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Do I need to dump the fluid again?

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Old 02-10-2018, 09:26 AM
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Default Do I need to dump the fluid again?

I changed my posi unit, axles, seals and added new fluid in my stock 10 bolt, the ring and pinion was not changed. Do I have to change the fluid again after a certain amount of miles? Thank you.
Old 02-10-2018, 11:31 AM
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What year is the car ?
Why did you have to change the posi unit ?
What posi unit did you put in ?
The ring gear was removed from the original posi unit and put on the new posi unit. Did you go with new carrier bearings ?
Did you check 'lash' ?
Did you use an aftermarket cover to be able to drain the fluid without having to remove the cover ?

If you put in an Auburn posi(metal cone clutches),I'd recommend changing the fluid. The 'break-in' of the Auburn's clutches will put those particles into the fluid.
Old 02-10-2018, 06:51 PM
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Originally Posted by FirstYrLS1Z
What year is the car ? 1999 Trans Am A4, the 2.73s upgraded to 3.42s preivously. 115k miles.

Why did you have to change the posi unit ?
I was hunting a vibration and there excessive play when rotating the wheels back and fourth while the car was on a lift in the air. Also, something metal was banging when I would go over a bump which is now gone. The play is also better but the vibration turned out to be uneven permanently flat spotted tires.

What posi unit did you put in ? I wish I remember, I was put on the phone with the tech guru @ Quick performance in IA (recommended by a friend). He said he knew what I had and I purchased an assembled posi kit. I believe it came with the bearing kit because it was around $400 bucks for the parts. It was a rush to get the parts because the car was stuck on the shops lift.
The ring gear was removed from the original posi unit and put on the new posi unit. Did you go with new carrier bearings ?

I don't think the ring gear was removed but I did not see the actual install, each time I went it was still in the car.

Did you check 'lash' ? I am assuming my mechanic did because it feels fine and there is no whine or humming that I hear.


Did you use an aftermarket cover to be able to drain the fluid without having to remove the cover ? Yes

If you put in an Auburn posi(metal cone clutches),I'd recommend changing the fluid. The 'break-in' of the Auburn's clutches will put those particles into the fluid.
I guess since I have the aftermarket cover I should have it changed, I am so pissed at myself for not knowing which one I bought. Thank you for taking the time to ask detailed pertinent questions. I am smart enough to know I am not mechanically inclined and I needed to have a professional do the install.
Old 02-10-2018, 07:42 PM
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1999 TA with an A4,3.42 gears,and a CircleD 3K stall is a good combo.
1999 TA would have come with a Torsen posi carrier,it would be nice to know what the replacement posi/carrier is.
The ring gear would need to have been removed from the previous posi/carrier and installed on the replacement posi/carrier.

Since the car originally had 2.73s',which would have been on a 2series posi/carrier,3.42s' would have required a 3 series carrier OR the use of a 'thick' 3.42 gearset. This is just info being passed on and has nothing to do with current.

'There is no whining or humming'-that is good

'there excessive play when rotating the wheels back and fourth while the car was on a lift in the air'-since it was the original Torsen posi/carrier probably used for the 3.42 gear swap,that excessive play is typical of a Torsen. They have that 'excessive play' when new. Play on a torsen needs to be checked by rotating the driveshaft and watching the play in the rotation of the wheels. It's a common misconception when trying to evaluate a Torsen by old school mechanics that are used to Eaton and Auburn posi carriers. This is not intended to 'belittle' the shop/mechanics you used.

'I don't think the ring gear was removed but I did not see the actual install, each time I went it was still in the car.'-did you happen to take a pic of the new posi/carrier ?
Old 02-10-2018, 08:13 PM
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You have me really curious so I am going to email Quick Performance and see if they can pull the invoice. Thank you for all of the knowledge, I will let you know in a day or so what they said.

Side note:
I got a diff from a stick car that had the 3.42s in it so I guess I do have a 3 series carrier.
Old 02-10-2018, 08:41 PM
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The 3.42 posi/carrier would then be either an Auburn from a 1998 or earlier OR a Torsen from a 1999 and later.

I work on rear ends,since the 60s'. But now it's just the little F-body 7.5/7.625" 10 bolts.
Old 02-11-2018, 12:19 AM
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Gotcha, you have to know what your doing to do rear ends or you end up with a disaster. I have read many of your threads through the years, you know your stuff.
Old 02-11-2018, 08:08 AM
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Is the color Silver or Pewter ?
Old 02-11-2018, 12:23 PM
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Pewter, your right the 3.42s and the stall work perfect for me. I just need to finish tweaking the shift points and the lock up for my taste.


Last edited by Carguy8888; 02-11-2018 at 12:27 PM. Reason: add type
Old 02-19-2018, 02:43 PM
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FirstYrLS1Z,
I had the day off today so I called Quick Performance. I have a Yukon clutch style posi unit and I did buy the master bearing kit. It is not an Auburn but since it has clutches I should change the fluid? I feel better at least knowing what I have now. Thank you.
Old 02-19-2018, 03:29 PM
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No,not as important as changing the fluid for an Auburn.
Auburn is a metal-to metal clutch,that one is spring pressurized plates-metal plates to non metal plates.
How many miles on it since the work was done ?
Old 02-19-2018, 03:47 PM
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Less than 1000 miles.
Old 02-19-2018, 04:10 PM
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If there's no leaks so that the fluid that was put in it is maintained,next year.
That design is similar to the Eaton positraction that was used in many cars from the factory and how many of those ever had the fluid changed ? I doubt 1 percent.
Only reason you'd be changing it would be to get the clutch's break in particles out and since the carrier/positraction was replaced(even though it's running quiet),the gear mesh does not perfectly match the previous mesh and that'll produce a new wear pattern which'll dump metal into the fluid. But not enough to worry about.

Last edited by FirstYrLS1Z; 02-19-2018 at 04:17 PM.
Old 02-19-2018, 04:13 PM
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Sounds good to me, the guy at quick said it was just like an Eaton too. Thanks for your great questions and knowledge.



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