Possible transmission slip?

[torumekian]

ok, basic info, 98 4.0 sohc v6, automatic trans. 252k miles, original engine and transmission. no previous transmission work needed other than flushing.
this morning i was on my way to work driving down the freeway and everything was normal. once i got on the freeway and i needed to drop a few mph i let off the gas to coast to drop speed. once the rpms dropped down and i started to slow, my car started to sound almost as if i was driving an old car with a stick and tried to shift into a lower gear but my rpm was too high. now it was exactly like that, it didnt feel like a grind, there was no vibration. but kind of sounded like one. i know thats a funky explanation but its hard to describe. ive done light work on cars for like 15 years now and not heard anything quite like it. but it didnt feel like i was out of gear. when i re-accelerated it went away and drove normal. when i let back off the gas again, it happened again. in order to feel like i wasnt going to be stranded i ever so lightly left my foot on the gas just enough to not allow it to make that noise and used my left foot to brake. as soon as i got off the freeway it stopped. anyone experienced this or know what it might be?

 

[Donald P]

Could be the valve body gaskets. Not a huge problem to change but a messy job.

 

[drdoom]

Transfer case. What you hear is the range slider AKA HIGH/LOW collar coming out of engagement with the main shaft. It is grinding the teeth. You need to rebuild and upgrade the case.

 

[IZwack]

I'd say its probably more of a transmission issue than a t-case issue as a t-case engagement between LO and HI range on the highway will cause a sudden surge in the vehicle and will definitely at the very least cause a loud clunk.

 

[torumekian]

ok so i filmed it. its of course a crappy phone video. i will upload the video and post a link. for a few additional details that i noted when driving home. it happens every single time i let off the gas above 45 mph. and it doesnt start happening till about 2k rpms. it also happened on my way to the hospital today (to deliver my second baby) when i was backing out of the driveway. not at a set RPM, but as soon as i put it in reverse it happened. i shift back into neutral, then back into reverse and it didnt happen again.