Working on my car this past weekend, I noticed that I have a nine bolt rear. I thought I heard that this would indicate that I have the borg warner rear that went out on some thirdgens. Is this true? My car is an 87 iroc, 5.0 TPI 5sp with the G92 package. Thanks.

 

Yep, borg warner. Being that you have a 5-spd, you might even have 3.45's....

 

More than likely your car will have two tags attached by the cover bolts. One will tell you if its a posi the other will tell you what gear you have.

 

You DO have 3.45's. The 9-bolt Borg Warner was introduced* in 1987 on Camaros on:

1) G92 (3.45) equipped IROC-Z's and
2) L98 IROC-Z's (3.27)

*The 50 prototype 1986 350 IROC-Z's all came with the 9-bolt but cannot be considered the "first" as it was not a regular production vehicle.



------------------
Willie

Supercharged 1987 305 IROC-Z, Daily-Driver, Emissions-Legal.
Former Paxton (6-psig): 12.57 @ 111 mph.
Former Paxton (6-psig) & former 50-hp nitrous: 12.04 @ 114 mph.
Current ATI D1SC (Initially 10-psig): Projecting high 11's.
Future ATI D1SC (15-psig): Gotta catch them pesky 26-psig boosted TTA's!!

http://willie.camaro-firebird.org/

1987 "20th Anniversary Commemorative Edition" Z28 Convertible -- Super Chevy Show Class Winner, 1998.

 

I have an 85 trans am with 9bolt,was it offered in that year and would also be 3.45

 

My previous statement refers to Camaros only.

As for Firebirds, I believe (not confirmed) that the first Firebirds with the 9-bolt rear was 1986. Because the rear gear ratios are slightly different on the 9-bolt as opposed to the 10-bolt, you can easily check the RPO codes to determine which gear ratio originally came on the car. With that info, you can deduce whether it was a 9 or 10-bolt.

9-BOLT
2.77 ?
3.27 GW6
3.45 GM3

10-BOLT
GU2 2.73
GU4 3.08
GU5 3.23
GU6 3.42

Willie

 

1985 was the first year for 9-bolts in Trans Ams.

 

In order for me to add this information to my database, I need a some sort of proof. Citing a reference is always good. Even better is someone who shows one of the 9-bolt rear axle ratio code on their 1985 RPO sticker. Anyone?

Willie

 

It was 85 for the Firebirds Willie, but I cant document it because the documents went with the car when I sold the POS. Mine had the 2.77. I know it was original, I had all the documentation on the car including the window sticker, and stuff from PHS.

 

I have documentation showing '85 was the first year. I have owned three '85 Trans Ams with 9-bolt rearends. The '85 GM service manual has the 9-bolt listed with part numbers for each gear.

 

My 86 T/A(tpi) has a 9 bolt in it. Has the rear disc setup-also has the 3.27's.
My 89 had the same exact setup--disc etc.

 

Just came across this post. Did you get your proof? Otherwise, I'll be glad to oblige. I have all the original documents that came with my '85 T/A. They clearly show that it has the Borg-Warner diff. I can fax them to you.


------------------
-Greg

'85 Trans Am - WS6,TPI:
Original owner, original paint/engine/interior, plus the usual bolt-ons

 

just as a matter of interest where the 9 bolts where made (borg warner ) they where not even aware that they went into camaro,s at all ..learnt that last year when i organised buying the nos rears that they had left ..had to convince them they where for chevs as well !

 

hey i just found out that i had a nine bolt all along, i always thought i had a 10 bolt since the service manual said that the 9 bolts stopped in 1989 but i came to the conclusion. there were no 1990s made in 1990 so i guess it was made in 1989 when the 9bolts were in production still!
good deal i guess, now i want to find some 3.70 gears and have them installed!
but i think i will wait on the rearend since i plan on a moser 12bolt when i get back from the military! oh well it will all work out!!

------------------
Jarrad
1990 IROC-Z L98 350 TPI
TH-700R4
G92- 9 Bolt Borg-Warner 3.27gears
Bright Red Hardtop/ Grey Custom Interior

mods: AFPR, B&M megashifter-HD4ft cable, Underdrive Pulleys, Ported plenum, K&N's, Magnaflow muffler, Aluminum Driveshaft, Gutted Air Boxes w/ Ram Air, and more!!
soon to have new PAINT, and suspension work

DAILY DRIVER: 1991 S10 2.5L/5SPD -

 

my 85 trans am has the 9 bolt posi/disk rear. if u havent found proof ill scan my RPO sticker for you, let me know.....

------------------
1989 pontiac firebird
bright red exterior(just repainted)
grey interior
5 spd
305 TBI (stock)
WS.6 formula wheels
3.73 posi rear end
http://members.aol.com/j007golden/Mikey89.html
http://www.geocities.com/firebird/myfirebird.html
-------------------------
1985 trans am
factory bright yellow
4 wheel disks
16 inch wheels
305 TPI
power antenna and mirrors
t tops

 

Now that is interesting, because all the other 1990 cars I know of have 10-bolts!

 

i know kevin i thought the same thing. and when i first got the car i looked to see and i thought i counted 10 bolts, but i must be retarded because i have the plastic fill cap on the back and the two tags. i am for sure my car is a 1990 but it was made in AUGUST OF 1989 so i dont know what is up.
i was just about to order a 10 bolt aluminum cover, glad i didnt, but i would have used it on my S10, haha. but now i am just gonna wait and by that MOSER 12 BOLT. i cant wait. its 2300.00 but the govt will pay that! ARMY!!
and what can i do to strengthen that 9bolt? anything. and what gears are offered. i know a bunch about 10 bolts but i always skipped the 9 bolt guru. so i am lost now! any help? thanks!
and hey i know TRAXION has a 10 bolt, and his car looks the same as mine. i was wondering if my rear was changed but the original shocks and stuff are still there. and all the stuff looks stock, and susposedly the car was stock when i bought it. oh well its still kinda fast.
and i heard the 9bolts were stronger than the 10 bolts!

------------------
Jarrad
1990 IROC-Z L98 350 TPI
TH-700R4
G92- 9 Bolt Borg-Warner 3.27gears
Bright Red Hardtop/ Grey Custom Interior

mods: AFPR, B&M megashifter-HD4ft cable, Underdrive Pulleys, Ported plenum, K&N's, Magnaflow muffler, Aluminum Driveshaft, Gutted Air Boxes w/ Ram Air, and more!!
soon to have new PAINT, and suspension work

DAILY DRIVER: 1991 S10 2.5L/5SPD -

 

The 9-bolt is quite a bit stronger than the 10-bolt. I've heard of people running in the nines with them with no problems at all. I'm pushing 500+ horses through one of mine.