GM-GMC: transmission, gmc 4x4, fades

Question
I have a 1991 gmc 4x4. When driving it sounds like the rpm's are at a constant rev.... never changing, unless i release the gas peddal then it goes down. As soon as i press the gas peddel it goes up. My temp gage is fine...doesnt overheat.  It just doesnt seem to kick into the next gear as i increase speed.

Do i need a new transmission or is it just the timing that needs to be reset?

Answer
Your description is a little brief however, if you are having no problems accelerating or reaching hiway speeds, it is unlikely that your transmission is bad or your timing is off.  What you are describing could be a faulty wheel bearing.  If the noise fades in and out when cornering or going around turns it could be a wheel bearing issue you have.