I am in the process of getting a rear disc brake, posi rear end for my car (Tomorrow) Is there a sticky, or a website that give details on changing the rear end (order of R and R) Or could onr of you guys that have done this give me some pointers??? I have never done this on a thirdgen before, and want to do this as easy as possible....Thanks for any help....Tom

 

Are you changing the gears as well or just adding a posi setup?

 

Im changing the whole thing...My car had 2.73 open rear end with drum brakes...This other rear came out of a 86, or 87 IROC Z-28. With TPI, and Automatic..So I figure it will have 3.23's, or 3.42's...I do not know which it has..(It was too muddy to get under and check it) I paid 300 dollars for it...With the sway bay (Which is bigger than what I have now) I hope it does not have 2.73's, but I cant imagine it would..It is complete Calipers, and all.Thanks for any replys, Tom

 

2.77 posi/disc rears were pretty common on automatic cars so check the ratio before you go to the trouble of swapping over. The swap itself is pretty simple. Put the car on jackstands and disconnect the rubber brake hose from the body side and leave it on the rear, and plug the line unless you want it dripping on you. Next pull the wheels and driveshaft, unhook the front of the torque arm from the mount on the trans, then disconnect LCA's and PHR from the rear. Watch out with the torque arm, it'll pinch your hand against the tranny tunnel if you give it a chance. Save the shocks for last as they support the weight of the rear when the subframe is on stands. Put a pair of stands under the axle tubes, or a floor jack under the chunk if someone else is there to help balance it. Disconnect the shocks, and pull the springs off their perches as you ease the rear end down. Pull the rear out from under the car, swap the torque arm over to the other rear, and put it all back together in reverse order.

 

Jaxom.... Man , I never even thought about it having the same gear as I have now...I hope is does not, because I have already paid for it...At the worst I will have disc brakes, and a posi..At the best I will have a better gear ratio also...On these cases you cant put a 3 something gear in a 2 something case can you????? I was not able to check it at the junk yard because it was raining cats, and dogs, muddy as hell....I've looked all around the Houston area for one of these, but didnt have much luck, or the people wanted more than 300 dollars (Which was my limit) Surly they would put a 2.73 in a IROC Z, would they??????? Please say no........Thanks for the info on doing the rear end..Tom

 

I have the factory rear out of my IROC sitting outside the back door to my shop, and it's a 2.77 posi/disc. The 9-bolt rears with good ratios are getting harder to find...3.45's are majorly rare now and 3.27 rears are tough to come by. I wish you the best of luck with it being a decent gearing, but odds say it's a 2.77 axle. Sorry man.

Oh and I believe you have to change carriers to go to a 3.27 or deeper gearing. Not 100% sure though....

 

Oh man that is gonna suck big time....Thanks...

 

richmond makes a thick gear 3.73 for a 2. series carrier, i have one in my 91 TA vert, i also have one in the closet,never used with precission install kit.
was going to put it in 87GTA, but swiched to a 97disc brake rear end to get the 4th gen ws6 wheels to fit.
i still have the recipt if any one wants to buy them e-mail me.

 

Here's how to determinne what ratio the rear is for a 10-bolt (jerk the diff cover and look): numbers are stamped on the ring and pinion:

41 : 15 = 2.73
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC

 

Hey TAtom, I might want that if mine has the 2.73 gear...Thanks, Tom,......

 

If it's a 9 bolt, it'll have a tag showing the ratio bolted to diff cover. ...but yeah, more than likely, it's a 2.77.

 

I have a 86 z28 when I got the camaro it has a 350 and a 700r4 trans my question is the camaro was a 5speed and now has the 700r4 I want to go back to a 5speed will the T5 bolt right up the 350 and the same drive shaft or will I have to change the drive shaft and did the 5speed camaros come with the T5


Thanks for any info

 

they make a WORLD of differance.btw my old rear end does not have a plate on diff cover stating gear ratio, hope this helps.
and i need a pic of how the power steering pump and brackets mount on a v belt car, if anyone can help i would apriciate it!!

 

The bellhousing and T-5 five speed transmission will bolt to the 350. The manual/auto driveshaft is the same.

JamesC

 

Yes they do, but that's for a 10-bolt rear end. If this axle came from an '86 or '87 IROC it's a 9-bolt. They're not compatible.

Good information, but again that's for a 10-bolt only.

 

Not entirely true. Check the tech data page on this site for 86 and 87, and you'll see that the majority of rears for those years have 10-bolt gearing. The rear end in my 85, for example, is from an 86. It's a 3.23 ten-bolt.

And, of course, the gear ratios above are for a 10-bolt. I've edited above to that effect.

JamesC

 

IIRC all L98 cars up to '89 should have been 9-bolt equipped, as well as LB9/T5 cars with the G92 option. GM didn't think the 10-bolt could handle the torque. Then in '90 they decided warranty replacement of the occasional 10-bolt was cheaper than importing the 9-bolt from Australia...that's my theory for why the 9-bolt got scragged.

You're right though....if it was an automatic 305 car it should be a 10-bolt.

 

the aussie rear ends usally had disc brakes, and i hear they were junk although i never had any problrm with the one on my old 86 T/A... RIP.

 

The major drawbacks to the 9 bolt rearend are that the posi units in them almost always go bad, and new replacement carriers are non-existent. There's also no choice of ratios when buying new gears for them. The only ratio available new is 3.70. 10 bolts are slightly weaker than the 9 bolts, but the vast availability of new parts you can get for them makes up the difference if you ask me.