tranny problem?
 

I had my tranny replaced on my 99 jimmy, 4.3, push button with auto 4x4 about 3 months ago. Now when I get to about 30 mph, I hear a slight whine type of noise. I'm thinking its a tranny issue because if I cost down a big hill going 30, there is no noise. Wouldn't a hub still make a noise regardless of if there is torque or not?

Bump, the noise is more of a humm

I've heard that plaid is a good tranny repellant for your whiny tranny problem. Wait... You're talking about your truck. Gotcha. Are you positive that the sound is from your transmission and not something else like U-joints? It could also be the front differential not totally disengaging or engaging if you've shifted. That turned out to be my problem: My front diff wouldn't totally disengage for a while and had a growling sound until I could get it to kick out.

Good luck. External sounds are really hard to track down.

Lol guess I should have been a bit more precise in the thread title. I thought that as well about the front engaging but I tried it in 4x4 and its still making the humm. I'm about to throw on new u joints to see if that helps. What did you end up doing on yours? Thanks for the reply!

My problems ended up being either the driver's side CV (most likely as it was quite sloppy when I got it out) or internal to the front diff. I replaced them both at the same time as part of upgrading from 3.42 gears to 3.73, so I can't say absolutely difinitively that it was the CV.