So today is the first time I really got to drive in the snow with my xterra and drove from my place to work in 4WD because the ground was covered. On my way back home, I noticed that when my truck is in 4th and 5th gear (automatic BTW) and I let of the gas long enough to let the engine brake and then give it gas again it makes a audible "clunk" that you can feel. It feels like there is slack in the driveline. This ONLY happens when I'm going about 40mph or slower and it's in 4th or 5th gear. I downshifted into D3 and it does not do it. This "clunk" won't happen above 45-50mph.

Torque Converter lockup is only in 5th gear right?

I kinda have a theory, that the truck is shifting into to high of a gear at too low a speed.

Here's another odd thing too, not sure if it is related. When I started the truck this morning it was making a strange "whining" sound from what sounded like the driver side under the hood or tire area. Sounded like the kind of whine if you combine the sound of a weak electric motor and a power steering pump at full lock turn. It would do it intermittently but only in park (i think).

I appreciate any input! Thanks.

I'll also have to see if this continues tomorrow.

I think it may have been a computer problem. When I started to drive off the truck slid and I spun the tires when it was still cold, which is when the computer is still kinda calibrating for that drive. So maybe I confused the computer?

That's the only thing that makes sense now because once I got home I let it sit for about 2 hours, then I went out for a drive and it wasn't doing it anymore.

Is the Torque converter lockup electronic or mechanical?

It's electronic and can apply in 3-4 & 5 grears

So I guess that explains why I feel "half shifts" in those gears, although I expect the one in 5th. Ok, cool, didn't know that. This is my first automatic tranny ever.

So along the lines of the original problem maybe I tricked the computer that day and the TC was staying locked up in those gears or something. Reason I say that is because when that "clunk" happened it felt like it was "direct drive" if you know what I'm trying to say.

Didn't happen all day yesterday, but thanks Bass4Runner your input was very helpful and it appears you have helped me diagnose what happened.

hasn't been doing it now for a day? I think I just pissed off the computer and it was locking the torque converter at weird times. Hopefully it doesn't do it any more. It wasn't really LOUD but you felt it more than you heard it.

When I was out doing some donuts in 4wd in the snow I thought I heard a what sounded like a quick gear grind sound, but when the tires are spinning and your spitting up snow into the wheel well it kinda sounds like a bad shift with a manual tranny. If I did in fact break something I think I would have noticed something while driving around after that. blown diff would have locked up or tranny wouldn't work right if something broke. So whatever, seems fine.