I'm looking for a limited slip 3rd member for a 9" rearend. Can anyone tell me what vehicles came with this original equipment.

 

They would be worn out by now. Just try the normal ring and pinion vendors.

 

They were normally a special order item when purchased new, not specific to any certain vehicle. Fairly common in some of the old police cars, and I've found a few in some old Lincoln's and a few more in some of the muscle cars--Mustangs, Torinos, etc. There are a lot of vendor's selling new units in the $300 to $500 price range. A used one at a minimum would need rebuilding, probably new bearings and other parts. I've bought used ones anywhere from $50 to $250. Kind of depends on how much searching you want to do and how much time and money you want to spend rebuilding one......

 

Just a note on used one's - Lots of people think they have LS, but they do not. It is easy to spot the difference as the bolts that hold the ring gear are different sizes, and the pinion housing is cast different around those bolt holes.

I bought a limited slip on eBay, but received a standard open rear end. In the end eBay forced the seller to give my money back, but I had to eat the shipping both ways.

Later I bought a new, never used Detroit Locker for the rear end for $60, and spent another $50 in parts rebuilding my original rear. I like it better than a Limited Slip, and there are no clutches to wear out. I understand lockers can give you trouble steering on ice, but have never experanced that - I live in California.

I also understand Detroit has a new series of lockers that are better about that. I would consider a locker in place of LS, if I was you.

 

Most any 9" that has a letter in its' Identification code will be some form of traction control differential.

What you gotta watch is whether you have 28 or 31 spline axles in your rear & the donor rear has same number of splines as the rear you have. . . .

FBp

 

Is there a way to find out how many splines a rearend has without taking it apart? My truck drives great I would rather not take it apart without the new parts to put back in.

 

There is a 99% chance your rear is 28 spline, if it is original.
And no, the only way to confirm it is to remove an axle - but that isn't as hard as it sounds. You can have one in about 20 minutes; less is you have air tools.