The posi in my 88 IROC started making these horrible grinding noises a few days back so i thought it was time for a fluid change. I drained out all the old fluid (didn't look bad at all, no metal particles except for the usual powdery stuff on the magnet) and replaced it with new 80W-90 gear oil and added Trans-X Limited slip additive. It worked like a charm the first day - no more noises. Then when I drove it again today the noise was worse than it has ever been. It was making squealing sounds, grinding sounds, all kinds of noises basicaly, even on the slightest turns. Now the noise is so bad that I can actually feel vibrations from the differential trying the prevent the wheels from turning at different speeds. In fact, it's almost like a Detroit Locker now. It just hates turns.

I used to be able to break the inside wheel loose on turns if it accelerated hard. Now the rear end stays planted until the power breaks both rear wheels free at the same time. It seems like it isn't 'differentiating'. I know the added traction is a good thing but the noises are really worrying me. I don't want this thing suddenly distintegrating one day and destroying the entire rear end.

Could it be that it is actually a locker and not a posi? When I removed the cover I could see the ring and the pinion gears, the differential gears and some springs attached to the differential carrier/cage. Is that what a posi is supposed to look like?

------------------
'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Ported plenum
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.

 

Sounds like your posi is worn out. A locker clicks when turning.

------------------
82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

See the tech articles at Randy's site here... Diagnosing noise 1 and 2. Good luck.

http://www.randysringandpinion.com/GearTalk.html

------------------
'89 Formula - Thunderchicken - 355 Vette L98/T-5/3.45 9-bolt/black/t-tops - the fun car!
'90 GTA - The GTA - 5.0 LB9/TH700/3.27 9-bolt/black/t-tops/tan leather - the cruiser.

 

Brian,

According to the article, it seems like the clutches are worn out and instead of engaging smoothly they are grinding in there. It sounds exactly like the article describes it - like a sledgehammer pounding away on the rear end. It also gets worse as oil temperature rises.

Am I risking completely blowing out the rear diff by driving it or will the posi continue to wear out until it becomes a one legger? I don't want to end up grenading the spider gears and get stranded on the side of the highway.

Is it possible to change out only the ring gear and carrier cage and leave the pinion in there? I know a simple swap wouldn't be beyond my scope of mechanical abilities but changing out the entire rear end would be a real pain. Also, how much does a complete thirdgen posi rear end cost? I mean just a ballpark figure.

------------------
'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Ported plenum
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.

[This message has been edited by 88irocz28 (edited June 04, 2001).]

 

lemme be the first person to vouch for randy's ring and pinion... they're local for me and they KNOW THEIR SHYT!!! ... they really helped me get details for my new rearend worked out

 

Can the existing posi be repaired by opening it up and replacing the worn out clutches, etc? I really don't want to go through the hassle and expense of getting a new rear end now.

To be honest, the posi was making a lot less noise before I changed the fluid. It seems like the paricles of the worn out clutches were still afloat in the gear oil and lubricating the whole thing properly. The new gear oil has made things a lot worse. Since I still have the old oil, I'm seriously contemplating filtering it to remove any debris that may have fallen in and refilling the diff with it. At least the diff will last until I can afford a new one. It is a pretty hare brained idea but i can't think of anything better right now. What do you guys think?

------------------
'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Ported plenum
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.

 

To be honest, yeah, you could probably rebuild that posi with a kit from one of the many rear end specialists places - Randys, DTS, DTD, Tom's... lots of places.
Here's the rub, If you got a 10 bolt with 2.73 gears on a posi with 26 spline axles - or at least that's the way it probably came from the factory. Why bother???? You'd probably have to have some help getting them set up correctly, then ya still got 2.73's. It's also a series 2 carrier and really you need a series 3 carrier to bolt on some gears.
You might have the optional 3.23 gears if you got G92 (rear disks????)... I dunno for sure - your car - not mine. That's a series 3 carrier already.

Go junkyard hunting this weekend or next and see if you can come up with something better like a 3.23 or 3.42 posi out of a 90-92 car. There's some 9 bolts on the classifieds if you wanna go that way too.
That gets ya 28 spline axles and a big F'ing smile on your face when you get it together and blow somebody's doors off.
Swapping the whole rear isn't as bad as you think... as compared with paying for gear setup. Just an idea. You need to swap speedo gears too.
A decent used rear can probably be had for $300 ish... depending on what you get.



------------------
'89 Formula - Thunderchicken - 355 Vette L98/T-5/3.45 9-bolt/black/t-tops - the fun car!
'90 GTA - The GTA - 5.0 LB9/TH700/3.27 9-bolt/black/t-tops/tan leather - the cruiser.

 

I spoke to a bunch of local shops about what makeshift repair i can make to the rear end to let it last until I can afford a new one. All the money hungry bastards are absolutely sure nothing can be done other than rebuild the diff. No duh! I'm talking about a 'makeshift' repair, like some kind of additive or something that will give me a few more weeks. One shop went so far as to tell me that I have broken bearings inside. I felt like slapping the dumba$$ technician upside the head. I know waht broken bearings sound like. Been around cars to long not to know.

Anyway, time to finish the rant. I think I may have found a way to save the posi for a bit longer. Lucas auto transmission additive. The stuff did wonders for my tranny, and it claims to build a polymetric film of the cltuches/bands lengthening their life for a bit longer. I thought if it worked in the transmission, it definitely worth a shot in the diff, especially since I have nothing to lose. So far it seems to be working at least a little bit. The only time now the diff makes noise it during full lock slow turns like in a parking lot. This is with only one bottle added to the regular diff oil. I might drain out some add another bottle in there. What do you guys think? Should I, or will it cause lubrication problems since it's so thick?

------------------
'88 IROC 305 TPI
Crappy 700R4 slushbox
Gutted airboxes
180 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel (gotta luv it)
Ram-air setup coming soon
Flowmaster muffler (puke)
Taylor SpiroPro wires
Accel cap and rotor
Ported plenum
Kills: '94 Z28, Olds Aurora V8, bunch of Mustangs, T-birds, ricers, and others who assumed a 12 year-old car would be too slow.