i have a chance to buy a 89 xtracab sr5 pickup the truck is relly nice it has 250000 mi. i love the truck but it has a problem with the transer case the truck has full time 4 wheel drive when driving it shifts into 2wheel at like 35mph then when slowing down the thing goes to kick back in it whines then clunks into gear. the truck is only $900 and i was wondering if this is fixable or how hard it is to change a t-case or if i should beware of this deal.