anyone who has made this change... please elaborate... what kind you got? how much it cost? what kind of work involved? thx

 

Are you trying to convert your drum axle to disc, or simply swap in a disc axle?

 

whichever is better, easier, and cheaper... which one should i do?

 

Swap in a disc axle. Preferable one that's got the 89-92 single piston aluminum calipers on them.

That's pretty easy to do. All you'd have to change is the proportioning valve. It'd probably be cheaper too.

 

anyone know about how much that will cost?

 

It depends on the gears, axle splines (26/28), posi, 9-bolt or 10-bolt, etc etc...

What rear do you have in your car now? If you've got a 3.73 posi or something like that in good shape it might be worth your while to convert it to disc. The housing requires fabrication to mount the backing plates on.

Since yours is an 89GTA, I'm surprised it doesn't already have discs. Do you have a 9-bolt or a 10-bolt?

 

yeah... well... the gta is a 305 that has rear drums... quite dissapointing for me... but the price was right... right now it has a 9 bolt in it... and i haven't changed the gear... but im pretty sure it has a 2.73 gear...

 

It's a 2.77 9-bolt? Yuck. I can't think of anything worth saving from that rear, except maybe the rear cover and the axles.

Get a new rear. I sold a 10-bolt posi disc for $250 (it was a little cheap since I'd exploded the previous posi) with the old style discs. Paid $100 for the aluminum single pistons and rotors and ~$600 for a rebuilt 3.70 9-bolt.

That's probably about the range you're looking in. The newer disc brakes drive the value up, posi is more expensive, gears above 3.42/3.45 are more expensive, and 9-bolts are more expensive than 10-bolts.

 

i just bought a 91Z28's rear end with disc, posi, and 3.42's. when i put it in ill tell u how it went.

 

I should have a drum-todisc rear brake conversion kit available very soon. It really is sweet.

Thanx,ANDYZ28

 

Andy,

If you do have such a kit, that'd be a great thing to have. But I don't think it's too useful in this case for a couple reasons.

One, the whole rear really has nothing too useful about it. An open 2.77 drum 9-bolt is not a good rear period. You'd be money ahead to simply swap in a better rear with better gears.

Second, is your kit going to even work on a 9-bolt? Remember the non-c-clip design requires positive retention on the end of the axle tube.

If he had a 3.45 or 3.42 posi rear it might be worth converting the brakes, but...

 

I am going to do the 10 bolt conversion first. Then the 9 bolt conversion.

I will keep you posted.

Thanx,ANDYZ28

 

well guys... i think after doing some talking to some guys this weekend... i am just gonna go get a 4th gen rear with a 3.42 gear and do that... gets my gear out of the way... and my disc brakes... thx for the help

 

I was gonna do that also on my '86 IROCZ. But I would have to also use 4th gen wheels. I don't want to do that. I like my 3rdgen IROC wheels.

Thanx,ANDYZ28

 

Theres a tech article on swapping on LS1 Rear disk. Using www.car-part.com you can get MISC parts for core and probly put it on for about 2-250.... No serious mods to make fit either...

 

Do the LS1 disc brakes work on a 9-bolt? I think you'd have to do something about axle retention. I would have suggested looking into it anyway, except for the 2.77 gears.

 

the conversion say's for 10-12 bolt. but why it would not work on any GM rear axle???... axle retention stays the same. Your only removing the backing plate and replacing it with a LS1 type, and drilling new mounting holes in the axle flange. Everything else is the same.

So thinking like that as long as the flange was large enough on the 9 bolt it should still work fine... It does fit stock 15" rims...

 

No, it's not.

10 and 12 bolts use a c-clip retention mechanism in the diff carrier. 9-bolts have no clips and are hammered in and held in with backing plate, which IIRC, has an axle seal built into it (very similar to a 9" F*rd).