From the outside without taking off the cover? I turned in the axle code but Chev dealer does not seem to know which it is.

 

if its stock in your truck you have the 10.5"

 

Nah, the one in my truck is the 9.5inch SF one. I bought one from a wrecked 2004 2500HD with only 5k miles on it. The axel is HUGE and full floating I tried the VIN number, but GM could only tell me it was 4.10 gears. I tried the code stamped on the axel, but that didnt get me anywhere.

 

ya, i thought you had a 2500HD for some reason, just now looked at sig

do you know what motor the wrecked 2500hd had

2500HD w/ 6.0 = 10.5"
2500HD w/ 8.1L OR DMAX = 11.5"

 

AAM 14 bolt 11.5

Corporate 14 bolt 10.5

 

yea, the 2500 had a 6.0L. from those pics looks like a 10.5".

 

How about a pic of that Blue Beast?

 

My friend...you'll just ahve to remove the cover...and break out the ol' Tape measure.