Posted by AJ on January 15, 03 at 04:47:00:
In Reply to: 4.10 rear to 3.73 or 3.42? would it greatly improve gas mileage with 8.1l? posted by Joe on January 14, 03 at 17:19:09:
I have an '01 2500 8.1L w/ 3.73. I too am heavy footed and get 10-11mpg normal driving (lots of stop&go). I get about 12mpg highway. I have a stone/bug shield which supposedly costs 1mpg (I would rather avoid damage to hood). When I tow 4,000# boat, I get 10mpg, with power to spare. Added Hypertech programming which improved acceleration, and marginally improved mileage (got closer to 9mpg towing before programming). I use 93 octane, and change oil at 3,000 miles.
I guess I'm lucky; 35,000 miles and no evidence of piston slap. It did burn oil early on, but stopped after about 20,000 miles.
Personally, I don't think you'll get much mpg improvement with 3.73. And if truck is 4x4 you need to change both diffs. I believe the job would cost about $1,500 (less if you do it yourself/find used parts). At $1,500, if you got 1.5mpg better, it would take 75,000 miles just to break even. The 8.1L has a very broadpower band, and the 10% difference in RPM doesn't change performance enough at speed. The 4.10 probably has better pull off the line. I would consider other enhancements first, like programming the computer, better breathing exhaust (although earlier posts regarding research by Gale Banks, indicate the 8.1 is tough to improve below 4,000rpm).
Good luck.
:I have a 2002 yukon xl 3/4 ton with the 8.1L engine and 4.10 rear end. I,m getting around 10 miles to the gallon around town and 12 on the highway. I do have a very heavy foot, (can't help it). I tired of having to re-fuel every 3 to 4 days.. Thinking about changing rear end to improve mpg. Does anyone have any experience with this? Wondering what kind of improvement I might see and would it be worth it. My last suburban was a 99 with 5.7, used to get around 17 mpg with it. Tow wise, I pull a 2600 lb trailer (enclosed trailer with 2 atv's, and plan on getting boat later this summer apx 6000lb) This truck has plenty of torque with the 4.10, I'm thinking that there would be enough left over to pull 6500lb if I make change.
: This Truck also has the piston slap and possible the oil usage problem. Any suggestions?
: Thanks,
: Joe