wierd gear oil question

[DaytonaBlues]

I got a 99 z28 that has a heavily abused stock rear end in it with the torsen type diff. Im suspicous of it now because im hearing clicking under acceleration, (but not around corners though wierd). I do have quite a bit of in and out movement of the rear wheels when off the ground
(you can push them in and out and theres movement, which i assume is just the c clips).
also have some slight play when you check the rear wheel bearings
(tire and wheel have play when you grab at the 12 and 6 o clock and the 8 and 3 oclock)

i have 75w90 castrol synthetic gear lube with the GM additive in it now. i was told i could swith over to some 80w140 Lucas non synthetic with no additive to help with the diff noise. is this true? it is the gear type diff. im only considering this because of the clicking i have under acceleration, and some vibrations which are probably unrelated. last time i had the diff cover off i didnt see anything unusual but then again i didnt really know what to look for..

[cammed goat]

Have you checked your U-joints as well as your pinion yoke where the driveshaft and rearend meet? You could have looseness there as well. When you had the diff cover off, did you notice any large metal particles? I only ask since you mentioned vibrations which could mean worn pinion bearing. Most members on here will advise your rearend is not worthy of servicing as it is too weak from the factory.

[pajeff02]

Gear oil will not fix the problem. Better to pop the cover and see what is going on in there. You should not be able to significantly push the axles in unless you first remove the center spacer.

[DaytonaBlues]

thanks for the tips. I replaced both ujoints as well as the clutch and flywheel, all have less that 200 miles on them. as for the pinion yoke, what do i check for? up and down play i assume? i did have the cover off to put in the castrol synthetic and the magnet didnt have any huge chunks on it, and there wasnt anything abnormal looking.

as for the axles yea they cant be moved all that much fore and aft, meaning wheels off the ground the wheels can be moved a TINY bit in and out. there is a vibration at hiway speeds, its not much but its there. you notice it especially in say 4th at around 45-50 mph. i was thinking rear axle bearings simply because there is play when you check them like when you check front wheel bearings. i never have really thought about pinion bearing wear. how do you check it? pull the axle out then move the pinion shaft up and down etc?????

[SteveC]

I have been using 85W-140 dino oil now for over 11 years with no problems whatsoever. Even though this will not solve your problem, the thicker oil will help dissipate the heat more efficiently.

SteveC

[cammed goat]

With the car on a lift or rear on jackstands, see if you can push up on the driveshaft. If the driveshaft moves upward while you push up on it, you have play and a worn pinion gear/bearing/seal and the rear is most likely toast. Also look to see if you see some gear oil leaking from the front of the differential.

[DaytonaBlues]

With the car on a lift or rear on jackstands, see if you can push up on the driveshaft. If the driveshaft moves upward while you push up on it, you have play and a worn pinion gear/bearing/seal and the rear is most likely toast. Also look to see if you see some gear oil leaking from the front of the differential.

so basically what your saying is that if i can move that driveshaft a bit up and down the rear end has had it, and not even replacing that pinion bearing is gonna save it?

[pajeff02]

Define "a bit". Usually, if the pinion bearing is shot you can feel it by turning the differential by hand (with the driveshaft removed and the car in the air). It would have to be wasted for there to be enough play to wiggle it like Cammed posted. The stock rears are known for tearing up ring gears, axles bearings wearing into the axles, and the pinion seal weeping.