hey guys. I haven't posted in a while. 4 kids later and a couple moves around the world things have finally settled down a bit.

I'm getting this very weird loud almost spooling like sound (whining, spinning sound) when i'm decelerating or taking my foot of the gas. it happens in all gears and at all speeds. it's almost like when my engine goes into a "deep" vacuum it starts making that spooling/spinning sound. I've checked all the connections, nothing is loose, no CEL, nothing obvious under the hood or under the truck. Specs of the truck in my sig

it happened when i was driving down a mountain. i was coasting down the mountain and in vacuum for a couple seconds, then all of a sudden i started to hear a loud spooling/spinning sound coming from the engine compartment. this has never happened before, and i've never experienced it in any of my vehicles.


Any help would be great.i'll try to paste a link to a video i captured when it happens. you can watch the RPM meter drop, then all of a sudden you hear the sound. If i give it a little gas, it goes away immediately, pause a second and it comes back on decelerate.you can hear it from seconds 7-11 then 13- 16, and again from 22-24. you'll notice that the sound doesn't really start until about 2 - 3 seconds after i take my foot off the gas

here's the link:
i thought it was the bypass actuator for the supercharger. I ordered a new one from Magnuson, but i installed it and the sound it still there. so $220 dollars later, the problem still exists.

however, i did notice by chance when i put the truck in 4WD that the sound goes away completely. just to double check i coasted down a hill in 4WD no sound, put in 4wd and the sound immediately came back. so i'm guessing Transfer Case... maybe front Diff?

 

Front diff. Its most likely a pinion bearing. They sound like that when u take the load off of it and it free spins. Basicly the same thing as accelerating and coasting.

Grab the front diff yoke and check for movement. Check u joints as well.

 

So you're saying that loud spooling/spinning sound is the front diff "free spinning"? why can i only hear it in 2WD and not 4WD?

i checked both drive shafts. absolutely no play in the rear shaft at the rear diff or the transfer case. the front drive shaft had no play at the front diff. BUT, it did have some play where it connected to the transfer case. is that the problem?

thoughts?

 

i pulled the transfer case fluid and it looked perfect, no metal shavings at all. the front diff looked a lot different. this is what i saw. is this abnormal?

 

yes

that girl needs some service for sure