Differential Question

[TR4]

Ever since I bought my TR4 back in 2002, I have lived with what I believe is a little slop in the differential. When I let off the gas, I notice a slight klunk from the rear of the car and I hear that noise again when I get back on the gas. I realize the rear pads might also be sticking. Here is my question, is there a simple test to tell if the differential has too much slop and needs to be repaired?

I will add the U-joint is new. I replaced both of those thinking it would eliminate the clunk sound but it did not. I also replaced the shocks a while ago but that did not help with the noise either.

 

[TR3driver]

Checking the slop is fairly easy; one method is to put the rear up on jack stands and, with the handbrake set and the gearbox in neutral, see how far you can turn the driveshaft. This is also a good test to spot a bad rear U-joint (which might also be the problem) and/or a loose flange (ditto).

The question is how much slop is acceptable. My TR3A rear end was pretty loose when I got it in 1984; 20 years and perhaps 200,000 miles later it was still pretty loose but still working fine.

While they aren't terribly difficult to rebuild, it is a LOT of work. Just getting it out of the car is a PITA, especially since it runs between the frame & body.

You might also check your rear shocks; mine tend to work loose against the frame and cause clunking noises.

 

[Geo Hahn]

...put the rear up on jack stands and, with the handbrake set and the gearbox in neutral, see how far you can turn the driveshaft...

And how far is normal?, how far to call it pretty loose?

 

[TR3driver]

After I rebuilt the Stag diff, I got only a tiny movement; perhaps 1/8" at the surface of the driveshaft or less. I'd guess the TR goes a 1/4 turn, but it's been awhile since I've checked.

Most of the slop appears to be in the curved thrust washers that carry the spider gears. They are copper alloy (hence can be attacked by hypoid oil with the sulfur additive) and are supposed to be selected for some small clearance (don't recall offhand, but it's just a few .001"). However I only found one size available, which happened to fit fine (coincidence?).

 

[TR4]

After I rebuilt the Stag diff, I got only a tiny movement; perhaps 1/8" at the surface of the driveshaft or less. I'd guess the TR goes a 1/4 turn, but it's been awhile since I've checked.

Well, the driveshaft on my "4" will freely move about 1/4" back and forth at the surface. Could this be the source of noise around the rear of my car? I tried to see if I could make the noise by spinning the wheels when I had it up on jacks. I could only get it to make a very slight noise. I assume it would be louder under load. It sounds like the shaft causes the noise when it catches after spinning freely. Any real cause for concern? I have driven it like this for 7 years and it has never gotten any worse. Others do not notice the noise when riding in the car unless I call it to their attention.

I also checked to see if the rear pads were sticking and they are not.