Allright, I have a 1991 GTA w/ a 350. All GTAs came with WS6. And all WS6 supposedly had a posi rear.

I know I have 3:23s. But, when I floor the car, I only spin one wheel. Therefore, I'm guessing my posi is worn.

My question is... get it fixed, or get a new posi? I dont think a locker is for me, becasue I want my car to handle very well. I was thinking of going with a posi that constantly shifts the power to wheel that has traction. Supposedly this is great for going around corners. However, how does that handle in a straight line?

Thanks,
Bill

 

Limited slip = posi

Same thing, different spelling

I wouldn't worry too much about all the "WS6". Nobody cared about that until they started badging cars with it. In any case, it's a suspension option package, not a drive train option. The RPO for posi is G80. Your car I don't think necessarily had that.

Works fine in a straight line.

I'd suggest the high-perf Eaton. That's the one I have, I like it alot.

 

I know they're the same, I was using the terms interchangeably

 

I WOULD ALSO GO WITH THE HIGH PERF. EATON I HAVE IT AND LIKE IT VERY MUCH!

 

Is there a website with some info on this product? Where's the cheapest place to order from?

Does the Eaton lock both wheels up, or does it switch the traction from one wheel to another depending on which has traction? I was considering a posi of this type, but I'm not dead set on it.

 

Might want to try spending $20 for new new fluid and GM posi additive to see if maybe it was serviced and no additive was put in.

Could be all it is.

U would have to dissassemble it to investigate otherwise.

Personal preference on limited slips is leaning to Auburn for me. I think they feel "better" on the street and its why I elected to use it in my Formula.

Either way if u said no to Auburn than I would tell u Eaton. :-)

I've seen everything break a minimim of once lol

later
Jeremy

 

I had the fluid replaced just when I bought it. Maybe that is it. What is posi additive? How does not adding it make my posi not work?

Thanks!
Bill

 

without the additive most factory posi tend to slip. The clutches can't grab.
If you go aftermarket, one of the biggest factors would be whether its a 10-bolt or a 9-bolt. If it's a ten, you're good to go with many manufacturers. If it's a 9....well, start hunting. -
- if it's a 10-bolt and you go new, I highly recommend the true-trac. IK beat the hell outta mine and love it.

 

Is the true-trac the kind of posi that constantly switches the power between the two rear wheels? How is the true-trac around corners?

What kind of rear differential fluid and addative would you guys reccomend? I like using synthetic fluids when possible, unless the non-sythetic is better for the application. Where can I buy the stuff?

Thanks!
Bill

 

Verify by dropping the cover before you get too carried away.

JamesC

 

True-trac = limited slip

Just another spelling employed by a different mfr

All that a typical stock posi is, is a set of clutches (whether plates or cones) that connect the axles to the carrier. In effect connecting the axles to each other. Which means, it requires some significant amount of torque to force the wheels to turn at different speeds. Which means, that even if one wheel has no traction whatsoever, there can still be that much applied to the other wheel. Typical stock posi breakaway torque is in the 35-60 ft-lb range depending on the model of rear. Doesn't sound like much, but it sure beats 0 ft-lbs.

I don't know of any differential that "switches" power around. They're much more crude than any of that. They're very passive, nothing active about them.

Generally a stock posi, or any other clutch type, will have the OPPOSITE problem to slipping, without the additive. It will chatter and groan and carry on like something is broken in the rear when going around corners. In fact I have a 8.5" (in another car) that's doing that right now. It's the stock posi out of a 84 Buick Lesabre, but that's not what it's in. I need to get motivated and slap a bottle of additive off in it .... again.

JamesC is right, in fact that was exactly my point; just getting all satisfied about your car having WS6, whatever that happened to mean in your particular year, doesn't guarantee that you even have a posi (of ANY spelling). Doesn't have ANYTHING AT ALL to do with posi.

