Im asking this for a friend, he wants to put 4.10 gears and a mini spool in his 2001 5.3 swb gmc sierra 1500. Does he have an 8.5 10 bolt or an 8.6 because a friend of ours told him he has a 8.6. Also what do guys sugg. he buy, he knows he wants 4.10's and a posi, but does he really need a mini spool. He only uses it as a daily driver and maybe he might bring it to the track twice a year. Thanks in advance

 

Good lord, if this is his daily driver, don't put a spool in it! Get a posi like an eaton or auburn! 4.10's are great too imo, and yes he has the 8.6" rearend. It's very similar to the 8.5, with a few internal differences.

 

They dont make a mini spool for an 8.6. You can use the 8.5 unit, but it will fit loose and probably not last very long at all. Tel him to just do an eaton or detroit locker.

 

8.6 can use the same gasket as the 8.5, but different bearrings for the carrier

99+ is 8.6, 10 bolt, 30 spline

 

The internal parts for the carrier are also different, not just the bearing size on the carrier. That is why the mini spool wont fit properly. A full spool would fit because some of them use the larger bearing, but that would require a c-clip eliminator kit.