Ryan89IROC

I have the 9 bolt rear end and I checked the axle code and it is a posi rear end. However, when I did a burnout, I only found one tire mark. I did another one and sure enough, fifteen yards of rubber, but only one strip. Does any one know what's wrong? thanks for the help.

Omega

iTrader: (1)

Chances are the posi is shot. Either the cones are worn or the clutches are shot. I am not very familiar with 9 bolt. All i know is that they are expensive to fix. Take it to a shop and make them have a look.

------------------

• 89 Formula 305 WS6
  SFC's,
  LCA's,
  Air foil
  Flowmaster cat back
  Tranny Cooler
  A/F Ratio Meter
  Trans Temp (not a mod but it sure spurs interest)
• 90 Eagle Talon 2.0
  (winter beater)
  Mods? HA! its a rice burner!

Ryan89IROC

It seems strange though that it doesn't make any strange noises or anything, even in hard use. Does anyone have any suggestions as to the best ways to fix this?

Ed Maher

9 bolts are a rebuildable cone style posi...not sure of where you get the rebuild kits, but they do exist. Someone will chime in hopefully.
As to why the no funny noises. Think of it this way. Your rear (like all factory rears) is a differential. Which means the wheels can move at different speeds. All your posi does is use the cones as clutches, so that when one wheel starts to spin faster than the other one, the friction of the clutches pulls the other wheel closer to the first wheels speed. Or, the spinning wheel is slowed down by the clutches. Either way, once the clutches are worn, there is less friction, thus less ability to keep the wheels close in speed. You don't hear any funny noises, because nothing is broken. It's just worn out. and doesn't work as well. I'll bet you can still leave two tracks in some dirt/gravel.

If the rebuild kit proves hard to find or too expensive, here's what you do. Change the fluid but DON'T put any posi additive in it. Posi additive is actually an extra lubricant that helps the posi clucthes slip more smoothly so your rear doesn't make noise in tight turns. Since your posi is dying, you need to maintain all the friction you can, thus run no additive. I know this works on 10 bolts, why not 9 bolts.
...ed

Ryan89IROC

Hey, thanks for the help. I would like to keep my nine bolt so I would appreciate the info if someone knows where to get parts for it. Otherwise, maybe someone could tell me what I would expect to pay for a fourth gen rear. Thanks

The ODB

Ed,
could you please double check your info for my sake? This could be embarrassing, but I'm almost 35 and always been told that the posi additive (friction modifier) was to actually increase friction to the clutches. The gear oil should provide normal lubrication, but needs the friction additive for a posi with clutches. People have also put this in their trannies (not me).

I have not run clutches in a rearend in a long time, so I use sythetics and friction reducing additives (moly, ptfe, etc) in my rears.

I still want to know though and wonder if I have been misled in the past. I never actually tested the posi additive myself because the story I heard seemed believable.

thanks,
ODB

Fastcamaro87

the nine bolt posi unit can be shimmed, i beleive there is an article in the tech section,

------------------
87 IROC-z 305 TPI 5spd Borg warner 9-bolt 3.45 posi 4 wheel disc,8.8 Accel wires , bosch platinum +4 plugs,gutted air box,k&n oil filter,synthetic oil 10w30

82z

Does the 9 bolt posi unit contain any clutches? I don't think it does. What would you do to rebuild it? As far as I know the cones directly contact the case.

------------------
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

Ryan89IROC

What is involved in rebuilding the rear? I have average mechanical ability, Ive opened up manual trannies and that kind of stuff but other than changing the oil have never messed with diffs. Is it something I may be able to do? Where do you get parts. Thanks

Ed Maher

ODB, i honestly don't know where i first heard that, i picked up that tidbit along time ago.
Anecdotal evidence that posi additive is a friction enhancer would go like this...notice that when someone is complaining of the rear making noise adding posi lube helps...to me that means the noises were the clutches slipping irregularly, the additive helps them slip smoothly
My other piece of anecdotal evidence is this...synthetic rear lube users are told they don't need the posi additive anymore. I don't think synthetic rear juice has MORE friction than it's dino counterpart.

I could be wrong on this though, as i said, the fact has been in my head for a long time, kept alive by those examples above. If i get a chance later i'll try to look it up to be sure though.
...ed

The ODB

Thanks Ed,
Any new info yet?
anybody else know for sure?

I've never heard about NOT using the modifier with synthetic. This confuses things even more.
Obviously I've been kept out of the loop on the gear lube tech.

GMTech

Friction Modifier MAKES the gear oil SLICKER. Thats why people who don't put it in get "chatter" when they go around corners.

In a posi, there are large springs that keep the clutches pre-loaded. So really, at all times, the posi is "applied". When you go around a corner, as you know, one wheel wants to turn faster than the other. When this occurs, the pre-loaded clutches try to keep the wheels at the same speed. Of course the car making the turn over powers the tiny clutches, and they "chatter" as they slip. So the friction modifer allows the clutches to slip without A) chattering and B) burning up.

But when you lay on it in a straight line, the pinion gears (not to be confused with "the pinion gear) try to push the spider gears away from each other, and further compress the pre-loaded clutches and that is when the Posi fully engages.

Now that you have completed Posi 101, please stay tuned for the post-test and certificates will be recieved in 6-8 weeks.

------------------
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,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

[This message has been edited by GMTech (edited March 03, 2001).]

The ODB

Gmtech,
thank you.
next question is what is in the friction modifier? is it only good for clutches or does it reduce friction of metal-to-metal as well. Would you put the stuff in a locking or spooled rearend?

thanks again.
ODB

The ODB

btt

five7kid

iTrader: (14)

It's primarily for the clutches. For the metal-to-metal, you have two conditions: The bearings and the hypoid gears.

For the gears, you need the "extreme pressure" additive, which is a sulfer compound - that's what gives gear lube its distinctive odor. When the gears do their mating ritual, heat is generated that converts the sulfer to an oxide, which forms a protective coating on the gears. As the coating wears, heat is again generated, more sulfur is oxidized & plated on the gears, etc.

For the bearings, the base lube is adequate (i.e., heat not high enough to form the sulfur oxide), but a synthetic base will protect a little better and provide less resistance.

I couldn't say about synthetics in general, but what AMSOIL has said in the past about the posi additive is; try without it, add it if needed. With their 2000-series lube, they flat-out say you don't need it. I didn't have any trouble with mine when I switched it over with the newer stuff without any additive.

As for lockers, my PowerTrax instructions didn't say anything about the posi additive whatsoever. I haven't installed it yet, but I'll be using the AMSOIL 2000 anyway. Spools wouldn't benefit from it - the EP that's already in the lube is what you need there.

------------------
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 (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
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 & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.