Blue 90 RS

Need some help/input, please...

Found a rear on Craigslist. Guy says it's a 3.27 Posi Disc Brake rear end from a 1988 Pontiac Trans Am GTA. Says it has 150,000 miles on it. Only posted one photo (I've asked for additional pics). Supposed to come with all of the factory brake hardware as well. Tag on it in the pic (kinda blurry) appears to read:

P/N 10032270
Ratio 3.27

Does this sound legit? I'm far from knowledgeable on rears. I am, however, looking for basically exactly what he says this is. Said the only reason he pulled it was because he's upgrading; not supposed to be anything wrong with it. It was pulled from a running car last Saturday.

It will be going behind a stock 305, so I'm not worried about it being what it is. I'm most interested in the disc brake aspect. Conversions can be expensive. I'd also like to swap the gears to 3.42; is that possible with this rear? I'd like to change the gears, replace all the seals & bearings & put it in my car.

Assuming it's in good used condition, what would it possibly be worth?

Can anyone shed some light on this for me? I appreciate any/all input you're willing to share.

Thank you, guys!

sofakingdom

iTrader: (1)

Prolly a 9-bolt.

Prolly has the crappy Saginaw cast-iron calipers. Yuck. I'd rather have drums than those.

Not many gear choices available for it. I suggest you track those down and price em before pulling the trigger on the core. Avoid sticker shock and wasting money on a core that'll cost giga$$$ to do anything to.

I suggest you keep looking. Find a 4th gen rear, out of a LS1 car. FAR better brakes, already has the gears you want, prolly less miles and wear & tear. Only down side is, it's wider, so you'll need to run wheels with the 4th gen offset.

Blue 90 RS

You hit the nail on the head. 4th gen is wider, which I do not want. I'm trying to get to: 3.42, posi, disc brakes, 3rd gen width. Anybody got something close to that for sale? I'd even be OK with 3.23-ish gears.

Blue 90 RS

Another thought: can I get a 4th gen rear and swap everything onto my 3rd gen housing and axles?

big gear head

Why not just buy a new Eaton Posi, a new set of 3.42 gears and a good installation kit and put them in the rear end you have now? Swapping used gears into another housing is harder than setting up a new set of gears. You should already have the larger 28 spline axles. The disc brakes with the old cast iron calipers are not really an upgrade from the drum brakes.

Blue 90 RS

That doesn't give me disc brakes, though. I know they make kits, but they cost mucho $$$$.

gearheadotaku

iTrader: (1)

Yeah, sounds like a 9 bolt. It's not all bad if it's in good working order. There are way to add shims to the posi if its worn out instead of spending money on a rebuilt unit for a 10 bolt. Whats the price? 4th gen rear isn't wrong by any means. They have gotten cheaper and may be the way to go if you find a good one.

I have a 3.27 9 Bolt in my car. The 305 TBI likes it. Other gears are out there, but not worth the price. (3.45, 3.70, and maybe 3.90)

Night rider327

iTrader: (13)

10032270 = 1986 borg warner 9 bolt 3.27 Posi

No you can't just swap the 4th gen rear parts into your 3rd gen housing. The 4th gen uses 28 spline axles that are longer than the third gens. You could put the 4th gen carrier and gears into your third gen housing and then buy aftermarket axles to fit

If you look at anymore used rears take a wire brush with you and clean the bottom side of pass side axle tube a few inches out from the center.. It will have a code stamped into the tube.

Here's a list of the codes.

GM 7.5"-7.625" 10-Bolt Axle Codes
1982:
2JE 2.73 Std 2JG 3.08 Std 2JH 3.23 Std 2JJ 3.42 Std
2JR 3.42 Posi 2JW 2.73 Posi 2JX 2.93 Posi 2JY 3.08 Posi
2JZ 3.23 Posi 2KE 2.73 Std 2KF 2.93 Std 2KG 3.08 Std
2KH 3.23 Std 2PE 2.73 Std 2PW 2.73 Posi 2PX 2.93 Posi
2PY 3.08 Posi 2PZ 3.23 Posi
1983:
4JF 2.93 Std 4JG 3.08 Std 4JH 3.23 Std 4JJ 3.42 Std
4JK 3.73 Std 4JQ 3.73 Posi 4JR 3.42 Posi 4JX 2.93 Posi
4JY 3.08 Posi 4JZ 3.23 Posi 4KJ 3.42 Std 4KK 3.73 Posi
4PG 3.08 Std 4PQ 3.73 Posi 4PW 2.73 Posi 4PX 2.93 Posi
4PY 3.08 Posi 4PZ 3.23 Posi
1984:
4PW 2.73 Posi 6JG 3.08 Std 6JH 3.23 Std 6JJ 3.42 Std
6JK 3.73 Std 6JQ 3.73 Posi 6JR 3.42 Posi 6JY 3.08 Posi
6JZ 3.23 Posi 6KK 3.73 Std 6KY 3.08 Posi 6KZ 3.23 Posi
6PN 3.73 Posi 6PQ 3.73 Posi 6PR 3.42 Posi 6PY 3.08 Posi
6PZ 3.23 Posi
1985:
4PW 2.73 Posi 6JG 3.08 Std 6JH 3.23 Std 6JJ 3.42 Std
6JK 3.73 Std 6JQ 3.73 Posi 6JR 3.42 Posi 6JY 3.08 Posi
6JZ 3.23 Posi 6KK 3.73 Std 6KY 3.08 Posi 6KZ 3.23 Posi
6PN 3.73 Posi 6PQ 3.73 Posi 6PR 3.42 Posi 6PY 3.08 Posi
6PZ 3.23 Posi
1986:
2EA 2.77 Std 2EN 2.77 Posi 2ET 2.77 Posi 8JC 3.42 Std
8JD 3.73 Std 8KA 3.42 Std 8KB 3.73 Std 8XA 2.92 Std
8XB 3.08 Std 8XC 3.27 Std 8XF 3.70 Posi 8XN 2.92 Posi
8XO 3.08 Posi 8XP 3.27 Posi 8XQ 3.45 Posi 8XU 3.08 Posi
8XV 3.27 Posi 8XW 3.45 Posi 8XX 3.70 Posi 8XY 2.92 Posi
1987:
2HA 3.23 Std 2HL 3.42 Std 2HP 2.73 Std 2HR 3.42 Posi
2HQ 2.32 Posi 2HT 2.73 Posi 4HB 3.08 Posi 4HR 3.42 Posi
4HV 2.73 Posi 4HY 3.23 Posi
1988:
6HT 2.73 Posi 6HE 2.73 Posi 6HP 2.73 Std 6HB 3.08 Posi
6HF 3.08 Posi 6HK 3.08 Std 6HL 3.42 Std 6HQ 3.23 Posi
6HJ 3.23 Posi
1989:
6HT 2.73 Posi 6HE 2.73 Posi 6HP 2.73 Std 6HB 3.08 Posi
6HF 3.08 Posi 6HK 3.08 Std 6HL 3.42 Std 6HQ 3.23 Posi
6HJ 3.23 Posi

