The GM stuff?

 

yes or it will start growling at you! im serious it will make a growling sound! and you should try and change the whole gear oil every year to(keeps dirt out of the rear end) the gm stuff rules and it'll keep the posi differential lubricated fine. email me for any question on anything i'll tryand help if i can?!

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1989 firebird formula

Mods: converted from T.B.I. to a carburator 305 to a 350. Flowmater exhaust,hedman shortie hedders,202 heads,350 horse cam,bored.40 over, Edlebrock torker2 intake.

Future mods performer rpm air gap intake (polished) and 600 edlebrock carb, comp roller cam, and way better headsa 400 defintely in the works!

 

Why would you add a new bottle every year? First of all you would not be able to get it in if your diff is properly filled. You only need it when changing the fluid. I think that changing the gear oil yearly is overkill. I'd do it every 2 years or so. Oh yeah, make sure you don't get the posi additive on your clothes. I got some on my clothes in high school and the whole day after that people kept asking me what that smell was. Needless to say that sucked *** .

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82 z28 350cid, vortec heads, comp 262h cam, Holley 600cfm carb, 2in twice pipes, MSD ignition, turbo 350 trans, 3.73 posi, manly b&m megashifter

 

Use AMSOIL 75W90 Series 2000 gear lube and you'll never have to put in a bottle of posi additive. Plus, your gears will work more efficiently and the lube itself will last longer, as will the gears. What more could you ask for?

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited 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.

 

I just picked up my new timing chain tonite and the parts guy at a GM dealership told me that GM is no longer recommending using POSI additive. Anyone know about this or is that guy full of it?

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87 Z28 305 TPI, Auto, 2.73, Gutted air boxes, K & N fillters, SLP Airfoil, Dyno Max 3" cat back, Accel 8.8 mm spirals, Accel cap and rotor, Accel coil, rapid fires, and 170* Stat.
Best 15.414 @ 87.47.

 

Havent heard that one yet...

The 'POSI' additive is a friction modifier. Every manufacturer uses it in some shape or form on limited slip differentials. If the amsoil listed above doesnt require using it, then its already in there or the properties of the fluid are such that it acts the same as adding the friction modifier to a normal gear oil.

Just change the oil at the recommended interval, and use 4oz of your typical additive from wherever you want to get it. No need to be putting in extra posi additive every once in a while, it wont help if the oil is past its service life.

 

Thats news to me. The additive is VITAL to the longevity of the limited slip. Since the clutches are pre-loaded (partially applied) they need to slip some during cornering, hence the addition of "friction modifier". Since most products break down over time and loose effectiveness, limited slip differentials require service every 15,000 miles, which means new fluid, and additive.

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