Howdy! A couple months back I had a Cusco 1.5-way LSD installed by Rallispec in the rear of my Legacy. I immediately noticed that it was wicked tight - lots of popping and clunking during slow speed maneuvers, to the point the car would actually surge (like I didn't know how to drive stick) as I pulled around a corner. Rallispec had I think used Motul fluid in it, and told me to give it a couple/few hundred miles to break it in. They also said to find an empty lot and do some tight figure-8 turns to help break it in. So, I did that, and even after 1000 miles the thing sounded/felt the same.

I drained the fluid, and replaced with Mobil1 + a tube of friction modifier for clutch type LSDs. Went and did the figure-8s again and voila! no more noise. Well, it wasn't completely gone, but it was probably 90% gone, and the car felt much better.

Everything was hunky dory for about 6 weeks or so, and then I did a track event at VIR. I'm not sure it's directly related to that, since the change didn't occur immediately, but about a week or so after the track event the diff started to really clunk and pop a lot again. I haven't drained the fluid yet, but my guess is that maybe I cooked it with the track sessions? I dunno.

So, I'm curious what fluid others are using with their Cusco LSDs. I'm hoping that there's an option out there, and not just "That's the way LSDs are, suck it up."

Thanks,
Pat Olsen
'97 Legacy 2.5GT sedan

This sounds similar to a binding center diff problem I had about a week ago. Only did this in turns.

My Cusco RS 1.5 way (for a Nissan 240SX) popped and clunked a decent amount on any synthetic. I switched to Valvoline 80w-140 semi-synthentic, and voila! All quiet again.

Well, I have all sorts of things in my garage, so I think I'm going to try some Redline Shockproof next. Their description makes it sound like it can help with stubborn LSDs, so we'll see...

Pat

Pat, let us know how the shockproof works out.
I use it all the time in my car.

Pat