when I engage the 4x4 (electric ) there is a gear clashing sound when I try to drive. I can hear the transfer case shift into 4 lo 0r 4 hi and I can feel a bit of a clunk when it goes into gear but it seems to slip on the gears when I drive. The over drive also makes a rattling sound when it shifts into overdrive when under some throttle load but stops when I ease up on the throttle. Overdrive will quit working and go to 3rd.if I keep on with the throttle down and the engine light will comes on . After sitting for a bit it will work again but will still persist with the rattling especially if I am pulling something like a trailer with a bit of weight on. any thoughts on these problems ? Gerald m