i would bet the seals need replacement. my 2001 450 had the same symptoms as yours and the seals fixxed the problem
also i noticed when the rear seal(drive shaft) was removed it looked new and intact while the the two side seals were worn,i only say this because the rear seal may not need replacing. noting the sive of tire and lift kit would only increase the chance of seal/bearing failure. one more thought you said you have play that should not be, if you pull the axels out put new clips in there.