I have the original window sticker for my 92 Formula. It has the L98, and on the sticker it says "performance axle ratio" but does not give the ratio. It's running a 3.23 right now, but this rear end needs to be rebuilt. Is the 3.23 right for this? I'd think the 3.42 or 3.73 would kick a little harder. I have the build sheet here too with the rpo's, but don't see anything about axle ratio.

 

Optional rear gear RPO is G92.
You should also have an RPO for the exact gear ratio on the SPID sticker.
So a car with standard 3.23 but equipped with 3.73 would have GT4 and G92.

As far as I know, 3.23 was the optional rear gear for that year / engine / trans.

And I don't recall the old school build sheets (which had rear gear info) to be placed in 1991 models, as SPID stickers were implemented years before. So you may have a "trim sheet."

 

That's part of the problem. Window sticker and build sheet, but no door or console stickers. Have no idea what happened to them. Also, don't see anything with G92 on it. What I have says "schedule/job" on it, and has the vin and job number that matches what's on the car. I've called that a build sheet, but am I mistaken? I found it inside the door panel.

 

You may be right about the trim sheet. Mine is a 92 though, not a 91. It does say "trim" near the top. This>>>>

 

On what sticker does it say perf. ratio?

You bought it used. It could have 3.23 or it could have been swapped.
You're rebuilding and have the opportunity to change it. If it's staying TPI and auto, go for 3.42 or (yes there are aftermarket gears in) 3.55. If you're going wilder or changing to manual, consider something a bit higher.

 

Says it on the window sticker, it just doesn't give what exact ratio. I found that in the rear glove box, which was borderline miraculous. The axle situation is a bit more complex. The original axle was a 3.23, but is claimed to have been bent slightly, because a mechanic I know put in new bearings, and about 200 miles later it completely chewed them up. I got a used assy from Hawks that is a 3.23, and that is the one that needs to be rebuilt. It works ok for now, but whirrs a little. I think the mechanic was full of it, I don't see any bending in that housing, I think he just screwed it up and didn't want to admit it. He said it was out of square by 1.5-2", which is absurd, because looking down the tubes looks like a bulls eye. If it's bent, it's so minuscule that I doubt it would have caused the catastrophic failure we had in 200 miles. He also told me the car had been wrecked, and that it was 5/8" out of square, I wasn't buying what he said. I took it for a 4 wheel align, and the thrust angle was off by 13/1000 of a degree, which is totally normal for a 23 year old car. But that was a year ago when I knew almost nothing about rebuilding axles. I know a lot more now, and am about 90% sure I could do it myself. I'm only worried about pinion depth and working up enough force to pre load the pinion bearings. Needless to say, I'm not taking my car back to that guy for anything. I hate using mechanics period, and won't anymore unless it's just absolutely something that is way over my head, like rebuilding a tranny.

 

Did you check on the back of the spare tire cover for the sticker? I've seen it there on a few cars.


A 3.42 or 3.73 will make it feel a little quicker, and it will make the tires spin a little easier. I would use a Eaton Posi, Yukon Dura Grip or Power Trax Grip LS for the rebuild.


You need to check the axle splines on the replacement rear end. The '92 rear end would have had 28 spline axles, but the replacement rear end could have 28 or 26 spline axles.

 

The one that came on the car had 28 splines, and I still have the axles for that and they are in pretty good shape. I don't know the spline count on the replacement because I've not opened it up. It's probably 28. I don't have the carrier bearings, so it's tough to do a real straightness test on the original housing. If I knew the old housing was straight, i could do my rebuild in stages at my own pace without having to disable the car by having it stuck on jackstands. I could just do my rebuild and swap it out when ready!

But checking in the spare tire area for the sticker is a great idea. I've had that panel off and don't remember seeing it, but I might have overlooked. I'd love to have it so I could "remake" door and console stickers for originality.

 

Around 90 or 91 (IIRC) the RPO sticker went to the rear driverside locking compartment lid.
R6P was the rpo for the performance enhancement package and 3.23 is the gear for that.
A little more gear will make it more punchy around town but cost some mileage on the highway.
A good trans rebuild and converter will really wakeup that slushbox trans.

 

Ok, I'll check the rear locker too, hopefully it will be there. Trans rebuild is on the list too eventually. It's like a lot of things on these older cars, it works ok for now, but not exactly like it should either. I may just stick to 3.23 when I do the axle, and look for a little upgrade in the trans when I can afford to get to that. It may cost me in the 2 grand area to get these both done, can't swing it just yet.

 

Which bearings did the mechanic replace that were damaged in 200 miles?


A bent housing can cause problems with the axle bearings, but if those bearings are fine then I would suspect that this guy did something wrong and was looking for an excuse to cover himself.


If your housing looks straight when you sight through the tubes then it's probably fine. If the axles are still good where the bearings run on them then you can use them again, but inspect the bearing area for pits or grooves. If they are damaged then they need to be replaced.


