Guys,

I plan to be a gineau pig with my 9-bolt. Those of you with 9-bolts may benefit from this. Be patient and read on.

The posi is wearing out on my 9-bolt rear. 9-bolt parts are easy enough to find (www.9bolt.com), but can be expensive. Since I Solo II the car according to SCCA F-Stock rules, the car must have a 9-bolt rear to stay in the stock class. I also take the car to as many road racing course open track events that I can afford.

When the posi first started to fail (in November), I purchased some Red Line 75W90NS Gear Oil. Red Line markets this oil for "non-limited slip transaxles that recommend 90WT oil. Can be used is racing limited slip units to increase lockup and reduce wheel spin. Street driven rear-wheel drive cars should use regular 75W90 or 80W140".

This statement got me a little worried so I called Red Line. They basically said that they do not recommend this oil for street limited-slip units because it will greatly increase lockup and will wear it out quicker. I thought, "great - liquid locker"! I then realized that I may be without a posi pretty quick and be in a worse situation. So, I sat on the oil and weighed my options.

In the meantime, I talked to a few guys that race f-bodies more seriously than I do (and in one case a professional) and they confirmed that the oil does work and also confirmed that it will burn up the unit prematurely. No one could give a firm answer regarding how fast it would burn up. I still sat on the oil.

By dumb luck, another member at this site said that he was selling his 9-bolt with functioning posi. I just drove the Toledo to pick it up today. He said that he was looking for a deeper gear and could get a whole 10-bolt rear cheaper than the 9-bolt replacement parts. Seemed like a sensible reason and he said that the posi still worked, so I bought it.

I plan to put the Red Line Oil in my current rear this week. I will report back what the results are - i.e. is it really a "liquid locker"? After that, I will wait to see how long it takes to burn up the unit (my guess is sometime this summer). Once this happens, I will report the mileage I put on it and how many of the miles were Solo II, road race track and street.

This should assist some of you when you get to my stage with your rear ends.

Let me know if this interests any of you.

 

I am interested in all the 9-bolt info I can come accross. Definately let us know the results.

 

Have you tried shimming the posi. There is a tech article that on this site that tells how to shim the 9 bolts cone style posi if it is worn to make it work again. The article is here: https://www.thirdgen.org/newdesign/t...tservice.shtml

Check it out.

 

Yeah, I have considered shimming the cones. Officially, (according GM), the cones are unserviceable unlike clutch-type posi's. Even so, I have confirmed via an old IMSA pit crew member, that they 9-bolts in the 1980's in race trim were indeed severely shimmed at the race shops. This was done under the assumption that the rear would only need to last one or two races.

The second reason that I didn't do this is I am a lousy mechanic. Probably not a good reason, but I avoid things that I know I will screw up.

Finally, I checked with three gear shops about having this work done and they all told me to "hit the road". I can't find many rear end specialists willing to even work on the 9-bolts.

 

Yeah man let us know what happens. The best rearend GM ever built and we can't get parts and nobody will work on them. Well we can get parts but the price is outrageous.

 

As far as not being able to have it done I understand that, but I dont think that if you reshimed it so that it contacted like stock it would cause it to wear out increadibly fast. I think that they are shimmed in factory form(could be wrong) so I dont see why as long as you dont go overboard it would hurt. I believe in the tech article it tells how shim it for different kind of uses.

 

im fortunate to have the types of performance shops here in memphis that we do.
i took my formula to DJ's Racing and if it werent for having to go out and get some main cap bolts for the carrier the swap would have been done in 2 hrs and that was being casual bout it.

 

I shimmed mine, and it recommends to shim the unit in the FSM if you read it carefully. It gives the specs too for the shim thickness. I havn't auto-xed on it since I shimmed it, but we'll see this summer. It feels tighter, but the real test is auto-x.

I too argued with a rear end shop after I shimmed it myself. They don't know better. One guy I spoke to told me he's doing rears for 30 years, and they can't be shimmed.