1990:
8HP 2.73 Std 8HT 2.73 Posi 8HE 2.73 Posi 8HK 3.08 Std
8HF 3.08 Posi 8HB 3.08 Posi 8HJ 3.23 Std 2PM 3.23 Posi
2PN 3.23 Posi 8HC 3.42 Std 2PN 3.42 Posi
1991:
8HP 2.73 Std 8HT 2.73 Posi 8HE 2.73 Posi 8HK 3.08 Std
8HF 3.08 Posi 8HB 3.08 Posi 8HJ 3.23 Std 2PM 3.23 Posi
2PN 3.23 Posi 8HC 3.42 Std 2PN 3.42 Posi
1992:
8HP 2.73 Std 8HT 2.73 Posi 8HE 2.73 Posi 8HK 3.08 Std
8HF 3.08 Posi 8HB 3.08 Posi 8HJ 3.23 Std 2PM 3.23 Posi
2PN 3.23 Posi 8HC 3.42 Std 2PN 3.42 Posi

Borg Warner 7.75" 9-Bolt Axle Codes
1985:
10032243 3.08 Std 10032244 3.08 Posi 10032245 3.27 Std
10032246 3.27 Posi 10032248 3.45 Posi 10032250 3.70 Posi
10032268 3.08 Posi 10032270 3.27 Posi 10032272 3.45 Posi
10032274 3.70 Posi 14085324 3.42 Posi 14085325 3.42 Std
14085326 3.75 Std 14085327 3.73 Std
1986:
10032270 3.27 Posi 10032272 3.45 Posi 10032274 3.70 Posi
10040660 2.77 Posi
1987:
4ET 2.77 Posi 4EU 3.27 Posi 4EW 3.45 Posi
1988: 4ET 2.77 Posi 4EU 3.27 Posi 4EW 3.45 Posi 1989: 4ET 2.77 Posi 4EU 3.27 Posi 4EW 3.45 Posi

Blue 90 RS

Night rider - thanks for the info. That'll be most helpful!

big gear head

Night rider, his '90 should already have 28 spline axles.

RedLeader289

iTrader: (2)

I have a 3.27 9-bolt posi, with the 'bad' brakes. The calipers have been rebuilt, fresh rotors and pads, I have behind a built th350 and a hard shift kit and I couldn't ask for more. Got it for 75 bucks , it was sitting behind a gas station, outside (no idea how long). It's a pretty stout rear end. If you can get it for a good price.

*edit* Ran it for...6 years now, I think? something like that.

Night rider327

iTrader: (13)

BGH... I thought '90 was the 'change over' year where who knows what it has unless you take it apart.. I thought some 1990's got 26 and others got 28 spline and the full every third gen got 28 spline axles wasn't until 1991

Blue 90 RS

For the record: my car currently has a 3.23 rear from a 1989 TransAm. It was the optional ratio behind an automatic. I don't have the original.

big gear head

I think '89 was the year that some of the later cars got 28 spline axles, but I can't say for sure. As far as I know all of the '90s had 28 splines. It was also the year that the 8.5 got 30 spline axles.

That '89 TA rear end probably has 26 spline axles, but you can check to be sure.

Night rider327

iTrader: (13)

Oh cool, thanks BGH. I guess I was a year off on my thinking.

TTOP350

iTrader: (8)

Is it the 10 bolt or 9bolt? A 89 Trans Am with that gear should have the 3.27 9bolt.

Check and see for sure what you have now. (if you haven't)

Blue 90 RS

It is a 10-bolt.

Formula 305

I built a rear end this spring, my goals were pretty much identical to yours, 3.42s, posi, disc brakes. Here is the thread: https://www.thirdgen.org/forums/brak...rake-swap.html

It's been in the car since shortly after memorial day, so almost 5 months and I'm very happy with it.