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Discussion Starter #1
Guys I finally got my engine back together and running right. I raced it yesterday at the GM M7 event and actually placed pretty good (lost due to tranny trouble in the quarter finals - crap). BUT. A friend told me that my drivers side rear tire wasn't turning during my burnouts at all and that it was still wet and spun when I launched the car. My 60' times were crappy (at least they were consistently crappy) compared to usuall and I had no rubber stuck to the drivers side quarter either.

Here's what I'm running:

Original 1968 8.2" 10 bolt.
3.55 Richmond gears.
Auburn pro series posi (Eaton wasn't making them when I built the rear)
all new Timken bearings (1.5 years old)
85w140 Stalube oil with one can of posi additive (its been in there over a year)

Any ideas? I'm thinking the clutch pack is shot, there's no clicking noises or anything else weird going on.
 

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From what i hear, auburns cannot be rebuilt.
Personally i think you should ethier buy an Eaton, or build another rear, like a 12 bolt and use Ford style housing ends, and an Eaton posi.
I'll be able to tell you how mine works out soon
 

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You should contact Auburn...a while back they had stated that they may offer rebuild services on an exchange basis. This was a couple of years ago so they may be doing it now.
 

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Auburn has an exchange program. You turn in your old unit and they sell you a new one for what it is supose to cost to rebuild a Eaton. The problem with the Auburn is that when it wears it fills the rear end with powdered metal. When you remove it be sure to check the axle tubes and all of the other places where this metal settles.

It really doesn't matter what kind of a posi you have, they don't do well in water burnouts. I have seen Eatons, Traction locks, Auburns and others do the very same thing you are describing. A posi is designed so that the differential gears apply pressure to the clutches under a load. The preload springs are just there to help get things started. If there is not enough traction the gears can not apply enough pressure to the clutches to lock up. Once the clutch starts to slip it overheats and just gets worse. This also cooks the oil, so bearing and gear failure are next. If you leave out the posi oil additive it will help the clutches lock up, but your Auburn may be too far gone already.

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'69 RS/SS396 pro street
427/4spd/9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead
 

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Discussion Starter #5
That's very good to hear about the exchange program. Especially if its a lot cheaper than buying a new one outright.

Big Gear Head, if I got another Auburn, could I do the swap without pulling the pinion and setting lash, etc? I've pulled carriers before but have never set up the gears. Maybe I could just swap the posi unit and check the gear mesh with some marking compound?

ps. drained the oil this afternoon, didn't see anything that looked like metal in the oil. Just stringy thick oil with a faint green tint to it.
 

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Use a dial indicator to check the backlash before you remove the differential and set it back exactly the same when you install the new one. Most of the time you will have to change the shims a few thousandths due to machining tollerances.

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'69 RS/SS396 pro street
427/4spd/9"
Byars Performance
High Performance Drive Train Parts And Service
www.lubedealer.com/biggearhead
 

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Do the driveway test.......
Make sure both tires have the same air pressure in them, level ground, power jack it and see what you leave for black marks.
What was your 60' times?

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Y2K YELLOW C5
BEST TIMES W/ BALD @#% EMT's & POWERLOADER II:
60'=2.02
1/8=8.54 @85.69mph
1/[email protected] (3,470 lbs. race ready)
1999 GMC SHORT BED SLE
1996 IMPALA SS (4,360 lbs. race ready)14.82 @ 92.59 MPH
1972 ELCAMINO (UNDER RESTORATION!)
1968 CAMARO COUPE (3,490 lbs. race ready))13.80, 1.94 60' & 100.44 MPH
1966 Mustang Hardtop (UNDER RESTORATION!)
Vice-Chairman, Virginia Section of SAE.
Link to my 10/12 bolt conversion http://temp.corvetteforum.net/c5/30s/temp_pictures.shtml
 

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Discussion Starter #8
Thanks Big Gear Head, I think I understand.

I called Auburn this AM and the exchange program will cover their units out to 4 years old. $85 outright for a new unit, $100 with shipping. If it goes out again, I may opt for the Eaton and use the 800# springs to save future hassel, but for now I can't beat $100.

Driveway Test
It was obvious at the track they were not spinning equally, so I don't think I'd be pissing off my neighbors. LOL

60' times were high 1.7's and low 1.8's (usually mid 1.6's). 60's got slower as the day went on, with my last pass 1.899 secs.
 
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