I have a 2000 GMC Sierra 1/2 ton extended cab 4X4. 3 years ago I put a 6" lift on it with 35X12.50X17 tires. To try to gain some of the lost torque back I did the following mods:

K&N cold air induction
Air RAID throttle body spacer
Dynatech SuperMaxx LT headers, hi flow Y pipe, high flow cats
Gibson cat back exhaust
Hypertech power programmer

The truck runs OK, but the tailpipes are very black and I get terrible mileage. I get pretty much 10-11 mpg no matter what; In town, highway, towing, etc.
Would I benefit from getting the truck dyno tuned? If so, how much HP and TQ? Would my mileage improve? Lastly I live in east central Iowa. I believe the closest tuner is in Chicago. Are there any closer? Thanks for the help!!!

Scott

 

A tune might help. I would suggest putting in some gears. It's taking more power to turn those bigger tires. Also, now that you are lifted there is going to be more wind resistance. The truck is bigger so now there is more surface area. You have to remember that when you lift it your mpg is going to go down.

 

Get smaller tires, drop down to a 3" to 4" inch lift, get some lower gears, and get it dyno-tuned. Then you should get back all your torque, plus some.

 

park the truck and only drive it when you have to, with all the money you'll be saving on gas you can afford to buy an ls1 f-body. problem solved!!!!!!

 

Get front and rear gears. What gears are in it now, the ratio?
I don't see much really to help low end power, looks like all the mods you've done will take a little low end away and add a little to the top end.

Right now your engine is lugging, put the right gears in it and it most likely will increase MPG because the engine won't be bogged down.

I did this to a 4x4 once, went from 3.42's to 4.56's, with the 35x14.50's I put on it the 4.56's brought the cruise rpm back to stock, made the truck feel more powerful, etc.

 

Yea, gears are in the near future plans. It has 3:73's in it now and I am going to go to 4:56's or 4:88's in it. As far as the F-body, a deal is in the works to trade my '68 Camaro for a '98 TA WS6. But knowing how I drive my Camaro, I don't think the TA will get much better MPG's!! Thanks for your input.

Scott

 

yeah lifted, big tire, 4X4s dont tend to get very good mileage.