[amigo-2k]

It could be something as simple as the fluid is low in the tranny.

These trannies like frequent fluid changes (~30K) or they can get grumpy. you can find used trannies for 1k and new cost3.5K (more then your truck is worth).

So I would start with having the fluid topped off. If that doesn't help, I'm guessing the tranny needs a rebuild, or replaced with a lower mileage one.

Fuel gauge. It is a 40 dollar part that is in the gas tank that is causing it. The tank has to be dropped to replace the bad part.

Also, autozone will read CEL codes for free. The codes will point you in the right direction as to what is wrong with the truck.