LSD acting like welded diff

[Ptrain]

I bought a used cusco LSD off here and had a shop near me install it. Now after installation it's acting like a welded diff. As I go around corners the wheels hop like crazy. I tried driving in figure 8s in a parking lot for 20min to see if I can get it loosened up a bit but there wasn't any change. I have driven the car around a bit and it runs fine otherwise but when I go around a tight corner I can feel that the diff is fully locked.

Today I removed the pumpkin and poped it open to take a look at the diff myself and the diff is really wedged in there. I tried for a while to get it out but couldn't get it to budge. The diff won't spin either.

Do you guys think my problems come from an improper installation or the diff itself?

[jr_ss]

Sounds like they didn't shim it correctly. With the case open, you should be able to spin the diff by the input shaft/pinion flange or either of the of the output flanges.

[Rich260z]

Improper shimming, it's too tight.

[Ptrain]

Just an update. I gave the diff to a cusco dealer near me and they reported back today that the diff internals were assembled incorrectly. They believed that was what caused the diff to act like it was locked.

They are currently rebuilding the diff for me so once I get it back in the car I'll let you guys know if it works.

[aga]

somebody should ask his money back...

[Ptrain]

And I just wanted to update again as info for people who might run into the same problems.

The diff is back in the car and I've been driving it around some. I can definitely feel a difference after I got it back from the shop but I'm still getting a ton of chattering in turns. The shop that adjusted the diff even said that it's currently in 1.5way mode and at it's least aggressive setting. Do all aftermarket LSDs do this? I've never put an aftermarket lsd in any of my cars so this just might come with the territory.

I found a thread on the miata forums and a guy there said that after contacting cusco about a similar problem cusco recommended that he switch to their diff oil. So I'll give that a try to see if I can pull into a parking spot without it sounding like I'm drifting.

Another idea, while unlikely, as to why I'm getting so much chatter is my tires suck. Maybe if I switched from my crappy 195 all seasons to a nice 215 summer the increased grip from the tires would force the diff to slip while under low load.