9 Bolt Rear

[Zero4488]

I have a 1986 Pontiac Trans Am with a 9 bolt rear and rear disc brakes....does anyone know what the stock ratios are in that 9 bolt....cause I wanna know the difference after I put the 3.73's in it....

[Tru2Chevy]

It would have 2.77s, 3.27s, or 3.45s from the factory....

- Justin

[rgaynor85]

wait do u mean 9" inch if so i dont think there is a "stock ratio" whatever u buy in there is what they come with. inless u mean stock 10bolt but i think u need to clarify, or did gm make a 9bolt and i didnt know it

[Zero4488]

No...I mean I nine bolt....from what I hear it's an Aunstralian rear....but thats their could be no fact to that...but it is a 9 bolt.....

[84HOtransam]

wait do u mean 9" inch if so i dont think there is a "stock ratio" whatever u buy in there is what they come with. inless u mean stock 10bolt but i think u need to clarify, or did gm make a 9bolt and i didnt know it

gm used a 9 bolt in some of the later third gens... and the ratios were as stated above..

from what i also know its tough and expensive to get gears and carriers for the nine bolt...but they are stronger than a 10 bolt..

[V]

i would safely assume you have 2.77 gears, since you have a 305tpi/auto trans.

and like 84HOtransam said, it is very hard to find aftermarket gears for the 9 bolt.
The 9 bolt is, i think, made by borg-warner and like justin said, only came with 2.77s 3.27s and 3.45s

I would recommend trying to find a set of oem 3.45 and install those if you want to keep your 9 bolt, and you would also need the carrier for the 3.45s since i dont think itll fit the one with 2.77s and tryign to find the proper ring gear spacer may be just as hard as finding aftermarket gears.

[Tru2Chevy]

You can find some aftermarket gears, but not many. 9bolt.com shut down now, not sure if ring-pinion.com carries 9-bolt stuff or not.

Best bet for gears is to either go junkyard hunting or search TGO.

- Justin

[V]

i checked on www.ring-pinion.com (http://www.ring-pinion.com) and the 9 bolt is also the 7.75 GM rear. this is what they have listed. the oem gears they have are the same as what we know came stock, but i didnt see any other options

GM 7.75-277 7.75" 2.77 R&P (OEM) General Motors 7.75 2.77
GM 7.75-327 7.75" GM 3.27 R&P (OEM) General Motors 7.75 3.27
GM 7.75-345 7.75" GM 3.45 R&P (OEM) General Motors 7.75 3.45

[Tru2Chevy]

Yea, I'm pretty sure that's the right ring size for the 9 bolt.

- Justin

[BonzoHansen]

i would safely assume you have 2.77 gears, since you have a 305tpi/auto trans.I got a 3.27 from an 85 TA 305TPI/AUTO car.

[V]

ok well then 2.77 or 3.27... perhaps the 350 cars got the 2.77 more often, cuz now that you mention it, my one 88 GTA had 3.27s as well

[BonzoHansen]

3.27s and 3.45s are both nice street gears, esp with these late model autos with steep 1st gears.

[johnjzjz]

AS A QUICK REFERENCE YOU CAN COUNT THE PINION TURNS TO DISC ROTOR TURNS AND GET CLOSE TO SEE WHAT YOU HAVE FOR EXAMPLE 3 TURNS OF PINION AND ALMOST ONE TURN OF THE BRAKE ROTOR KIND OF WILL GIVE YOU A 3"08 GEAR RATIO NOT PERFECT BUT CLOSE JZ

[V]

you can check you RPO codes(specific vehicle options)
The RPO code list will either be inside your center console or in the drivers side trunk storage compartment. You will have one of the following:

GH3 : AXLE REAR, 2.77 RATIO
GW6 : AXLE REAR, 3.27 RATIO
GM3 : AXLE REAR, 3.45 RATIO

[Ian]

My 87 GTA (L98/auto) had 3.27 gears. Like paul said, just check the RPO's to see what you have

[project89]

strange carries 3:70 gears for the 9 bolt as well,and i belive they also carry the bearings/seals as well,though im pretty sure u can still get those form a good parts house (i.e not pepboys or autozone)

[Zero4488]

Ok...well I found the gears for my 9-bolt....but now I am currently looking for a carrier....any ideas?

[project89]

do u need a carrier or do u just have a worn out posi unit,if urs is just worn out.i may be able to get u a clutch kit for the 9 bolt posi

[Zero4488]

I need a new carrier for 3.73 gears....I have carrier 1 for my 2.77, I need carrier 2 for 3.73's.....

[project89]

im at work now so ill make some calls to see if i can get a new 9 bolt carrier,or a used one.if i find any ill pm u the prices

[Zero4488]

Thanks alot man....

[alamantia]

Does anyone know for sure what internal parts are interchangeable between the 9 bolt and the 10 bolt?

In other words, if I had a broken 9 bolt in a 1988 camaro and an old 10 bolt out of a 1989 camaro laying around and didnt want to swap the entire rear axle, could I just replace the broken parts by swaping them if I had to?

Axles
Carrier
Ring & Pinion

Thanx

[V]

nothing is interchangeable internally...

[alamantia]

Not even axles?

[V]

nope

[alamantia]

Ok thanks.