Hi I ahve a slightly Noisy rear differential.
It is not too noisy, but I am wondering should I just change the Diff Oil ?
Is it safe to add Molyslip or some such product ?

Thanks...

Lexus GS300 1996

Is it definately the diff, or a wheel bearing? What kind of noise is it making and when?

[quote name='TigerFish' post='681150' date='Jul 13 2009, 09:25 AM']Is it definately the diff, or a wheel bearing? What kind of noise is it making and when?[/quote]

At about 40 Mph it is noisiest, when you slow down it sounds like grinding, not metal on metal but maybe rumbling....
at speed it is not noticeable.
I had a Ford once that made a similar noise and it was the diff, however that made a louder noise all the time...

DO NOT add molyslip etc products - do a yahoo search and u will se why - just like slick 50

[quote name='TigerFish' post='681150' date='Jul 13 2009, 09:25 AM']Is it definately the diff, or a wheel bearing? What kind of noise is it making and when?[/quote]


Ok the noise when you slow down is like a grinding motor winding down...

If that is understandable !!...

First check if the diff has oil in it,up to the level.[usually the filler hole]

Unless it's a diff. bearing, they usually whine either on drive or overrun

Jack the car up and spin each wheel to see if any run rough, to confirm it's not a wheel bearing

If you are certain it's the diff. try an oil change usually, EP90.

Look in the old oil for any metal fragments etc. if it still makes grinding noise, check your bank balance...

[quote name='ROYT' post='681803' date='Jul 17 2009, 10:10 AM']First check if the diff has oil in it,up to the level.[usually the filler hole]

Unless it's a diff. bearing, they usually whine either on drive or overrun

Jack the car up and spin each wheel to see if any run rough, to confirm it's not a wheel bearing

If you are certain it's the diff. try an oil change usually, EP90.

Look in the old oil for any metal fragments etc. if it still makes grinding noise, check your bank balance...[/quote]

What is the cost usually ?

One other thing to check quickly before condemning the diff is the resonators on the exhaust. If you look under the car pretty much in line with the back axle, there are two big rubber weights bolted to the exhaust (one one each pipe). If they come loose or perish, they make a really annoying noise almost like a propellor plane noise. Hard to describe exactly, but a propellor plane noise is as good a description as I can think of. Mine have done it before and had to be retightened as the rub washer on the mount had broken up and fell off. At the moment on one of mine, the rubber weight part is starting to come away and the noise has started again. Part no is 17581-46020 Damper, Exhaust Pipe.