fst2qtrmile

ok local shop guy here is helping me with my rear end. NOBODY HERE KNOWS HOW TO REBUILD A 9 BOLT or even wants to try to. My buddy says that he would try but why waste the money when its gunna break again. 9 BOLT OUT OF THE PICTURE!!! not an option. so here are the choices.... He told me he rebuilt a 8 1/2" that was in his 88 IROC and he is sure it was a 8 1/2". never to my knowledge did they come with that. He said thats what it came with in the car but possibly someone swapped it out. He wasnt sure, all he knew is that it was a 8 1/2" when he took it apart and rebuilt it. I know the grand nationals came with a 8 1/2". Next is a ford 9" rear end. pretty basic rear end but what year make model do i look for and take rear end??? what specs etc.??? Next is to rebuild a 10 bolt 7.5, put a strong posi carrier in it and hope it last, but what carrier would actually hold up to my set up???

So the question is, what rear end??? 8 1/2" , ford 9" or 7.5" I am on a budget here. whatever is the cheapest but also keep in mind what would last longer. I drive it hard. I do launch alot.

Also some feedback on how he had a 8 1/2" rear end in his 88 iroc... u think sumone swapped it??? please help as my 3 rd rear end is going to shhitt

fst2qtrmile

also if anyone knows of another rear end then let me know. an LS1 rear end maybe??? i did my homework on that 8.5" seems like it was in the 2nd gen. I dunno if they will fit my third gen. Also the G-body rear ends... hard to convert. ALL FEEDBACK WELCOME. Please talk from expierence

AlkyIROC

The only 8.5" that came in a third gen was the rare Dana44 but don't expect to find one under any cars in the junk yards. The only factory diff that will bolt into a third gen is from another third gen or from a fourth gen. That leaves you with the 7-1/2 or 7-5/8 GM 10 bolt or another 9 bolt.

A bolt in 9" or 12 bolt is available from Moser and Currie but a complete diff will cost you between $2000 and $2500.

Finding a junkyard 9" diff that will fit isn't hard however trying to adapt the third gen torque arm system isn't something for the average backyard mechanic. By the time you're done adapting and modifying to make a junkyard 9" work, you could buy a good, complete aftermarket diff for about the same price.

My 9" housing is out of a 1970 F100 just because it was close enough to a third gen diff width. Strange axles. A standard factory center section with strange spool and some 4.56 gears. Brakes are large ford drum brakes. I don't have a park brake system and my rims are dual bolt pattern to fit GM or Ford wheel studs. The diff is installed with some ladder bars so I didn't have to worry about finding a way to install a torque arm.

Redliner

It's been a while since I have even thought about cars since I sold my Camaro.....sniff. I have no idea how much power you are putting down, but I see no reason why not to just get a 4th gen rear and put it down there. Okay there are some drawbacks; Zexel torsen Posi, disc brakes, any gearing you choose, and 2inches wider, it bolts into a 3rd gen. Well okay those are advantages. The gearing can be chosen by what came from the factory, If you come across an SS the Zexel unit has been upgraded. Should be able to find one on 4th gen pages for round about 200.

fst2qtrmile

i made up my mind. im using the 4th gen rear end. what do i need to complete it?? shocks, springs, driveshaft, etc???

DuronClocker

iTrader: (1)

Keep in mind a 4th gen (or even "LS1 rear end") rear end is no better than the 10-bolts that most of our cars came with. This would be the cheapest option, but not very wise if you keep breaking rear ends.

The strongest option would be a 12-bolt or a 9", but as I said these are expensive. Worth it? Definitely, if you're putting down the power.

If you want something cheap that will last, rebuild your 9-bolt. Rebuilding a 9-bolt isn't "cheap" per se but when you start talking about $2000-2500 for a 9" or a 12-bolt, then it sounds pretty cheap. They are MUCH stronger than a 10-bolt if built properly. Supposed to be able to handle some 450-500HP (of course this is just a number, depends how you treat it).

fst2qtrmile

nobody here can rebuild a ( bolt. im sure if i get the LS1 rear end that if i break it, it would be easier to find another. The only reason why im breaking rear ends is because brake cones are bad in all 9 bolts unless u replace them and nobody wants to here within 50 miles. So im sure a 4th gen rear end would hold up nice being newer than the 9 bolts and less miles. maybe when i start puting down serious HP, then i would consider a stronger rear end. Maybe just for now, 4th gen rear end with a a quick overhaul done to it. But first, i need to know something. Do i use the 4th gen driveshaft or mine already in here??? shocks the same, springs the same??? help me out here guys...thanks

Redliner

As far as I know everything is the same. All of the connections are the same. Keep in mind that chasis remained pretty much unchanged 82-02. The driveshaft should be the same, but lets see what others have to say from experience. Worst case senario: a drive shaft repair shop could cut off the old universal joint and weld on another that matches the length or cups.

DuronClocker

iTrader: (1)

Drive shaft is identical. Everything will bolt right in, but if you are using your stock rims, they will stick out 1 5/8" further on each side than they do right now. With stock rear 16x8 rims and 245/50R16s, the tire edges will probably be perfectly lined up with the fender lip. I have a rear out of a '98 TA in my car.

If you've broken 3 rear ends already, you're either abusing the hell out of them or putting out too much power. Either way, that 10-bolt will be toast shortly too I'm sure. A 9-bolt is MUCH stronger than a 10-bolt whether its a 3rd gen rear or 4th gen rear (they didn't change at all except the axles got 1 5/8" longer on each side)!.

fst2qtrmile

yeah but suspect that a newer 10 bolt will hold up longer, and the way i go through these 9 bolts it rediculous. Its because all 9 bolts i come across have bad brake cones. I will see how a 4th gen works for me. I only can try, hopefully i get lucky and it lasts till winter. So everythin bolts right up huh???? nice...Seen as how u did the swap, i have no choice but to take your word for it