Rear differential whine?
 

Hey guys,

I went to Enrique's shop on Saturday morning to get a replacement differential put into my 300DT as well as some other misc stuff. All was fine and dandy until I got up to freeway speeds. Around 45mph and upwards, there is a distinct whining sound from the rear of the vehicle. Its even more pronounced because the back seat is out. I only hear the sound when I depress the throttle. It immediately disappears when I let go. Is that a classic sign of a differential that's worn out? Will adding new gear oil help? Or is that a bandaid for the true cause of this noise?

Bob

bump for monday morning crowd. help!

I don't understand- this is the replacement differential that is whining?
A whine from the rear is, yes, probably the diff.
Wheel bearings make a moaning or grumbling sound (gotta love descriptions of sound), and would not let up with your foot off the accelerator.
Axles make a nasty thumping (ask me how I know).
If you got a replacement, chances are the fluid level is good. Adding more will not help. Some folks like to put a thicker fluid in there (straight 90) to reduce the noise some. But it probably won't get rid of the whine altogether. It's a worn differential when it starts whining.

whine under load is classic ring gear wear... I hope you didn't pay much for the diff.

Worn gears, or improperly set gears. Did they replace the internals or the whole case with internals?

Probably will run 100,000 more miles if there is good fluid and no significant backlash/play.

How do you determine play in a diff? Remove the DS and axles?

I've always determined play by grabbing the rear driveshaft and trying to rotate. Some don't budge, some can turn almost a half revolution into the diff. A diff with a lot of play often clunks when you put the car in gear, as the shaft rotates before the diff locks into its gearing.

Thanks for the info guys. I confirmed this with Enrique over the phone who just ordered another replacement diff for me. I"m going to get this installed sometime this week or by Sat. I'll update the thread later