I just replaced the fluid in the rear end of my Cherokee and used black silicone to seal the cover back up because Autozone gave me the wrong gasket of course. I am doing the same in my IROC. Neither had a gasket when I pulled the covers. Is that how the OEM does it or have these been apart before. Also will gear lube help if my posi is worn and sloppy? What weight gear lube do you guys recommend?

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350 Vortec, forged flat-tops, CompCams XE268, Edlebrock RPM, Holley 3310, TH350 w/Holeshot 2400, 3.23 posi, Heddman shorties, HEI

 

The rear axles come from the factory with a gasket. Use 80-90 gear oil and some of the GM friction modifier. You have a 10 bolt with an Auburn Posi? Don't look for improvements in your posi by changing fluid. You could try just gear oil w/ out the friction modifier and see if the posi bites more. If you have problems with chatter, you can add a little of the aditive until it goes away.
My Auburn posi got soft on me too. After taking it apart, I found that one of my side gears was cracked and both cones were scored severly. I have a Torsen now. I seen them at SLP for $100.

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87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Goal: 12.999

 

If you are really that poor, you could probably get away with sealer, but its a half-@ssed way of doing things when a gasket is available.

However, if you do use sealer, DO NOT use synthetic fluid. Synthetic gear lube dissolves RTV, even when cured.

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If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass,
SSM SFC, Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

I put synthetic lube in my diff. about 4 years ago. It doesn't leak. I never used a gasket, just the make a gasket RTV stuff.
I guess I don't call it half-@ssed when it works great/doesn't leak. How long does it take to dissolve the RTV?


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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

Synthetic disolves RTV? Really?

I've been using synthetic lubes for over 17 years, and RTV all along the way, without a single "disolved" RTV gasket failure. Although the silicone content in the oil will increase if you overuse the RTV, that happens with either petroleum or synthetic based lubes.

Keep the bead size down so that there isn't a big goober sticking in the lube bath and you'll be fine. A bigger problem with overuse is having the excess bead break off and get into the works, especially on engines where it can block the pickup screen on the oil pump. Wouldn't be as big of a deal on a diff, although some have drain-back holes that could become plugged.

FWIW, not all axles come from the factory with gaskets. RTV has been used by several of the OEMs for years.

I highly recommend AMSOIL 75W90 Series 2000 gear lube. It has the posi additive in it so you don't have to buy it separately, and the synthetic base is a much superior lubricant compared to refined petroleum. But, to answer your actual question, just changing the gear lube won't help a worn & sloppy posi. Wouldn't hurt it, but won't cure it. Could free up a sticky posi, but that's about it for "help".

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

Yeah, some diffs do come factory with RTV like some of the Dana Axles, but they don't come with synthetic. However they do make gaskets for them if you want to use synthetic, why the difference, I don't know, I didn't design them, thats just the way it is. As for the synthetic issue, I was only talking about rearends, not engine. And if you havn't had any problems, then maybe it is certain brands.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass,
SSM SFC, Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE