Ok... here's the deal... my dad used to have a 91 Forumla Firebird, he loved that car. But while he was crossing a road in town this woman cut across 3 lanes of traffic doing about 70 (in a 45) and T-boned him. It picked the back end up and swung the car around and he hit another car. The wreck snapped the axel and caused body damage. The ins totaled out the car. He bought it and wanted to fix the car, but since has changed his mind and gotten a truck The truck had a 305 in it and we are planning on pulling the 350 out of the Firebird, rebuilding it and placing it in the truck . Dad would also like to try to take the rear end out of the Firebird and put it on the truck . However, my thoughts are instead of pulling the ENTIRE rear end out and having to worry about axel lengths etc, can you just take the differental and swap them? That would take the gearing and the posi-trac right? The truck is an 85 GMC Jimmy. One of my friends suggested putting something like 4.10 gears in but the problem with that is that it involves EXTRA money where as right now we have the gears, the only loss would be of time. I guess my question would be will this work? Can I take the differental out and <hopefully> have it hook up just fine. I mean both parts are made by GM, ya know?

 

If the truck is an S truck, then the differential (carrier) will go in it. If the truck is a full-size, then it will not.

You still need to know whether the carrier in the Firebird is a 2-series or a 3-series. Most of those would have come with a 2-series carrier, since they had 2.73 gears; in that case, it wouldn't be worth much to anybody.

 

S Truck? Sorry i only know basics of mechanics... What's an S Truck?

If you are saying that the Firebird 2 Series has 2.73 gears then i would have to say the Firebird has a 3 Series b/c the gearing is 3.27

 

Sorry... computer messed up and double posted...

 

S-10 or S-15

If the Firebird is really 3.27, then it's a 9-bolt, and nothing about it will fit any truck at all. AFAIK there's no 91 cars with 9-bolts, 89 was the last year. It might be a 3.23 10-bolt, in which case it is 3-series, and will probably be useful.

But I forgot one thing... even if it's a 10-bolt, the 91 carrier will have 28-spline side gears, and the 85 model if it's a S-15 Jimmy, will have 26-spline axles; so you'd need to get some 28-spline axles from a 90-up S truck to use the 91 carrier.

 

talked to dad he says its a Full Size 4WD Jimmy... and you were sayin that it wouldn't work.... anything ideas? and yea its a 3.23 10 bolt rear...