I just bought a 1999 Dode Ram 1500 Sport. When i put it in 4 high or 4 low it will engage and the light comes on. However, when I drive the light will go out for a few seconds then come back on and I feel it jerk as if it were engaging again. It continues this on off pattern until I take it out of 4 wheel drive. I'm guessing some sort of vaccum problem. Any suggetstions? I'm trying not to spend $100 an hour and fix it myself if possible. Any help is greatly appreciated

 

It's not fully engaged. Put the tranny in N, then shift into 4H, then put the tranny in R, go back a few feet, then in D and go and see if it does it after that.

 

It is a problem with your CAD unit. Search on here, it's asked about 2 or 3 times a day.