8-3/4 Posi Whining......

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pastortom1

pastortom1

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I picked up a Demon with a new 8-3/4 Posi rearend (3:55 gears).......the rearend looks brand new, used very little as advertised.....quiet when cruising.........BUT,

When you back-load the gears by letting off the gas, they whine......quite loudly......I don't know if the gears were maybe not shimmed properly, or just need some better lube or an additive............

This is quite annoying and noticeable........like an old truck........

Pointers?
 
It sounds like the preload isn't set correctly and the ring/pinion gears aren't meshed in the proper fashion. One thought - are you sure the noise is from the rear gears and not a bad U-joint or wheel bearing?
 
My 4.10's whined for about 200-300 miles when they were first put in....had to get broken in. I'd check the mesh pattern to be safe.
 
I've never heard a U-Joint sound quite so loud......usually they growl before they go....this does sound like gear noise, always "in tune" with the rpm's too......

I'm going to check the lube level again today just to be sure it's getting enough..........

I'd appreciate someone telling me what should be a fair price to get the gears adjusted properly if they're out a little........Too difficult for me here in my driveway..........

ALSO, has anyone heard of an additive derived from "whale oil" for these rear gears?
 
The "Whale Oil" is the Mopar limited slip lube.....it's in a small bottle. Just go to the dealer and ask for some limited slip additive that's the Whale Oil. It cost me $80 to have my rear set-up but I supplied the gears, install kit and I pulled the third member and took it to him.
 
The pinion gear in coast mode loads the outer (small pinion bearing). It could be that this bearing has a problem since the noise is in the coast mode only. In power mode (applied throttle) this loads the inner pinion bearing which would lessen the pressure on the outer bearing making it quietier.
 
Sometimes if I take the wife out to dinner, or leave my wallet lying around she'll stop whining. Maybe give the rearend a pat on the head and a drink of Sure Grip additive to see if the helps, although it may have no "bearing" on the matter. :)
Seriously though, I think 340mopar hit it with the outer pinion bearing theory.
 
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