How do you tighten or adjust the diffs on the 18T? Mine made a sound like it ripped out all the gears so I tore it apart and none of the gears in front or back were stripped. I re-assembled it and it's fine now but the front wheel drive doesn't seem to work, it's just rear wheel drive now basically???

sounds like you got more than a diff problem, you sure all the axles are back in place after the re-assembly ? to do the diffs, you remove one of the axles, i forget what side, and put the small allen in the cup to tighten or loosen the screw inside, but the stock ones really suck, its just threaded into plastic, the mip diffs are really nice !! they use metal, just like the big brother 1/10 scale trucks.

Yea all the dogbone axles are back in place and seem to be operating correctly but the 4 wheel drive is not working very well. I found the diff adjusters on the passenger side of the truck, I held the drivers side wheels and tightened the diff screw a little but it didn't make much difference. How tight should it be?

didn't you get a manual for that thing?

more than tight enough that when you spin 1 tire all go in the same direction with the motor in

yeah, the diff should be tight enough that when you spin 1 tire all go in the same direction with the motor as David18t said, but if that dont work just take it back apart, and look at the manual and see if everything is where it goes, Also when it happen did you hit a wall or curb or jumped it off something????? let me know
Hope this helps,
CD