Awful thud while in 4WD
 

Driving home in Washington Beltway traffic the other day I noticed an alarming reoccurring issue that I thought was just a one time thing. I was in the middle of a torrential downpour courtesy of the latest hurricane or tropical storm or whatever that was hitting my area at the time, and decided to go into 4WD unlocked for some extra traction in the rain, to help me change lanes quicker and for extra grip around turns/ramps. What I noticed was a huge, and I mean huge, thud coming from the front of my truck after accelerating from 1st or 2nd gear. I would apply throttle, transmission would either already be in 1st or kick down to 1st without any hooplah, but then after releasing the go pedal, the truck would make a huge thud which would shake the entire truck as if I had just gone over a large pothole. Any ideas on what could be causing this?

tranny switch only in four wheel could be the front transfer case just ideas

Ya think it could be your axles binding up due to the fact that you still had a fair amount of traction even in the rain? Try making a turn on dry pavement in 4WD and see if it is the same feeling.

BTW...if you're going too fast around a curve to spin out in 2WD, then you're probably going too damn fast to begin with. :nerd:

I don't think it was any binding since I only pushed the 4WD button, essentially giving me AWD. I drive an '02. The only binding I have ever experienced has been limited to exiting a beach road and turning onto solid pavement while in 4WD with the center differential locked. Only in mud/sand/sometimes snow do I drive with the center differential locked.

And to your second point - the TRAC/VSC system in my particular year is extremely finnicky and overly-sensitive. There was enough standing water on the road to drown in...(take this for what it's worth, you can drown in 2 inches of water, but you get the point)...and my rear wheels were losing traction frequently. When the rear wheels lose traction, thanks to the wonders of VSC, power is cut to them, leaving me with my foot to the floor but making no forward progress. I engaged the 4WD/AWD/whatever you want to call it to lessen the chance of myself sitting in the middle of a lane change with no power.

I would check your axles and diff. . also how good is the tread on your rear tires? (just have to know if you kept hydro-planing)

I'm taking it into the dealer tomorrow to have them check it out. I have a little more than 30k on all four tires, I'd guess that there's maybe 50-60% tread left. Had them installed in December '08. Yikes I just realized I've driven over 30k in less than a year.

All your tires the same tread depth?

Yeah they are all evenly worn. Turns out there were some metal shavings in the transfer case... which does not sound like good news. I'll post up more information in a couple days.

yup metal shavings = bad things, the reason why I want to find some magnetic drain plugs for my ride since they save you ass in the end (gives you early warning of something is grinding)