do you have the right oil in there. If you do not have a specific limited slip oil in there the limited part is not effective.
I use mobil1 with a BG additive for limited slip diffs.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)