ok, got a 1992 Chevrolet K2500 P/U. Enginge is a 350. 4WD engages via the lever on the floor. 4WD was working fine the other day, but today took it up to snow line and just spun back tires. With the transfer case in 4HI I have no power to front axle. I looked under it while someone put it in 4HI and backed it up a bit. The front drive shaft is turning, as is the front axle on both sides. So, seems like it is in 4WD. But, when driving on pavement there is no normal tell-tale hard steering, chirping when turning, nothing. Also, took it into some gravel and punched the accelerator, back tires spun, front tires did not. Even got out again and looked underneath, front axle is turning when pulling forward. So, seems like it is in fact engaging 4WD, until you put it under a load, then there is no power to front axle. Does anyone have any idea what is wrong?