mittie

Hi guys. I am new here. I have a 2002 Z06. It has bee having a pronounced clunking noise when you accelerate and while changing any gear depress the clutch pedal. I replaced the clutch, the diff, I checked torque tube which turned out to be in a perfect shape. It did not help. At the beginning I found a loose rear wheel hub nut (not sure I name it correctly, it is that 32 socket size nut that holds the axle), I did tighten it up, it helped but the sound did not disappear completely. I have now idea now where else I should look? Could it be that splines on the axle or inside the hub are worn?
BTW I can also reproduce that sound not with the clutch pedal, but while driving on 1st or 2nd gear on lower revs, by rapidly pressing and depressing accelerator pedal.
Please advise on how to solve this mystery.

mittie

Guys, any ideas?

DetroitPlac

How's the engine and diff mounts look? Possible one of the mounts are shot and you're getting movement in the drivetrain. Or maybe the diff mount is loose/

killian96ss

When you tightened the rear axle nuts did you first remove the nut, push the axle in and lube the splines, or did you just tighten them? Did you install new nuts or re-use the old ones, and what did you torque them to?

Steve

mittie

At first I just tighten one axle, and it helped noticeably but not completely. Then when I was replacing my diff I pulled the axles out from the hubs completely. On the way back I tried to clean and grease the splines, and then put everything back together. I installed one new nut, and one is still old.
And I tightened to the maxim torque I have on my torque wrench which is I believe 150 lb.ft.

killian96ss

Sounds good. I did mine the same except I used new nuts and lock tight on the threads. If your torque wrench maxes out at 150 ft lbs you might not be actually be a 150, probably lower than that. Most torque wrenches are calibrated in the middle of their range, so they're not very accurate on the low or high end which is why I own 3 wrenches that covers everything from 10 ft lbs to 300 ft lbs. I would recheck torque with a wrench that goes to at least 250 ft pounds to be sure, but it sounds like you did everything right including the 150 ft lb torque. I believe factory torque was around 120 and the TSB said to use 160, so I went to 150 like you. I know those axle nuts can handle more as I've done some 4wd axle nuts which were about the same size to 300.

Steve

mittie

I can try to get a stronger wrench. But in general does it look like an axle nut issue, or I should search elsewhere?

killian96ss

It sounds exactly like the noise I was getting on my 02Z before I did the same procedure, so I would be absolutely sure those nuts are torqued 150-160, but it's possible there is still something else causing the noise. Did you check all the mounts as mentioned above?

Steve

killian96ss

The way you describe the sound above is exactly what mine did even the loading and unloading the drivetrain in 1st and 2nd. If that's not the problem it has to be something affected by engine torque. Could even be a bad bushing in one of the rear control arms that allows metal to metal contact.

Steve

mittie

I do not know how to look at engine mounts, I mean how to tell the are worn. But I replaced my diff mount with a custom built one, but the sounds it is making now are exactly the same as the sounds it made before I did the diff/diff mount job. So I think at least diff mount is out of the picture?

mittie

I actually changed all ball joints in my rear control arms, and the bushings looked perfect when I pulled everything apart.

killian96ss

Ya, make sure those nuts are tight enough, then go from there.

Steve

mittie

But is it possible that the splines of the axle and/or hub could be worn enough to cause such a clocking noise when the nut is not tighten enough for a some time? Or could the CV joints of the axles be worn?

killian96ss

Yes it's possible the CV axles are worn since they are like u-joints. How many miles on the car? If you can get one wheel at a time off the ground you can check for excessive play, but you'll also be feeling some play in the diff as well, so it might be hard to tell unless there is an obvious difference from one side to the other. That pop/clunk noise is actually the back of the hub slipping against the face of the CV axles where they mate together, but if the axle nut is tight enough there shouldn't be any movement between the 2. That's why I suggested making sure those nuts are at 160 ft lbs. If that doesn't work you can at least rule out the hub/axle slipping against each other.

Steve

mittie

I tried to check the CV joint while axles were taken out, they seemed to be rock solid, the car is 80k miles.

Bill Curlee

Why don't you get an assistant to help you torque the drive train while you look at all the drivetrain parts and see if you can see any LOST MOTION somewhere. Chock the wheels, have the assistant load and unload the drive train by controlling the clutch peddle.

You can also check the differential belleview springs that put preload on the limited slip clutch packs inside the differential.
Jack one wheel off the ground. put the trans in N, release the park brake. Attempt to rotate the wheel off the ground. If the clutch packs are good and the spring is not broken, there will be a torque resistance (something like the E-brake being set in a light drag) in either rotational direction. If it is very easy to rotate, BROTHER, you have problems with that clutch pack.

Do the same procedure to the other wheel. They should be very similar in the amount of resistance that it needed to rotate both wheels.

While the wheel is off the ground, do a PUSH - PULL test on the wheel to see if you have ANY slop in the wheel hub bearing. Push Pull at the 3 O Clock/ 9 O Clock & 12 and 6 O Clock positions. A good serviceable wheel hub bearing will have little to not SLOP.

Bill

mittie

Ok, I tried to wiggle the car on gear back and forth, it seems that sound is coming from the rear end (either the diff itself of the axles), so it is not engine mounts. I scheduled an appointment with an independent mechanic this Wed, will see what he will tell about it.

Leftlane_1

What did you find out?

mittie

Ok so since then I put my old diff back in place, it still whines but there is significantly less clunking noises, virtually none, although the slack in both diffs seemed to be the same. So it is related to the diff, not sure what exactly is the reason, maybe the splines on input or output shafts were worn on the rebuilt one. Any way I bought the whole transaxle with the gearbox, did not put it in yet. Will update after I do.