If your gears were not damaged when the bearings went bad then you can use them again, but setting up used gears can be a pain. The contact pattern on used gears can be very hard to read.

 

I forget what the brand was, I got them at Autozone. Timken--or something like that. He replaced the axle bearings when he did the job, they are still in the housing. If they're bad, I don't know it. The old were pretty bad, but somehow the axles survived pretty well unscathed. No galling or pitting. He also replaced every other bearing on the axle, including carrier and pinion bearings. They were all brand new! The post mortem showed the pinion bearings were the ones that REALLY got chewed up! I mean, they were demolished, like they'd been run over by a truck. Before it blew up I noticed a chirping sound when I'd let off the gas and coast--pinion bearing! I told him and had him ride with me and he heard it, but told me he didn't think it was serious but to keep an eye on it and let him know if it got worse. It didn't get worse by degrees, it just went all at once. I also had him buy brand new gears from Summit I think it was. When the bearings went, he said it ruined the gears too, and that I believe because the carrier case has gear marks on it, probably from the pinion. The carrier is an Auburn that he said was now ruined. But, I have a rear end/trans expert that runs a shop near hear that looked at it and told me he thought it looked fine. I didn't know he did axles at that time, or I'd have taken it to him instead of this other hack. This guy with the shop has been in the business for over 40 years, used to build race cars, and he's one I definitely trust. Did a great job rebuilding my 4th gen tranny. So if I do a rebuild, I'm going with new gears also. That should make the setup a little easier. BTW, this hack I went to was told to use 3.23 gears, just like stock. After he got done, I kept getting passed on the hwy, people flipping me off and so on. I realized my speedo was off by about 5-7 mph. I asked him if he put a 3.23 in it like I asked him, and he said "I did a 3.42, I thought it'd make you a little quicker when you start off. Hahahahahaha". Nice, I could hardly control my rage, but I did. Autozone was nice enough to refund me for the bearings, and amazingly, this guy told me Summit refunded me for the gears. I'm not sure I believe him on that one. Could be he felt guilty enough to give me the money for them back without telling me because he knew he screwed up. Mostly, the only money I lost was in purchasing the used assy, (which I can later re-sell if my old housing is still sound), and the labor I paid him to put the new assy in, which I could have done if it wasn't on jack stands in his garage. He will never see another of my cars again. All of this is why I've studied axles since. Live and learn.....

 

A bent housing will not cause pinion bearings to go bad. Setting the correct preload on the pinion bearings is critical, and also often misunderstood. My guess is that he simply did it wrong and then tried to sell you the story about the housing being bad. I'd say that you have a perfectly good housing to rebuild.


I am not a fan of the Auburn. It's my opinion that they are junk. The other differentials that I listed are much better. Take a chance on your old Auburn if you want, but I would certainly replace it.


Summit brand gears are not the best choice. They are a economy gear that had some corners cut during the manufacturing process. I'd use a better quality gear, and one of the better installation kits too.

 

Yip, I'm not surprised to read any of what you said. That chirp when I lifted never did sound right, even I knew it was the sound of a bearing in distress. My guess is, he didn't get enough preload on the pinion. I may take my housing over to the trans shop and have that guy give it a once or two over. If he says it's ok, may look at using it again.

 

Here is the diff that came out of the "bent" housing. (Know it needs to be cleaned off, gonna do that asap tommorow) I always thought it was an Auburn. But I'm not so sure now. Don't see any nomenclature, but there is a stamp on the side "E228 12". Could that mean it's an Eaton? How can I tell?

 

Nope, that's an Auburn. See the gear marks in the case? That's were the pinion wasn't tight enough and when you let off the gas the pinion was being pulled in and contacting the case.

 

So the hack didn't pre load the bearings enough. Just as I thought....@&#%* I figured the pinion made those gouges, but didn't know exactly why. But what about this tells you it's an Auburn? My eye isn't trained well enough, and some of the Eatons looked like they had the same spring and clutch setup inside the case.....

 

The easiest way to tell is by the number of springs. The Eaton uses 4 and the Auburn uses 5. Also, the shape of the preload plates, and the end of the differential case is a cap that is screwed on with a pin retaining it. This is to allow the tapered holes to be machined into the inside of the case. The Eaton uses a 1 piece case with flat clutch plates.

 

Ok. Gotcha. Thx! So the main difference between an open diff and a posi--from a guts standpoint--is that spring and clutch plate setup that presses against the spider gears and transfers the torque equally to both opposing lateral gears? Then the top and bottom are idlers, correct?

 

Nope. You can put those springs in a standard differential and it won't do anything. You can take the springs out of a limited slip differential and it will still spin both tires. The difference is in the clutches. The Auburn uses a cone clutch on both sides and the Eaton, Dura Grip and Grip LS use clutch plates on both sides. This is what makes them work.

