How do you tell if a trans is LSD when it is out of the car or not? I've had an extra one sitting here and I'm not sure if it's LSD or not, and cannot remember how to tell. Is the casting number different or is there another way to tell? Thanks.

 

turn the hub. If both sides go the same direction then it is a lsd, if they spin opposite of each other it is a open diff.

 

Thanks, I knew it was something like that, but I couldnt remember.

 

So, what do you have?

 

Oh, I have a spare Open Diff trans.

 

Whats stamped on the tranny up on top, near the front? It will be the tranny code.

 

Actually kevin.. i don't think that works. When i had the tranny out of my car we did the same. They spinned the opposite direction. Then again, i could be wrong.. its been a while since i did the clutch job. However, I have the LSD option code on the sticker and have tested it to see if it was LSD. (umm auto-x.. dumping the clutch at 3k )

 

Limited slip will "slip" when you hold one hub and turn the other. It locks when going straight, and when turning it lets one side turn faster. Turning one hub and the other going same direction means a LSD, or Posi (I hope you don't have posi...haha).

Now if you had a LSD, you could do this. Turn the right hub, and hold the left one, but let is lip some, they should turn at different speeds. when traction is equal, they'll both spin at same time.

It's basically a Posi-traction (Locked) diff, with an open diff around turns and what not.

 

Thanks for the clarification BigNNasty. I know we had to turn both wheels at the same time to get the splines lined up. Maybe I was just thinking of the sliping action when turning just one.

 

You can tell what I'm talking about when you do a Brake Torque in a Open Diff car, and a LSD car.

Open Diff- 1 Mark
LSD- 2 Marks

 

OR you can find, read and research the tranny code number that is stamped ON the tranny.........then there will be no guessing,opinions, or whatever..........just check the number on it.

 

<<Turning one hub and the other going same direction means a LSD, or Posi >>

Posi (or positraction) is GM's name for LSD.

 

Thanks for all the info guys.

 

Posi trac is a locked diff, if I'm correct.

Well, I'm not 100% sure on it, but it is atleast a LSD like you said reactor.

All I know is my grandpas 427 67 Chevelle has one...mmm that thing could probably scoot!