Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello I will help you with your question,
The lower numbers will give you better mileage but you reach a point that the engien does not have enough power to move the vehicle and it feels very slow. I would not go more than the 3:42. Unless you have free parts and are doing the work yourself you are not going to get your money back in fuel savings. Any gear change has to be done to both the rear and the front on a 4x4.
If you really want better mileage it would be better to sell the truck and move to a 2x4 with as light a weight as possible.
Please let me know how I can help you with this
I am always glad to help, please let me know if you have further questions