I was going to break down and take my car to Jiffy Lube tomorrow to get the diff fluid changed. Normally I do all the maintenance, but just don't feel like dealing with the mess.They say that their fluid contains a posi additive in it already. Should I still get the GM posi additive and have them put it in? Will having both hurt anything? Will their included additive be ok? I have an 89 IROC with a Borg-Warner posi rearend. thanks...

 

i changed mine, really wasn't that hard, and i put in mobil 1 synthetic, and didn't put any posi lube, and it hasn't had a problem or noise yet. But i also don't think i have the Borg-Warner rear end, but if they say it has it, i wouldn't worry, u could always bring it back and yell at em.

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

[This message has been edited by breathment (edited September 07, 2001).]

 

JiffyLube uses straight-up GL-5 for everything, even if it says right on the tag to NOT use GL-5. I used to work there, and that's one of the reasons why I don't anymore.

When servicing a rear diff, they use a pump and a hose to suck out all of the fluid through the fill hole as best they can. Usually though people are lazy, and don't try to get all of it out. That or they don't even try. Then they hook up their GL5 gun and squirt it in there until it's spilling out, and seal it up.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

for a clutch type posi i'd use gm posi additive reguardless of what the gear lube says. i use mobil 1 gear lube with the gm additive.

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

Looks like Ed and I have some of the same habits...

The limited-slip additive contains an extreme pressure lubricant to save teh clutch cones from wearing to nothing when cornering. Even with synthetic gear lubes, it is recommended.

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Later,
Vader
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"Click - Click - BOOM!"
Adobe Acrobat Reader

 

Vader, I'll have to disagree with you on this one.

First, the additive is a friction modifier, not an extreme pressure additive. All GL-5's have the EP additive, a sulfur compound that forms an oxide film from the heat generated as the fluid is squeezed and rubbed between the hypoid gear teeth. As the film is formed, less heat is produced, film production is reduced, etc., until the film wears down and more sulfur is converted from the lube, and so the cycle goes until all the sulfur is used up. The EP additive is what gives gear lubes their distinctive odor.

The friction modifier acts on the posi clutches, and is the same thing that is added in Dextron ATF for smooth shifts. Synthetics tend to do a better job on the friction parts so they don't cause chatter, but the additive can still be needed in some cases. Often, the residual modifier from the drained fluid is adequate to do the job.

AMSOIL absolutely guarantees you don't need the friction modifier additive when you use their Series 2000 75W90 gear lube. I seriously doubt Jiffy Lube uses AMSOIL unless you ask for it or bring it in with you. I have never heard of any other brand that puts the modifier in, but there are still a couple of things I haven't learned yet.

BTW, the additive is not needed for locker-type units. No clutches.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

I agree with five7. Also, I would just do it yourself. I don't think it's any messier than changing the oil and filter. Pull the cover and drain it so you can clean the crud that deposits sometimes in the bottom of the diff.

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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, currant red metallic paint. Lots of other stuff...
82camaro

 

allright, you've shamed me into doing it myself. my car thanks you....

 

ya, Jiffy Lube doesn't deserve anyone's business, at least not the ones around here.

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

 

What about the zexel take off? whats the best fluid for it?

 

AMSOIL Series 2000 75W90. Although it works perfectly in clutch posi's, it also does the job with lockers. I have it in both my Camaro (stock GM limited slip) and '57 (PowerTrax locker).

The synthetic base will lubricate the gears and bearings better, reducing wear and heat, and will also withstand the heat that is generated better so it lasts longer. And, it is thinner at cold temperatures to boot, so it flows more easily when you first start moving.

[This message has been edited by five7kid (edited September 09, 2001).]

 

The zexel torsen takeoff is a locker?