Groan in the rear end of AWD Venture

[klemmy]

We just bought an 02 Venture with awd. On the way home from the used car dealer, it got a groan or rub noise in the back when taking sharp turns. After searching many threads here it appears a rear fluid change is in order. The versatrak fluid is very expensive. Does anyone know if you can successfully use amsoil or royal purple instead of the versatrak fluid?