here's the add:

1996 firebird trans am limited slip rear differential with disc brakes, nice rotors $150

here's an e-mail i shot to the guy:

Hi, I was wondering what gear ratio it the diff has and if you have all of
the brake lines (including e-brake)

here's his response:

Hi,
No idea on the gearing, however it is a stock rear end out of a lt1 automatic 4 speed. Prob 3.83?
All lines are connected.

i have a stock 84z with drum brakes and i think years ago i jacked it up to confirm it was a peg leg. any thoughts on this? good deal? what should i look for if i decide to go and buy it?

 

You or he could check the ratio by dropping the cover. Check the following FAQ for more info about that. Also consider the combination valve, especially if your 84 has the old cast iron type which has SAE threads (the new alum version will have metric), speedo gears and parking brake cables.

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

You'll need a new combo valve as JamesC mentioned, but you won't be able to use the one from the 96 as its part of the ABS system and not interchangeable with a thirdgen. The gear ratio is definitely not a 3.83 as that is not a ratio that was used in a 10-bolt rear. Most likely its a 3.42 or 3.23. I recently picked up a complete rear from a 93 Trans Am(LT1/Auto Trans also) at the U-Pull closest to me and it had a 3.23 in it. I paid about the same for it so the price is definitely worth it if the LSD works.

If you've got the SAE brake lines you will need to change some things to get the rear to work due to needing a new combo valve. Unless you can find one from a disc brake car with SAE fittings. Otherwise, the easiest thing to do would be to cut off the ends of your current lines and re-flare them to fit the metric combo valve. The lines are the same size, just the fittings are different threads.

 

If it's from an automatic car, chances are it's a 2.73 gear - my 1997 Z28 is a 2.73 gear and it's an auto LT1 car just like that 1996. But the only way to know for sure is to remove the cover - gearing will be stamped in there - divide one number into the other and you'll have the ratio

 

You don't even have to do that, as the FAQ provides the info.

JamesC

 

would the easiest thing to do be to go to an auto yard and take the combo valve/all brake lines from a disc/disc 3rd gen and use that with the 4th gen rear?

or if i find an early year 3rd gen with disc/disc how can i tell if the combo valve has SAE fittings? then all i need is the combo valve and lines to the rear right?

and how do i tell if the posi is good? do i just spin one wheel and if they both spin is it good?

 

The link I post above is your best friend. Good luck.

JamesC