Since I hosed the stock 10 bolt in my '86 Bird I'm looking to go down to the junkyard and swap something decent in there. Been getting conflicting information on rearends.

The one junkyard just has a pile of rearends laying in the corner. Will there be any markings on them to denote gear ratio and posi trac? It'd be a pretty big waste of time to just swap another 2.73 open diff rear into my car... Was looking at doing a 9 bolt swap. The disc brake conversion kind of scares me though. i'd almost rather leave the drums and just swap a decently low-geared posi-trac rearend into it.

Any information would be swell.

 

Posi and drums is a tough combo to find. The disc conversion isn't difficult anyway, so I'd go that route if you can. All you really need to do is swap the rear out, change the E-brake cables to the disc style, and possibly change the prop valve to a 4-wheel disc unit. The 9-bolt is a tough rearend, but hard to find parts for. Keep that in mind if the car is a daily driver.

The best way to find the ratio of a rear is to pull the cover, count the teeth, and divide the number of ring teeth by the number of pinion teeth. You can tell whether it's posi by looking at the diff...if you see springs, it's posi. If you just see 4 gears and a big pin through the middle, it's peg-leg.

 

There's a lot of goddamn teeth though... :P Thanks for the help.

Will I know a 9 bolt versus 10 bolt by looking at it? Anything major visually? (If someone says "It only has 9 bolts" I will personally find them and do...terrible terrible things )

 

it only has 9 bolts.....

lol

 

I've missed you cz28 guys. :P

 

You don't have to count all the teeth when you pull the cover. GM gears have the tooth count for the pinion and ring gear stamped into the outer edge of the ring gear. Just rotate it until you see this, then divide.

11/41 = 3.73 gears

The cover on a 9 bolt has 9 bolts, cover on a 10 bolt has 10 bolts. If you are lucky, the rear may still have the GM Posi tag on one of the cover bolts (about the size of a dogtag). I would still pop off the cover and check before you purchase.

- Justin

 

Get a 4th gen rear end.. and call it a day

 

10 bolt has a smooth cover. 9 bolt has a rubber plug in the cover. Dana 44 (good luck finding one for a third gen in the junkyard) has a metal plug in the rear cover.

 

Ok...so I have my '97 Trans Am locker 3.42 rearend sitting here. Its longer then the old one, yes? So my old rims/tires will stick out farther? Do I need adapters or something goofy to make my old rims work with the new rearend? How does that **** work.

Any thoughts on how to beef up this rearend without pulling it apart? Can I weld the axle tubes to the differential without pulling out the gears, etc.? I already have a TA stud cover and a half-dozen quarts of redlien fluid.

 

Your stock rims will stick out about 2" on both sides, mine were flush with the outer lip on the fender flare. If you switch to 4th gen rims, you will not need spacers and they'll tuck under your flares like the stock 3rd gens rims did, but you'll need 2" spacers in the front. Everything will bolt up fine though, except brake lines going from drum to disc. You can bend/buy new lines for a thirdgen with disc and strech them a little on each side to make them fit ok. I dont know what to do with LT1 style ebrakes, but stock thirdgen disc cables may work, dont quote me on it as I have an LS1 10-bolt rear end.

http://www.ws6transam.org/10bolt.html
Daniel Burk has a pretty good writeup on 10-bolt build ups.

 

Ok, I'm apparently having a really slow day. This whole rim offset/tires/axles thing is blowing my mind. People are telling me that in order to run wide tires (like 17x9 TTII's) I'd have to get spacers all the way around on my stock axles anyways, so the LT1 rearend being wider doesn't really matter. If this is true, fine. I plan to get a moser 12, end result...this new rearend is to just hold me over. Would I get a fourth gen moser then? I'm just trying to put some decent sized rims and tires on there, with disc brakes, posi and a decent rearend ratio until I can afford the damn $2000 moser. If any of you guys can message me on AIM, that'd be cool---Don't want to waste any more thread on me just failing to grasp this ****!