I just recently had an Auburn posi unit along with some 3.73 gears hear this humming sound coming from the differential. The sound is not loud at all. However, it was not there before. What could it posibbly be. Is it normal for for a posi or lsd diff.

 

when i got my eaton posi installed it also hummed pretty loud. when i would accelerate it would sound like it was winding up, then when i slowed down, it sounded like it was winding down.

someone told me that the gear was making the noise on mine.
i had a 4.10 installed.

 

The OEM Eaton G80 doesn't require an friction modifier additive (such as equa-torq) when using the synthetic oil. The auburn may require this additive to prevent "grumbling" so to say.

If you are hearing accel and decel whine your gears were not set up to be quiet. Quiet doesn't always mean better though...running tighter tollerances is better for higher HP applications.

Richard

 

Yeah if its whining on accel and decel, the pinion depth is too deep. If its not to bad it will wear in slightly and quiet down some but you will still hear it. If its really deep in the ring eventually it will prematurely wear out the ring and pinion. I would drive it for about 500 miles then pull the cover and have a look. Look to see how deep the wear pattern is on the ring. This is also a good time to change the breakin fluid and put in some good synthetic with a friction modifier. I found that the GM limited slip additive works REAL well for quieting down posi's and gears. Hell, once I had a posi that just wouldn't work and after I put in the GM additive, it would lock on command!

 

The noise is not annoying at all. You can barely hear it at around 45mph and only when you have your foot off your accel. Another concern I have is that synthetic lubricant was used. I thought Auburn posi units just needed regular lubricant. Is anybody inhere running synthetic with an Auburn posi unit?

 

When running synthetics it is usually the case that you do not use the addative but on my Impala I have an Auburn Pro 8.5 and I had some minor grumbling during sharp low speed turns but never any accel / decel noise ... How many miles are on ly gears? ... it may still be breaking in ... have you ran them hard yet?

Richard

 

I only have about 100ml on the auburn posi diff. By running it hard, do you mean gunning it or driving at a very fast speed. The fastest I have driven with the new diff is about 85mph and I have not gunned it yet.
Thanks for you feedback guys.

 

when i put in the posi on my old truck, i used to take it on the freeway and gun the ***** out of it. once it reached past 100mph, the truck sounded like it was going to blow up, pretty scary