VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 drive shaft

Hello all
I have a problem I cannot solve and I hope someone can help.
I had occasion to replace a universal. When I dropped the drive shaft/torque tube, it immediately moved to the side of centre.
Viewed from the rear, it looks to be about 3 inches to the left of the centreline.
When jacked up, the shaft is not quite on the centreline and to make the universal fit into the yoke on back of the gearbox, it has to be forced to the right.
My question is, does the shaft have to be exactly on the centreline so that the universal makes an easy fit into the gearbox yoke??
Any help and advice would be appreciated.
any thanks
Ron

I would check the rear springs(center bolt). Maybe something wrong there.

Ron,

I would think that if your spring bushings and the spring are centering seat pins then the differential will be centered as well. The engine and transmission mounts could be distorted some, as well.

If you are having to force the troque tube over three inches or so then I think you have a matter that needs further inspection. Something will be binding. Are the springs leaves in their right place or are they shifted against the keepers?

Make sure the car is not dog-walking. Or whatever you call a dog down there.

Best,
Charlie

Ron,
The simple answer is that the drive line should be in alignment. Any side force will quickly destroy the U-joint.

There are several places to check including a bent torque tube. Accurate measurements will point you to the problem(s).

If you have the car jacked up by the frame on one side it will do this.

Support the frame (let the rear axle hang) and loosen off the spring to diff mounts so you can move the tailshaft back in line with the gearbox rear. Have a look at the spring to axle mounts, you may have a problem there. I found one of these cracked in two and seperated by about 1/4". That small amount at that point will lead to a misalignment of a few inches at the uni joint.

(Here I go again. Stepping over the traces.)


Chipper,

You wrote "The simple answer is that the drive line should be in alignment. Any side force will quickly destroy the U-joint."

When I saw that i shook my head but didn't then respond. Here is my problem with the statement:

a. While it may play havoc with some things like the transmission mount and the springs and tires and cause the car to "dog-walk," if the U-joint
housing is hooked up and the bolts in place, I don't see how the U-Joint can be adversely affected. That is why it is a U-joint. It will flex on 360 degrees up to its limits.

b. The U-joint is there to flex with the torque tube. The tube is already flexed down and will flex up and down when the alignment is correct.

c. The U-joint will flex to the side and in any position subject to its limits.

d. Too much side force may destroy the U'joint but not merely any side force

Accordingly, I doubt the minor misalignment in the instant case will bother the U-joint any at all.

Respectively,
Charlie

Well, well Charlie. Obviously you have never had an old Chevy with a bent torque tube. I have! I initially thought as you did that a little side force wouldn't affect the U-joint as it was designed to operate with some misalignment. Well I fairly quickly found out that there was enough force to move the ball housing to the side and offset the transmission output shaft and torque propeller shaft. That wore the U-joint (was NOS when installed) and produced an increasing vibration until the torque tube was straightened and U-joint, propeller shaft replaced. Even wore the spline sides on the propeller shaft to be a bit tapered instead of parallel. An expensive lesson.

In case anyone is wondering the U-joint is only designed to handle an angle in one plane. A constant velocity joint can handle two planes.

Well, well, Chipper,

He didn't say anything about no stinkin bent torque tube. Surely that imperfection would have been obvious to him.

All I'm saying is that if the U-joint housing is mated up to the receiver, the U
joint will handle a mere up to three inches side pressure needed to get it there.

And, the U-joint will handle the plane created by an off-set differential because there will only be one (plane) as long as it is fitted in the housing. Sounds like you had an entirely different problem. Many cars go down the road just fine with a misaligned differential.

It seems to me that your experience was much more extreme than that was described in the instant case. (see dog-walking)

Whatever. I'm sticking to my guns on what i've said and think your quoted statement "of any side force" housings was too all inclusive inasmuch as it didn't take into account that the problem might not be a bent torque tube.

Mostly, I am taking exception with the word "any."

Best,
Charlie