Changing rear drive in a 40-56s

[Guffin]

When I bought my 1940 56s i got an extra rear 1:3.9 drive, complete with housing (differential carrier) but without the torque tube. The seller said it was adjusted and "just to bolt on".

On this car the torque tube is bolted to the differential carrier (pressed on on older cars). Looking in the Motor's repair book it reads "Never unbolt the torque tube because they are matched and aligned during production". Still, there is a picture showing the differential carrier without the torque tube (with the propeller shaft). Under the picture reads: "Checking propeller shaft run-out". Perhaps it is not so bad to unbolt the torque tube?

To me it seems more easy to install the complete unit rather than installing the pinon and ring gears alone. But in order to install the complete unit I have to unbolt the torque tube. Is there any danger doing this and how can I be sure the alignment is correct when I put on the torque tube? Has anubody experience doing this?

All advice are welcome. Thank you.

Jan

[The Old Guy]

In order to install the ring and pinion, you must remove the drive shaft anyway. The torque tube unbolts, and the drive shaft is pinned to the pinion with a splined collar. The collar is sometimes VERY stubborn to remove. After installing the drive shaft on the new rear unit, you can put the torque tube on ,and see if the drive shaft runs true. If it does not, the you need to bend the drive until it does run true. It isn't easy, but if it does not run true, it will vibrate like mad. I did this to my 40, and it took three tries to get the vibration out.

[Guffin]

Thank you. Is there no risk of having the torque tube misaligned as they warn for this in Motor's?

What is the best way of pulling the splined collar? Using heat? I guess it is not possible to use a puller of any kind.

In Motor's there is a description on how to check the propeller shaft run-out before the torque tube is attached. It must be less than 0.015" at the torque ball end, according to Motor's. That is not much.

I wish somebody could help me with this work but here in Sweden no shop is willing to work on such an old car. I have done a lot of engine work on my Hupmobile but that was when I was young.

Thank you,

Jan

[The Old Guy]

The torque tube bolts up the the rear end. and if the surfaces are clean, you should not have any misalignment. ( at least I have never experienced it) To remove the splined collar, you need to knock out the pin and what I did was heat the collar and using a "big" (one inch by 16 inch)brass drift, and a BIG hammer. I blasted it a good one, and it came off

The big job is getting the drive shaft to run true

[Guffin]

The old Guy, thank you. You have helped me before. I am new to the 1940 Buick so it is nice to have friends to ask.

A second problem for me is space. My garage is too small to take out the whole rear end. Can the work be done with the torque tube still attached to the gearbox? Or perhaps I should wait until next summer and do it outdoor.

Jan

[The Old Guy]

The rear end MUST be removed from the car.even if you tried to leave the torque tube on, you would still need to remove the rear end to get the drive shaft off.

[Guffin]

Now it is done! I learned that a brother to a friend of mine had a complete workshop for cars and I could borrow it and even have some help from the retired owner. We managed to push on the drive shaft on the pinion shaft without loading the pinion bearings. This was done by pulling against the big nut on the pinion shaft. It went very smooth and we didn't have to use heat. At the same time we cleaned the bearings and changed all oil seals to modern rubber seals. We also changed the torque ball seals, the u-joint and bushing. To our surprise the seal at the u-joint rear end was missing but oil had not been leaking down the torque tube, probably because the torque ball was leaking so badly.

Jan