Gas milage

[rrush]

My son has a 2000 5.4 the truck has a 8" lift and he is running 40 for the tires.He wants to lower it use 35" tires so he can get better mileage. No he get about 5 mpg. would he be better off and cheaper to change the gears in the front and back axles other than lowering it.
He got this truck already lifted so we do not have any stock suspicion does anyone out there have the stock suspicion that they want to sell.Thank you Roger
Sorry guys I was not thinking It is a 2000 F-250 manual trammy

[DarrenWS6]

That must be a huge truck! 40"s! I would have gone 37"s, might drive better. Depending what gear size he currently has would change its mileage. If it was the stock 3.55 or 3.73 gears then yeah that thing is really suffering, and must shift like crazy. 4.88s I would imagine it would need to be running with that height. If so, then the best alternative would be to down it to 6" with 35s.

[rrush]

Yes it a big truck I am 6 foot and I have to jump to get into it. I do not know what gears there are in it . But the speedometer reads the right speed. I would think if it had stock gear the big tires would make the speed be off.

[DarrenWS6]

Truck could have been tuned for the tires but theres a possibility it has bigger gears in it. A shop would have to do a check, or pull the differential cover and see. But lowering the lift would help some, getting rid of the monster 40s first would help. 6" lift with 35s is the highest lift & tire combo that can still get acceptional gas mileage.