I have 57,000 milles on my '99 and it appears that I will be needing to replace the clutch pack on my differential. I did my aprx 15,000 mile gear lube change and it was black, ton's of goop on dipstick & drain plug (mag hytec). It had been shuddering on slow corners when pulling, now it does it under all loads(added over 12 oz of modifier). I need to know where to purchase the clutch packs, did a search and couldn't find much on the 'net'. Also, if there are any ideas out there as to failure causes or preventitive items that would preclude another early failure, I'm open to suggestions. Finally, some specs ... . auto trans, 3. 54 gears, 275 injectors, EZ Edge on 3, Highway towing 8000 lbs 75% of time,baby it the rest. Thanx!! Brett