Okay, I am going to be looking at a 1995 Formula rear... Car had a 6 speed.

The 6 speed would make the rear gears 3.42 correct? And the Auto's got 3.23?

What type of Posi is it? Auburn? Eaton? And how long do they usually last?

Also, what is the brake size? 11.65? While the Ls1 rear got 12" brakes?

I found one for $130... Should I wait and pick up an Ls1 rear with bigger brakes for about $250?

And what is the best way of testing them? Can they be rebuilt?

 

yes, 6 speeds are 3.42's and i do believe lt1 rear brakes are 11"-11.5"

 

The only way to know for sure what the rear gears are is to take the cover off and check - there's mo short cut for this - a 1996 rear is 14 years old - anyone could have changed gears in 14 years.

 

The LT1 rear is the same brakes as a 89-92, only on a wider axle. Not even real sure the diff is different. If so? Just swap the parts & your done, without the wider axle. Depends on what wheels you are running.

Get a LS1 rear & you'll get bigger/better brakes & a better diff. No sense in putting in a LT1 rear, when the brakes are no better than what the 89-92 3rd gens came with.

 

I currently have 88 brakes, so anything is better for now... I plan on buying a totalled low mileage 4th gen in the future for an Ls1 swap, so when I do that i'll snag that rear... I just need something for a year or two.

 

Get the later model torsen diff 99-02 because they dont wear out. The 93-98 auburn is a clutch type that does wear out and maybe done for already. and make sure it doesnt have traction control because then you will have to swap the hard lines.

 

Yeah, that is what I have decided to do. I decided to work on my interior, and just buy a Totalled 4th gen for my Ls1 swap, and just take the whole drivetrain.

 

the $.02 i can put in is - i just looked at a ls1 rear end and it was not posi although it was a LSD rear, and yeah 3.42 gears for the 6spd so make sure you know what your buying before you get it

 

If the rear is out of a Camaro or Trans Am yes it's 3.42. Some Firebird Formula 6 speed cars came with 3.23's in them.

 

How do you know it wasnt posi? You have to pull the diff cover to be sure, doing the old spin one tire and see if the other spins the same way doesn't work with these differentials. when i got mine i spun one side and the other did nothing and i freaked and made a post and someone pointed me to wikipedia and i learned alot

 

Yeah the torsen diffs in the later year LS1 rears are nice diffs and they dont work like a normal posi like above mentioned. If it came froma V8 car its more than likely a posi

 

LSD = Limited Slip Differential = Posi

Posi-Traction is a trademarked name for a limited slip differential. LSD IS Posi!