 

Yeah, I think I understand that better now. I looked up several things online after I posted that. Steel and friction plates similar to what's in an AT, steel locked to the case and friction to the gears. Then the preload springs & beveled gears help produce a separating thrust force that packs the friction plates against the case, allowing the gears to turn with the case and etc. Makes sense, actually pretty simple when you see it laid out. Thx again, you've been a big help! If you don't mind me pestering you with one more question? I've heard a lot of guys say Auburns are junk, what about an Auburn's gear and clutch pack setup is more likely to fail than other units you mentioned that use this particular setup? (I know other setups use worm gears and etc.) Is it because Auburns sometimes use a cone clutch instead of plates?

 

As far as I know all Auburns use cones. This is not the only differential that uses cones, but the Auburn can not be rebuilt when it wears out. The Borg Warner uses cones and can be rebuilt at least once. When the Auburn wears out it's scrap metal. In my years of building rear ends I've seen several new Auburn units fail completely within 9 months. These were abused with lots of burnouts, but I've seen Eaton units last for 40 years and still work fine. The Auburn also fills the rear end with powdered metal as it wears, which damages the bearings. You have to do a complete tear down of the rear end when replacing an Auburn to clean the metal out of the housing.

 

Yes! Success! Thx for the tip TTOP350. I guess I'd have stumbled across it myself sooner or later, but thx still. I've had this opened up before, and just never paid an attention to it til now.

 

GU5 is 3.23 gear and G80 is limited slip differential.

 

RP6

You chopped of the end, second line is J65 - 4 wheel disc brakes, but what is the next one? R6? My guess is A......

R6A was an option group discount & I suspect it related to the performance group items - Gears, Posi, Oil Cooler & Rear Disc. I looked at a car yesterday that didn't have G92 or RP6 on it but it did have R6A, all the other items & GU6 3:42 gears.

 

R-6-P

 

I'm blaming John's dyslexia.

What car is that SPID from? It shows G92 & 1LE as well? Is that from a Firehawk?

Also - the 1990 car I just looked at didn't have R6P either - so what years did that 1992 bulletin apply to?

 

Here you go. It was the morning sun, dark shadow on the corner.

 

You're right, I'm puzzled.

Never mind.

Nice options btw!

 

lol

Yes.

That sheet shows Jan 2nd but I'm fairly sure i've seen it on 91 cars. Soo G92 till 90 and after 91 R6P. (I think)

 

Once you figure out exactly what you will need give Tom a call. He is highly recommended by many members here and his prices are hard to beat.
He has a 28 Spline Eaton Posi. for $429.00
= http://www.tomsdifferentials.com/





Here's a link to my 10 Bolt Build if you want to look.
There might be something worth reading in there.

=
https://www.thirdgen.org/forums/transmissions-drivetrain/526958-10-bolt-upgrade-photos.html

 

Ok thx, will do! There's another rebuild thread on here too that shows the whole process step by step with pics. I have it saved in my favorites and have looked at it many times. There's not much about it I don't understand, I'm just worried about getting the pinion depth right, and working up enough force to preload the bearings. I don't have air tools of any kind. Right now it's mostly just a money thing, I'd start on it today if I had more cash on hand.

 

Will you send me the link to that thread please. Either here or a PM. Thank You,
Ron

 

No problem Ron, here you go......

https://www.thirdgen.org/forums/tran...axle-gear.html

 

Ron, that thread is in the FAQ about 10 bolts sticky.

 

Thank you for the link . Now I know .
Yes, I've been there once or twice and I'm always willing to learn.
I just happen to have a shop in my town that's one of the best rear end shops in CA. or any where really so I went with them.


Side note = Maybe I'm blind but I cant find where it mentions what Carrier he is using in that thread. I believe I know but want to be sure.

 

I'm torn between paying more money to someone else (and I have an excellent axle/trans shop a half mile from my house) and the challenge of doing it myself. I can see pros and cons both ways. Not sure what I will do.

 

I also love a challenge and my car has given me a few already but for me the differential is different. With the tools I'm pretty sure I could do it.
If I was just messing around with an old rear end in a beater I would give it a try.
But not my Camaro.

I went with a man with 20 years experience building rear ends for this one.
To much money invested.

 

Thought it was an Auburn at first, but not sure the more I look at it. It's got 5 springs and uses cones though, so at least that makes it look like an Auburn.

 

Hey, I can top that. My guy here in town has over 40 years doing this! Used to build race cars, and did a great job rebuilding the 700r4 in my 4th gen a couple years back. One thing I thought I might do is remove the axle, get it prepped, cleaned and so on, then let him do assembly/setup, then put it back on the car myself. That would save me a little labor, but still get me a good axle. That is, if he'd let me do that, and I don't know why he wouldn't, seems pretty reasonable. He's that rare mechanic that respects stubborn gear heads who like to do things themselves. Cars are like WAGS. If another guy has his hands on her, he better be a doctor, and it better be real serious!

 

Perfect...
If you going to have some one build it for you then you struck gold with him.
There are soooo many guys that are just trying to find anyone with decent experience and if they do there miles and miles away so we both got very lucky.

 

It is an Auburn.