something's wrong...
 

I've noticed when I'm going along in my truck that when I get to 3rd gear and I'm going about 25-30 mph, I feel this shudder. My first thought was U-joint. Or at least that's what I suspect it is. I also thought it could be a tire out of round, or a warped rotor or something. This is a constant shudder that goes...bump,bump,bump,bump......and I only notice it in 3rd gear while going about 25-30 mph. And I can barely feel the vibration through the gas pedal with my foot on it. Brakes work fine. The tranny shifts perfect. My truck has only 30k miles. This has me stumped. Any help is appreciated. Thanks for listening. :help:

but you don't feel this if you are going faster?
it only happens in that speed range?

No only in that speed range. It feels very smooth after it gets to 35-40 mph or higher.

Tire balance???

I just noticed something when I crawled under my truck just now. Right where the engine and tranny connect, there is a thin metal gasket in between the two. And on the tranny side, there is about a 6 inch long thin gap at the front of the tranny at the bottom. I noticed in this small gap that there is some fluid of some kind leaking out onto the thin metal gasket I was talking about. I smelled it, but it had no smell. It's not a bad leak, just enough to cover a 3 or 4 inch area at the bottom of the trans on the side closest to the oil pan. Looked like a mixtrure of carbon and water or something. I have seen this on other trucks I've owned too. Is this normal? Is that little gap there for a reason?

Changed tranny fluid. Problem solved.;)