What kind of mileage are you guys seeing with the 8.1's? I'm looking at a 4x4 2500 Burb and am just curious.

Jason, Have a 2001 with the 8.1 and a 4:10 gear. On a pure highway shot - not towing - at best have seen about 13 mph. Have not checked it towing because I don't want to know! Wrink

I saw 10-11 mpg
8 towing 12K

w/ a Wester's ECM and a heavy foot. This truck would rock!

10-12 normal driving...

and the good news.. a whole 5 MPG towing roughly 12,000lbs...

Have a 2001 for sale fully loaded and then some!! yukon xl

2001 gmc dually,
13 to 14, empty
8 to 10 towing 38 ft donzi

2002 8.1 w/ 4spd Auto 4L85E in 2500 Avalanche (same as Sub 2500).
Lots of bolt on goodies.

11 daily driving.
6.5-8 towing 12K lbs, depending on flat Interstate or hills/mountains.

Thats about what my V-10 gets.

Oh yeah, 4.10 gears. I have 17" wheels and 265/70/17 E tires on it now. The Suburban will tow MUCH better with these changes:

Wider wheel/tire combo. (Go to an 8 or 9 inch wide wheel.)
Add rear airbags to help the rear suspension. (Do a search on this on OSO, lots of info.)
2" Rear wheel spacers. (Will spread out the rear wheel track to match the front wider stance, and also help towing stability.)

Everything IU have done to my Avalanche 2500, can be done to the Suburban 2500. (Exact same frame/running gear.) Check this thread for more info on what I have done:
http://www.offshoreonly.com/forums/s...d.php?t=109513