Howling front end

Sometimes (love that it happens intermittently) when decelerating from highway speed for an off ramp, the front end will howl, pitch decreasing with road speed, not engine speed, until I get to about 5-10 mph - there is then a CLUNK that can be felt as well as heard and the howl goes away. It only does this after extended highway (at least an hour). I'm thinking TC or front axle and I don't want to start throwing parts at it until it's fixed - I'd like to diagnose this first. There is some slack in the driveline when accelerating from an rolling stop - a little, but not a lot

94 Jimmy 4x4 4.3

RF Wheel hub assembly is new, LF was ok but replaced axle seal. Diff fluid is new and full.

Please help!

EDIT: SORRY - I THOUGHT I WAS POSTING IN THE JIMMY FORUM - IF THE MODS COULD MOVE THIS, PLEASE!

Welcome to AF.
I do not think you are supposed tio drive on a dry payment in 4 wheel drive.
What kind of transfer case do you have?
Matched set of tires?
Does it howl to start with or after driving a hr. in 4 wheel drive?
Can you hear any noise in 2W drive?

Hear is a good link for rear end noises.
http://www.differentials.com/install.html

Welcome to AF.
I do not think you are supposed tio drive on a dry payment in 4 wheel drive.
What kind of transfer case do you have?
Matched set of tires?
Does it howl to start with or after driving a hr. in 4 wheel drive?
Can you hear any noise in 2W drive?

Hear is a good link for rear end noises.
http://www.differentials.com/install.html

Thanks for the prompt reply. This happens when I'm in 2wd. As far as what kind of transfer case, I'm unsure, but I have the pushbutton switch for 2wd/4hi/4lo if that helps. Yep - matched tires (all 4).

It's quiet while driving, accelerating, and cruising at 65 mph. When I start to decelerate after an extended drive (doesn't happen after 10-15 minutes on the freeway), the howling commences as described in my first post. Once it "clunks", the howl completely goes away and doesn't come back until the next time. It's very intermittent - sometimes it'll happen at least once in a 2 1/2 hour highway trip and then not at all for the next 4-5 times I make that same trip.

Some background - about a year and a half ago, I was in 4hi on an icy highway doing about 45-50 mph. The conditions cleared up after 45 minutes so I hit the switch to go back to 2wd. I "jogged" the throttle a couple times to get the transfer case to unload, the 4hi light went out and I accelerated to 65mph for another hour. When slowing on that trip, the howl occurred for the first time. It happened a couple more times sine then so I had the wheel hubs checked and replaced the rf hub assembly as the left was ok. It hadn't happend in about 6 months since the beaaring was replaced until the other day so I had assumed the rf bearing was the suspect.

Aparrently not.

Does it only do it in 4W drive?

Would a loose pinion bearing preload be affected by temp?

Does it only do it in 4W drive?

Nope - I only use 2wd on the highway - it was just that one time in extreme conditions.

Are you sure the front axel is unlocking good?
I would pull front drive shaft and try it with drive shaft out.
And check the front wheel bearing and front axel joints real close.
MT