my 02 2500 hd takes syn 75-90 in the rear diff, for the front it takes 80-90 non synthetic, can i or has anyone pt synthetic in the front diff, also do i need any additive for the limited slip.

 

You should check with Royal Purple. They are really good about answering questions like that via email.

 

thank you ill give them a hollar

 

I just put in Royal Purple this weekend in the Rear Diff. I've been hearing a lot of good things about them and decided to pick up some. The nice thing about it is that it doesn't smell like the other stuff. Most of the other stuff stinks after a while.

 

Yup Im running out my stock of Penzoil then Im going to RP on all my fluids. If you go to this link and enter the word closeout on the coupon you can get a sweet deal.
http://www.partsamerica.com/default.aspx

 

You can use synthetic gear lube in the front diff just make sure to use the correct weight.
No need for any additive since the GM rear-ends are not limited-slip, if you have the G80 options it is an Eaton auto-locker and it requires no additive since there are no clutch packs.