93 Dodge Dakota Looses power

Several years back we had the clutch replaced in my 93 Dodge Dakota 4wd,
since replacing it the truck had difficulty going into 4th, the mechanic that put
it in said it would align over time. but now it won't go into 4th at all, if you try it
smells like burning rubber. We are also starting to experience a sever drop in
power when pulling a trailer or even going up the slightest hill.  The truck has
147K, any ideas what could be wrong? Are the two symptoms related?  I will
not take it back to that mechanic.