after searching on this topic i still have some questions. ok so i have a(1991 rs) 2.73 open drum rear that i want to swap out for an 88 gta 9 bolt posi disc rearend that is for sale locally. i believe i have read that you dont need a proportioning valve if your car is newer than 90 is this correct? what are the 9 bolt gear ratios? the guy says its a 3.30. anything else i should look for/need for this swap. thanks for your time, i appreciate it

 

Your current master cylinder is correct; IIRC, some members have run the disc/drum combo valve (but I'd swap it out myself for a disc/disc); the 9-bolt would be a 3.27, so, of course, you'll need to change the drive/driven gears to achieve a correct speedo reading.

You may find the following links helpful:

https://www.thirdgen.org/forums/faq-...now-about.html

http://www.transmissioncenter.net/sp...n_______va.htm

And if you should ever desire to swap in PBR's:

https://www.thirdgen.org/forums/faq-...iscs-89-a.html

JamesC

 

The swap from the 10-bolt to the 9-bolt you will need the proportioning valve and the parking brake cables. Been there and done it.

 

anyone know if autozone would carry the proportioning valve/ ebrake cables? is $200 a good deal for a 3.27 posi disc 9 bolt?

 

Proportioning valve, possible. Parking brake cables for a 9-bolt are next to impossible to find. That is why you need to get them off the donor car or you will be SOL. $200 is not bad but it will have the iron 10.5 and not the PBR 11.655 ones. 10-bolt cables will not work.

 

Two seconds quicker, DJP

For the combo valve, you might consider a boneyard or the classifieds here. GM should still have what you need, I'd guess. I doubt that AutoZone would carry the valve, but you should be able to order the cables--as a matter of fact, you might try Ed Miller for both as he carries quite a few parts. Perhaps DJP can jump in with more cable info, though I believe he's running PBR's, and whether the cables are the same or not, I'm unsure. I'd think $200 for the rear end would be in the ballpark.

JamesC

 

what are the 9 bolt rated at hp/tq wise? they are stronger than say a 3.23 posi disc 10 bolt? right

 

Some stronger, yes. The trade-off is that parts for the 9-bolt are, as DJP intimated, difficult to find.

JamesC

 

well i'm glad found his post. i'm also doing the swap but i have an 89 formula 350 rear end tag says its a 3.27. i pulled cables and all. but forot the valve. but my questions if you wish to answer.

1. I hear that the posi's are prone to wear out.
2. PART FINDINGS FOR THEM
3. Can i take Disc set up and swap to my 10 bolt

 

Forget the heresay about any weakness in the 9-bolt.
Also unless you are a harecore racer what are you going to break, normal wear items are available and the Limited Slip (not Posi) is not a worry as in a 10-bolt. With a 89 you have the best 9-bolt available with the 11.655 rotors and a 3:27 ratio. Just install it and the proportioning vavle is not a problem.

 

1. No experience (but wear is part and parcel of running a car).
2. Discussed above.
3. Yes, with the proper backing plate. Note the above link.

JamesC

 

no as stated in the title have an 2.73 open,drum 10 bolt. iideally m looking for a 3.23+ posi disc rearend from a third gen but i just happened to find a 9 bolt, thats y i was curous

 

Jump on it.

 

i offered him 175 because he is unsure of the mileage. im just waiting for him to reply. i also need to findout if he has the ebrake cables

 

question about speedo gears. i have 2.73 gears now and the 9bolt has 3.27 gears. i read the tech article but dont know what sets came stock and what i would need to swap to inorder to have a properly functioning speedo. help please!

 

Install kits are not a problem. There are several sites on the net that sell them. T/A performance manufactures a rear cover. Moser makes custom axles for them(I've got a pair in my garage waiting to go in). You can get a new carrier and posi cones from Australia. The shipping costs are higher than usual but the cost of the carrier itself is comparable to any 10 bolt carrier.

 

ended picking up the rear(3.27, posi, disc) also got the porportioning valve, larger front and rear sway bars and an extra torque arm for $190. didnt ebrake cable. where can i get this part? gm? websites? also have to get 45 tooth driven gear and driven gear housing.