My 2000 SR5 4WD has developed a very disturbing behavior. It has a CDL button on the dash (left of the steering wheel), but I've never used it or really tested it out at all.

The truck is being used by my daughter @ college in western NC. She has been shifting between H2 and H4 this past winter as the conditions there have changed from snow/ice to dry surfaces and back to snow/ice. (This truck does not have the automatic 4WD button on the side of the 4WD shifter because it is an SR5 not Limited.) She has not used the CDL button at all, and I'm pretty sure it is OFF.

What happens is that when she puts the truck in Drive, the transmission will drop into gear, but when she presses on the gas pedal, it doesn't move until the rpms get up to about 1500 then something "pops" and it will lunge forward. Even when moving forward it seems like there is resistance. Also will do this in Reverse.

I visited her this weekend and verified this strange behavior. I checked the shifting from 2WD to 4WD and it doesn't always disengage the front driveshaft when in the 2WD position (and the green 4-wheel symbol on the dash will stay lit).

Is my center diff blown?