I have a 2004.5 LLY In low range the throttle is responsive when in park, reverse, and nuetral but not in the forward gears. You can hold the brake and put the pedal to the floor and back up and it will do nothing. If you hold it there for about 2 seconds it will rev up slowly but the most you can get is 1500 RPM untill you start moving. High range is ok. Tried a new truck at the dealer and it did the same thing. I need more rpms when taking off when sled pulling. Are there any fixes for this. Thanks for any comments.

All trucks will do this. If I am thinking correctly, GM did this so there wasn't so much torque sent through the drivetrain. Just think of the power you have in 2wd and now you have just doubled???? it by going into low range. I am sure that there is a more technical answer but that is how I know to explain it.

Thats called the torque management system, like stated above if you had 100% full power in low range, bye bye running gear! also these fuel systems work off of boost and in low range theres hardly any load on the motor to make boost so there isnt alot of fuel being sent through the injectors. As for putting the brakes on in low range, usually if the computer sees boost (your now making a load on the motor and making boost) but doesnt see vehicle speed then it will also defuel the engine through the TMS.

Mine does not do this..I yanked a stump the other day in lowand I eased the clutch out and got intot he fuel..it spun all 4 tires...LOL

Ditto, mine doesnt either as I truck pull in 4 low and it gets just as much fuel as it does in 4hi.