vetklr, I have a Powertrax no-slip in my 8.8. When I installed it I couldn't get it to "test" on the jackstands. I really didn't think it was going to work.
The first time I drove it my suspicions were confirmed, it seemed to slip and jerk a lot. After some sharp left and right turns and a couple of backups it started working as advertised. Now it will "test" on jackstands and I love it.
I dunno, maybe the
oil has to work it's way inside or something.
I suggest you put some driving time on it before final judgement.
Ed