At least I think it's the transmission. When ever I'm in low gear, I hear it, and as it revs higher, the noise eventually goes away. I've heard this could mean I need to check the fluid level, or that something is wrong?

 

did you.......check the fluid level?

 

Check your rear differential fluid also. If the fluid gets low it can whine.

 

I don't know how to check it. Is it like a dip stick under the hood?

 

The transmission fluid does have a dipstick under the hood. On your ear diff you will see a seal/plug. Pull it out and see if the fluid is up to the top. If its not, fill it up and look for leaks.

 

but it only does it in low (1st) gear? So when it shifts to 2nd, the sound goes away?

 

My first gear whines a bit if I downshift while coming to a stop. It doesnt whine any other time including accelerating or in 2nd gear.

 

check the fluids...for the trany...start the truck put it in neutral when you check the transmission!

 

It all depends on how often you drive it. If it sits awhile then your going to get that, it even states it in the owners manual.

 

Yes sir.