i have a 98 z71 with the 10 blot rear. the code is GT4 is that 3.73's? and is that lsd or open. in the dirt it will spin both. and if i power brake it they spin but leave no marks so i cant tell. ok thanks

 

if you have a G80 code in your glovebox then you have lsd. Not sure about the gear code though.

 

In Greggo's signature, there is a link to the RPO codes. You can find these codes and match them up to the ones on the list. That will tell you what gears you have as well as a lot more about the truck.

G80 is the factory 'locker' that only locks under 20mph if there is enough traction for it to grab something.

 

ok i the codes GT4 and G80 so i have 3.73's and the stock locker. and y does it only lock up under 20 mph?

 

It's a 'safety feature' to help keep you from loosing control around turns or something.