Re: The rear axel blues!

Posted by DavidPackard On 2019/4/17 18:33:59

To answer 'kunzea';

Yes that's what I'm saying, but let's not forget the operating clearance. Measure how much the bearing cup is sticking out of the housing, add the clearance, and that's the total amount of shims needed. Remember in this procedure one side of the car has zero shims and there is a force applied to push everything to that side.

Once the weight of the car is applied to the tapered bearings the outer races should be pushed to the backing plate, and I don't see any force that would push it back away from the backing plate, so I believe for the rest of the car's life the outer cups will be essentially in contact with the backing plate, and the clearance is apportioned between the bearing rollers on each side of the car. The weight of the car also pushes both axles inboard, such that the thrust block is 'pinched' between the two.

I think the factory may have used the method you suggest, that is one side at zero, that is the bearing outer race cup neither proud or shy of the housing (this could be done with a fixture not a backing plate), and make a direct measurement of how much the other side's outer race is sticking out of the housing That's with some amount of force pushing all of the parts together, which could be a weight if the housing is vertical. Once you have that value the desired clearance would be added to compute the total amount of shims desired. That value is split 50/50, or as close as equal as possible, and shims and backing plates installed. Now all of that assumes that the thrust block can slide to the extent required by that simple procedure, but that could be checked before the process starts. I agree that is business of a 50/50 split of the shims is not totally required if you understand the thrust block can accommodate whatever the actual shim split will be.

OD, thank you for the kind comment. I understand the V-12 design that uses 4 total bearings. I think the applicability is for Packard rear ends that have a single tapered bearing on each side of the car. When I started working on cars the single bearing design had moved-on to a ball bearing design that didn't need shimming, and I think Rambler was the last holdout with the tapered hub design . . . another design industry set aside.

dp