You should ALWAYS pop the cover and look at what's in your rear end, before buying parts. And that goes for your car's rear end too.

 

Sorry for not keeping up with this thread. I got sidetracked with the Air Force and college classes.

I finally got around to checking out my RPO codes, and I do have G80, meaning I should have a posi.

So do you guys think that it could be a lack of posi additive in the fluid that's causing my problems?

I think this may be the problem, since I had the fluid changed (at a dealer ) as soon as I got the car. And, I paid through the nose for it.

Should I try tackling this job myself, or should I get my mechanic to do it?

Also, can you guys reccomend a fluid and an additive? I love synthetic oil (Mobil 1 and Royal Purple for me), but will synthetic posi fluid and addative make a difference?

Thanks again,
Bill

P.S. Does anyone know the RPO codes for a 9 bolt and a 10 bolt rear?

 

Mobil 1 and GM additive. Crawl under the car and count the bolts.

JamesC

 

Thanks James C! Do I use Mobil 1 motor oil or do they have a special posi fluid? In either case, what weight do I need?

Any ideas where I can pick this stuff up? Pep Boys should have mobil 1 oil, not sure about posi fluid tho. I guess I should go to a dealer for the GM posi addative?

Thanks again!
Bill

 

Mobil 1 75w-90 synthetic gear lube along with GM posi additive. Try AutoZone and your GM dealership.

JamesC

 

I noticed you keep mentioning that you want a posi that constantly switches back and forth between axles for the best traction. I'm surprised nobody has mentioned the zexel-torsen units that came in the 98 and newer f-bodies. That's precisely what these units do. There's no clutch packs in them, just gears that constantly bias traction between the two axles. SLP used to sell them for $99 a piece when they were taken out to upgrade to the auburn pro series units. Although you can't buy them from SLP anymore, I still see them all over on ebay for an average price of about $150. Also, if you still have your stock 91 ten bolt rear, you should already have 28 spline axles, which is what the zexel-torsen units require. Just figured I'd mention this option to you in addition to the eaton and auburn units.

 

GM says I need 80w90, should I use that or the 75w90.

I picked up the GM limited slip additave today. But, I can't find Mobil one or Royal Purple in 80w90 at any of the local shops. One GM dealer does have the 75w90 in the Mobil 1 tho.

How much of this stuff do I need?

Thanks!
Bill

P.S. Pat, can I do burn outs with the Zexel-Torsen unit?

 

I went Eaton as opposed to Auburn(cone type)-Eaton is rebuildable, but Auburn may have a rebuildable unit now.

 

I just ordered an Auburn High Performance posi with some 3.42 gears.. I have the same exact symptoms as you (except i've already pulled the cover, verified the differential and tried new fluid)... Hopefully the new posi and the 3.23->3.42 gear swap will help my poor 60' times at the track...

 

If your posi is not working at all, changing the fluid will probably not help you much. It might help it a little bit, but if the clutches are shot there is nothing you can do to 'fix' it except replace it.

You said you were interested in a good differential for handling. The best one out there right now is the Torsen T2R. That is the differential most of the guys winning national championships in SCCA Solo racing are using.

Check out =http://www.stranoparts.com. I think they are in the $500 range. From what everybody that owns one says, they are WELL worth it. BTW, Sam Strano has won several national championships running f-bodies, so he knows what works and what doesn't when it comes to making an f-body go around corners.

 

a torsion style limited slip dose not switch back and fourth, it has idler gears and worm gears in it, and it uses the fact that a worm Gae can turn a regular gear but not vise-versa, it gives power to both wheels, but allows the wheels to move faster than the carrier but not slower, so you get full torque to both wheels, Porsche has been using them for years, but American car company's stayed away from them due to the fact that they tend to be weaker then clutch or cone type LSD's, I think what he's trying to refer to in the switching back and fourth could be the old "Detroit Locker" ratcheting type, they work good, but when you go around a corner all you hear is click, click, click. just my