Noise on decel, some kind of rattle.

Dec 10, 2013
Kuala Lumpur ,Malaysia
The whole story is, my diff (RWD) had a mild clunk when shifting from N to D and from N to R, or P to R. It also had a whine when engine braking long downslopes.
Since Mk3 Supra/Gen2 Soarers are notorious for crush sleeve issues after decades of use, I decide to rebuild the diff with a "pro". He changed all the bearings to new ones , but he reused the crush sleeve and carrier shims. When i got the car, it was roaring on accel and decel.

I sent it back to him and he claims the side shims are too tight, so he cut down one shim by 0.05mm, While the accel sound did quiet down, the decel sound was still there, its like a rattle. After about a month of driving, I got fed up of the noise , and drained the oil. It was loaded with gunk and turned blackish yellow, the magnetic drain plug had black fine gunk, indicating gears were grinding.

I decide to take apart the diff myself and check for pinion preload, there was none. So I bought a Weir crush sleeve eliminator and proceed to set up the correct pinion preload. I looked at the ring and pinion and it looked ok to my eyes. I set a good backlash and carrier preload, and acceptable gear pattern on both coast and drive side, and put back the diff.


To my horror, that rattling on decel is still there. I also tested with the car coasting in N, yet the rattling is still strong. If the car coast in N, it means the pinion is driven purely by the ring gear, and it rattles like hell.
On accel all is good, while there is some hum on accel at some speeds like before, it is nothing unacceptable. The problem is all on decel /coast.
So my question is, is this the ring and pinion itself ? Should I get a new gear set and rebuild ?
The CV shafts are ok with imperceptible play.
Center support bearing is new, U joints are rebuilt and rebalanced.
Logically ,if its the other components (CV axle, U joint , wheel bearing) causing noise , it should be having that rattling sound on accel too.
Is my conclusion correct ?
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