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Differential issue??? #1410673
03/29/13 12:18 PM
03/29/13 12:18 PM
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Sac, CA
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mopowers Offline OP
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I just got my 68 Dart back on the ground with the fresh 8.75 with 3.91 gears and Auburn cone-type sure grip. Even though the cone weren't bottomed out, I machined the cones down .040" and installed .030" shims under the spider gears. I added a 7oz bottle of limited slip additive along with a couple quarts of 80/90.

I broke the gears in for 15 min on jack stands at idle in gear. There no noises, so I let it cool and drove it around the block. When I did so, the noticed that the rear chattered (I'd almost call it a clunking) when making turns.

Any idea what would cause this? It almost acts like a spool around corners or when a load is applied to it. I'd hate to tear this thing apart, but I will if I have to. I doubt it's the gears, because they don't make noise when it's up on jack stands.

Any ideas???

Re: Differential issue??? [Re: mopowers] #1410674
03/29/13 12:48 PM
03/29/13 12:48 PM
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JohnRR Offline
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Sounds like you put too much shim in that cone unit.

Re: Differential issue??? [Re: mopowers] #1410675
03/29/13 03:40 PM
03/29/13 03:40 PM
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Rio Linda, CA
John_Kunkel Offline
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It may take more time for the lube to get to the cones; try doing a bunch of figure-8's at low speed to distribute the lube.


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Re: Differential issue??? [Re: JohnRR] #1410676
03/29/13 06:34 PM
03/29/13 06:34 PM
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Sac, CA
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mopowers Offline OP
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I actually spoke with Auburn gear and Cass (Dr. Diff) this morning. Auburn said I used the wrong additive. I used the Trans-X tube I got from Autozone. They said it would be good to drain the oil and re-fill it with ford or chevy additive and 80/90.

Cass recommended taking it for a spin again because the lube may not have gotten to the cones yet like John said. He actually said it happens often with clutch sure grips. So that's what I did. I didn't warm it up on jack stands like I did last night. I just took it around the block several times making both left and right turns. Sure as $hit, it wasn't clunking like last night. It operated very smoothly. I'm just going to drive it and see what happens. Worse comes to worse, I'll pull the ring gear carrier and take the shims out from behind the spider gears. And use the ford additive when I reassemble.

I'll keep you guys updated.

Btw- Cass is the man. If any of you folks need rearend parts, give him a call. His customer service is second to none.

Last edited by mopowers; 03/29/13 06:35 PM.
Re: Differential issue??? [Re: mopowers] #1410677
03/30/13 01:50 PM
03/30/13 01:50 PM
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Posts: 75,095
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JohnRR Offline
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Quote:

I actually spoke with Auburn gear and Cass (Dr. Diff) this morning. Auburn said I used the wrong additive. I used the Trans-X tube I got from Autozone. They said it would be good to drain the oil and re-fill it with ford or chevy additive and 80/90.

Cass recommended taking it for a spin again because the lube may not have gotten to the cones yet like John said. He actually said it happens often with clutch sure grips. So that's what I did. I didn't warm it up on jack stands like I did last night. I just took it around the block several times making both left and right turns. Sure as $hit, it wasn't clunking like last night. It operated very smoothly. I'm just going to drive it and see what happens. Worse comes to worse, I'll pull the ring gear carrier and take the shims out from behind the spider gears. And use the ford additive when I reassemble.

I'll keep you guys updated.

Btw- Cass is the man. If any of you folks need rearend parts, give him a call. His customer service is second to none.




I don't know why you called Auburn , if you have a stock cone unit it was made by BORG WARNER , everyone calls it an Auburn but it is not.

Did you check to see how much backlash you had in the spiders after adding the shims ?

If you are going to tear it back apart to take out the shims you might be better off buying a better sure grip unit, if you can afford it. The cone type is a chip generating piece of garbage, every time you make a turn it is grinding itself to nothing .... why do you think the cones bottom out?? ... and filling the oil with tiny metal particles.

If you decide to keep it you should epoxy magnets into the housing below the oil level, and away from moving parts, to catch as many of the chips as possible and change the oil more than once every 100k miles ...







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