It is a big job, and you need air tools, or forget about it. I also sell shims if anyone needs them, and I have all different sizes.

Definately change the oil and let us know what happens. I wish I changed my oil too before pulling the rear apart. My gear oil was original, and I think that was part of the problem.

Larry Burd

 

Larry -

What does "shim the unit in the FSM" refer to?

When I swap in the rear I bought over the weekend, I may end up shimming it when/if the posi begins to give me trouble.

 

read the manual. It tells you to shims the CONES if the clearances are loose. Basically the same procedure that is listed here, but it tells you the specs.

 

To follow on this -

I put the Red Line Oil (described above) in my rear end on Friday. I autocrossed the car yesterday. The first thing I noticed is a constant, relatively quiet hum from the rear end (it's hard to hear over the Dynomax cat-back, but it's there).

At the autocross, I left two, black stripes of the same density on my one dry run. In addition, it felt like it was hooking up much better on the exit of corners. (Just for comparative purposes, I consistently had better times that my dad's BSP Vette until the last heat. This has never happened before. Hehe.)

I am pleased. I now have a functioning posi.

This begs the question:
Since there are conflicting TSB's on whether or not the rear end should have the posi additive in there, and I know that the additive was put in about 6,000 miles ago, would my posi still have functioned if the additive had not put in previously?

 

in my 9 bolt, i am running moble 1 75w-90, i think, i will have to go check. no additive....workn posi

 

The additive is a friction modifier. So I would think all it does it reduce the friction in the posi unit, therefore reducing your posi action.

I have Pennzoil GL5 gear lube which says on the bottle suitable for limited slip rears. So it has some built in additive in there.

Yesterday my posi was working much better but not as tight as I thought it would be. And I shimmed mine. So maybe it is the gear lube????

I'm not screwing with it anymore this season anyway. I was running very decent yesterday, and I know I have another 2 seconds in the car. So after I wring every second out of it, then I will worry about the rear.

I'm getting into road racing anyway, and posi's don't matter for that

Larry

 

Hey Larry -

I'm going to the open track event at Watkins Glen on May 6th/7th.

Wanna go? If so, send me an e-mail and I'll send you the details. If you want to check it out, it's a NASA Northeast event (http://www.nasanortheast.net/) piggybacked onto a SCDA event (www.scda1.com).

 

watkins glen is a high speed track. you'll be flat out, maxed out on the back straight. Get yourself some serious brake pads like hawk black or hawk blues. otherwise you'll be in big time trouble after a few laps. and freshen the brake fluid.

I'm going up there on may 18th.

my car topped out at 110-115mph. I was redlined in 4th. Had to shift to 5th.

 

Hmmm... I thought it would be faster than that. I've been here a few times ( http://www.fastone.com/TMap99.pdf ) and heading into the braking zone for "The Kink", I'm sweeping past 125... I guess I'll find out.

 

I thought you run FS which means stock. my car doesn't have the top end like I thought. maybe cause I have 3:45 gears. you prolly have 3:27's. that may make the difference.

 

Actually, I have the 2.77 rear end. It sucks in autocross, but isn't bad for mileage or top speed. I really don't know how fast the car will run. I am hoping to find out at Watkins. One of my local autocrossers in a 4th gen said she bumped 140. She told me that you can basically stand on it at the exit of the Esses and not lift till the entry of the inner loop on the backstraight.

 

what is auto cross ? i am in IL where no speed shops or any of this stuff exist,

anyone ?

 

Autocross is another work for Solo II racing. It is a timed event (single car at a time - no wheel to wheel) where you run through a course of pylons shooting for the best time.

Try this: http://www.scca.org/
following the Solo II links any try this:

http://www.autocross.com and check out the drop-down box option on "getting started"

Finally, look here at what one of our local guysput together:

http://www.geocities.com/solo2civic/autocross_101.htm