well i finally got my 88 gta running pretty good until now, i changed the rear end fluid the other day and after i drove it about 50 or so miles my posi stopped working. now only the right side spins and the left only spins sometimes. and yes i do have a true posi, its the auburn according to the dealer. now i didnt add the additive i didnt know you had to, i used castrol 80-90 dino in it. aside from the posi not working there has been this whining coming from the rearend when i get above 10 mph, accel or decel dosent make it louder only speed does. any ideas? i am hoping i dont have to rebuild the rearend.....

 

Go to the dealership and purchase GM's additive (p/n 1052358), throw it in and see what happens. You have nothing to lose.

JamesC

 

Agreed, if the gear whining doesn't go away its probably about time to tear into it.

 

The Auburn wears out and stops working. Yours might have just got to the point where it isn't going to work anymore. If this is the case then no amount of oil additive or anything else will fix it. You will have to replace it. The Auburn can not be rebuilt. When they wear out they are scrap metal. If you have 3.23 to 3.73 gears then I recommend replacing the Auburn with a new Eaton. The Eaton will last a lot longer and it can be rebuilt if it ever does wear out. It also won't fill the rear end with powdered metal like the Auburn does.

 

ok i put the additive in there and no difference really, its still roaring loudly. there was a tag on the hogs head and it said 3.27 gear ratio. i looked up the eaton rear ends and wow they are expensive...is their any other alternative thats cheaper and would allow me to change it to 3.73? i bought the car for $500 with 237k on it and its my daily driver so i dont need any thing too radical....

 

If you have 3.27 gears then you have the Borg Warner 9 bolt rear end, not the 10 bolt. The only differential available for the 9 bolt is the Borg Warner. This is a cone type differential. When it wears out you have to do some machine work to restore it. There are several threads on here that explain how to fix it.

 

You can however swap in a complete rear end from another car. Any rear from 1982 - 2002 F Body will swap right in - 1993 and later are slightly longer axles and thus slightly wider rears.

I bought my 2002 LS1 rear for $200 - has 3.42 gears and nice big LS1 rear disk brakes. Tires stick out a tad further on each side, but the swap is easy (takes maybe 2 hours).

Swapping the entire rear would probably be cheapest - and if you aren't a serious racer or street racer, someone would probably buy the 9bolt rear from you and cut your expense for a new used rear in half. Hunt Craigslist or the local boneyards for wrecked F bodies.

 

Yeah, you're really in a pickle when the posi goes south on a 9 bolt, unless you can find someone to machine the posi cones and then shim them back up properly. As mentioned above, there's a good tech article on here that explains how to go about it. If all of that sounds like too much of a PITA then your best option would be to replace it with a 3rd or 4th gen 10 bolt rear. You can still buy all the bearings and seals for rebuilding the 9 bolt, but NOBODY sells a new, aftermarket posi unit for them. Every once in a while I'll see a NOS 9 bolt posi carrier for sale, and the price for one makes the 10 bolt Eaton unit look like flea market prices in comparison! Oh yeah, almost forgot, if you do decide to rebuild your 9 bolt, you actually can order a new 3.70/3.73 ratio ring and pinion for it. In fact, that's the only ratio you can buy new aftermarket for them, and it fits on your 3.27 carrier. When going to most gear companys' websites, the 9 bolts are listed as "borg-warner 7.75 inch rear", so that's the category to look under for ring/pinion sets, bearings, seals, etc.

 

ok i found a rearend local for $150, it came out of a 1996 formula. guy says it has 3.42 gears and is a posi, came out of a 6 speed car. mine is a 9 bolt rear, will it bolt right up?

 

Yes, but you'll need to consider the combination valve, parking brake cables, and speedo drive and/or driven gears (if you want the speedo to read correctly).

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

he has a 4 wheel disc car,so you dont need the p.valve and you get the speedo gear from the donor car.the park brake cables are also no big deal.

i did this on my car already

 

the additive helps with chattering around corners.friction modifier.

not with noise or a worn out posi

 

get it ! thats cheap.

it will be wider.

look at my pics to see.

its in the firebird.

 

Though he has a disc brake combination valve, the one he needs for best brake performance is the first-design 1LE valve (the bias increases from drum to standard disc to the so-called 1LE). He'll also need the first-design parking brake cables, which don't require modification--if you used the cables from your LT1 or LS1 swap, please provide more info. And, of course, he may or may not be able to retrieve the speedo gears, depending on whether the trans is still in the car.

JamesC

 

so where would i buy this valve? and yea im getting the speedo gear as well

 

http://www.flynbye.com/catalog/i40.html

JamesC

 

i was looking around on the faq board and it said i have to use 4th gen wheels with my new rearend, is this correct

 

3rd gen wheels will bolt right up. IIRC, using 3rd gen wheels make them stick out a bit further due to a different backspacing, or offset. Or maybe it's the other way, and the 4th gen wheels stick out further. But I'm pretty sure the 4th gen wheels tuck in a bit better from what I remember in posts on here. Either way, the 3rd gen wheels will bolt up and work.

 

3rd gen wheels stick out about 1 1/2 inches farther each side - the 4th gen axle is just over 3 inches longer total, thus the 3rd gen wheels stick out farther. 4th gen wheels tuck in under the fenders as they should, but ONLY in the rear - spacers HAVE to be used in the front if 4th gen wheels are used on the front of a 3rd gen, because the wheel backspacing is different and the 4th gen wheels will rub the tie rod ends on a 3rd gen car.

ALSO, the 15inch 3rd gen wheels will NOT fit over the LS1 brakes (1998 - 2002) - but 16inch 3rd gen wheels do fine. Keep in mind that also, the 3rd gen spare will not clear the LS1 rear brakes either, and another spare is needed.

This is with Camaro wheels anyway - I'm not sure on the 15 vs. 16 inch "bird wheels, or if "birds even had 15's on them.

 

Hey, good call! I totally forgot about the LS1 style brakes not clearing 15's. The 15's just BARELY clear my 89 style PBR's. And yeah, for the spare, he can just grab the spare from any 4th gen that came with 16" wheels. It works great and even fits down in the trunk where the original spare went. I have one of the original space-saver, collapsible spares that clear the PBR's, but it's all weather cracked when inflated, plus it's a PITA to have to inflate it anyways. So I grabbed the 4th gen spare out of the boneyard for cheap. It's already inflated and ready to use, and actually fits in the stowage spot, just barely, but it does fit in there.

 

can i use my third gen calipers and such?

 

To use the 82-88 Delco-Moraine calipers and standard rotors, you'd have to swap on an old 10-bolt backing plate, which requires axle removal (the 9-bolt has a different bolt pattern). Then, there'd be the issue of lines. The fourthgen rear would have flex lines to each caliper, the old style, a hard line to the driver's side, a flex line to the pass--and after all that, you'd have taken a step backward, IMO. If the fourthgen rear has backing plates, throw on the correct rotors and PBR's. Less hassle and better braking.

JamesC