hypoid gears. (The 36 is spiral bevel, and that is what made the axle housing change necessary in the article.)

By far the cheapest and easiest way is going to be just to find another center section and torque tube assembly from a 38. The costs of rebuilding one of these rearends spirals out of control quickly. The bearings are old and weird, and you will probably find some questionable ones, and wind up replacing all of them. 3 of the four were pretty expensive on my 36, as they are no longer available through bearing stores, napa, etc. Filling station should have them.

If you can find the center section from a 38 with the leaf spring front end, I think it has higher gears, something closer to 3.70 instead of 4.22.

To do a stock rebuild (if your torque tube wasn't bent), all you need is the service manual, and it is online here:

http://chevy.oldcarmanualproject.com/shop/1938/index.html

One thing I would add though, if you are planning on reusing your gears, check the backlash and the contact pattern (as shown in the manual) BEFORE you take it apart. With used gears often you need to set the backlash very close to what it was to get a good pattern (rather than what the book says. The pattern is all important. Checking this beforehand can save you a lot of setup time later.

Good info bloo.

I wonder if you might be able to get the damage repaired? I've had driveline shops cut/paste various shafts together, balance and straighten shafts so they might be able to repair yours...

The front 3" of torque tube has been smashed but still turn OK ..I thought about cutting off 3" with pipe cutter and welding my doner piece on,its the part that the sliding bell goes over so its has to filed down..Does the u-joint go in the recess at end of tube? sc

If your doner tube is OK, I would pull everything apart and use it. It is not that complex a job to do. I would measure the existing backlash and document it. The important part is to get the mesh pattern exactly the same when you reassemble it.