Lately I have been having trouble shifting while driving my 3 tree 54 1/2 ton. While driving along I'll suddenly have trouble getting the clutch fully engaged in any gear. The gears whine and when clutch is disengaged the truck won't coast as you'd think it should, like it wasn't free. I'd smell transmission fluid while it is in gear and whining. Eventually I can get it working fine in all gears and it will work fine but I never know when it will get stuck again. Does this seem like a linkage adjustment issue? Clutch going out? I appreciate any ideas on what the problem is and how to fix it. Thanks much! Steve