Help! -Mystery Clunk

[LeachLaker]

Any help appreciated!

I have a 1998 V6 SOHC 4x4 Explorer with 90 some thousand miles on it. Last fall we started noticing a hard CLUNK on inclines. It sounded like it was shifting into 4 wheel drive and had a metal to metal sound. It was infrequen, occuring every few days.
The clunk became more frequent to the point in occurs once a minute.
We took it to a mechanic and a tranny guy and neither could diagnose it. Took it back to the tranny guy who has been trying different things for a couple weeks.

These are the facts:

-Does not happen in 1st.
-Transmission shifting sounds healthy and normal.
-Mechanic and tranny guy found no broken or loose parts
-Neither could get the clunk to 'clunk' while on a lift
-Used to happen mainly on inclines, now it happens on inclines and flat,
but not declines.
-4 wheel drive is the original, push button. It still works when manually
engaged.
-As the clunk has increased in frequency, it has diminished in it's jarring
power.
-Turning corners does not trigger it.
-Tranny guy says 4 wheel drive, tranny, drive train, tran case all look
good.

Has anyone experienced this?!
Any Help Appreciated!!!!!!!!!!!!!!!

 

[97sprt4x4]

have you looked at the front axles/diff/hubs? almost sounds like something in the front end is going.

Justin

 

[LeachLaker]

Yeah - my novice self saw nothing obvious. Mechanic saw nothing. Tranny guy said they are all good.

Thanks for reply