I have a 1987 Jimmy Full size. At low speeds around 5-10 mph while in drive, there is a loud clunk that continues till I stop. Once I exceed 10mph the clunk goes away. I assume that the problem is in the transfer case. If I move the lever down, the clunking stops. Is this a linkage problem? If so, is this fairly easy to fix? The Haynes manual seems pretty easy to follow but I want to make sure thsi is the problem before I start tonight. Thanks for the help!!