My XK120 was modified in the early 60’s with a Salisbury 4H diff and disc brakes from a XK150. I had originally restored the car and all of the disc components but during the second restoration have converted back to original drum brakes. I am almost complete with the task, but am now puzzled after trying to check for end float on the axles.
I used all the original shims as they were on the disc setup, as I understand the caliper mountings took the place of the bearing retainer plates.
Put everything together and I’m not able to move the hubs (spoke wheels) in or out at all. Took the backing plates off today to check everything again, and even with just the axles sticking out of the housing I still can’t move either of them in or out.
I took one of the bearing retainer plates and set it against the bearing, and there is a gap between the plate and the flange of the housing, same as the three shims that occupied the space. The manual says to increase end float you add shims, but it seems like it has plenty of shim already.
I know I must be looking at it wrong somehow. Any ideas as to why I’m failing at this?
I don’t think that should have an impact. To adjust the end float, there would typically be a couple or three shims between the caliper bracket and the axle housing flange
Yes, there were two shims on one side and three on the other. Still want to know why with the hubs, brake assemblies, retainer plates, and shims removed I still can’t get any movement in or out. I can see that the outer bearing race protrudes past the axle flange about 1/32".
Nothing has changed except for the removal of the disc brake components. The rear end was rebuilt by a reputable Jag shop during the first resto, if I remember right they replaced the axle and pinion bearings.
I checked and it doesn’t appear to be any kind of a limited slip diff. Mike, you’re probably right about the bearing race. I assume I need to find a suitable slide hammer puller to pull the axle and bearing back a little bit?
With both rear wheels off the ground and the gearbox in neutral, turn one wheel by hand. If the opposite wheel turns the same direction, you have a Power Lok, if it rotates the opposite direction you have an open differential.
A Power Lok has two thrust buttons, one at the end of each axle shaft, that limit how far in the shaft can move. When they are originally installed, they are connected by an axial roll pin that holds them in place. Differential rotation between the axles usually breaks the roll pin in time, leaving them to rotate independently. So long as the axle shafts are not removed, the pins are captive. However, if you pull an axle shaft, the viscosity of the gear lube can pull the button out of its home. If it falls loose, it can block the axle shaft from being returned to its proper location.
Today I was able to move the bearing races outwards a little bit and what do you know, I now have some perceptible end float. Thanks everyone for the assistance.
There is a difference between the disc brake and drum brake grease seal retainers. The caliper mount serves this purpose on disc brake cars. The side opposite the seal is flat. On drum brake cars there is a steel disc backing the seal retainer. The back side of that disc has a raised flange. I believe the backing plate sandwiches between the seal backing plate and the axle flange and raised flange centralizes the lot. See the attached photos.
The thickness of the disc brake caliper mount is roughly 5.85mm (mine have been powder coated) vs 7.95mm for the drum brake seal backing plate (includes raised flange).
So do you have the proper thickness of shims to allow the tightening of the bearing retainers while maintaining the 8 thou end float? Also, the bottom 2 photos above have the bearing retainer plate reversed…the flange locates the backing plate on drum brake cars so it should face the hub.
I looked at that orientation very closely. I could find no guidance in the factory service manual advising on the correct orientation, and there is no corresponding ridge on the disc brake caliper mount that serves the same function. The only purpose I could see for the ridge was to register the brake backing plate with the seal assembly.
The illustration in the 120 parts catalog shows how it is all assembled. The lip on the bearing retainer plate fits into the backing plate.
What I did was to tap the bearing races outward using the opposite axle until I had just perceptible end float and the gap between the axle flange and the bearing races was close to the same for both sides. Then I just measured those gaps and fit the corresponding amounts of shim. Then I fastened the bearing plate tight with the shims in and checked the float again. Had to do this a few times but was able to get it close.
I did note that the factory shims were not to very close tolerances. For example the largest shim available is a .030", but I measured the ones I had at .029, .032, .037, and .038. The other thinner spare shims I had around varied as well.
Ahhhhh haaa. Here is one of those things where the various factory manuals give conflicting information. In addition to the various parts I had on hand, I consulted the rear axle section of two different factory service manuals, one an original Mk VII & XK120 (with the black/slate cover and silver print) and a modern reprint of the version covering Mk IIV/VIII/IX and XK120/140/150. Plate H1 (Salisbury Rear Axle Assembly) in both manuals show the plate in question (item #43, “Plate, retaining hub bearings”) between the wheel hub and the brake backing plate. Plate XL in the Spare Parts Catalogue (my copy is a XK’s Unlimited reprint) clearly shows the same part, tagged XL.43, part number 4HA-035, “Plate, retaining hub bearings” between the axle housing flange and the brake backing plate.
In the photo below, left to right: early manual > late manual > spare parts manual
