Clutch or Transmission

I wouldn't expect a clutch problem to only affect 3rd and 4th gears. Either the clutch is slipping or it isn't. Has the trans fluid been changed? If not, I'd do that first. You might consider replacing the fluid with a synthetic. Good luck. Al

If a clutch is starting to slip, you will notice it in the higher gears first. There isn't as much torque against the clutch (usually) in the lower gears.

GC

I'd definably second the changing of fluids... it does wonders for an old tranny in my experience. just make sure that you get the correct fluid for your tranny otherwise it isn't realy going to help also you could find that your sycro's are going but i dunno if thats as much of a problem on the newer toyota trucks or not

While trying to get the transmission fluid checked this weekend the mechanic stripped the fill plug head.

Guess I have to live with the problem till I get rid of the truck or something goes out completely?

Head or thread? If its the head go buy a new one for $4! If its the thread, get the dopey bastard to replace the unit or fix it!

even if it is the threads just yank your tranny and throw it on the workbench... take a drill to it and install a heli coil or retap it by hand... (a heli coil will be stronger then original as long as you do it right) you could also try various thread repair compounds and such... although i've had good luck with heli coils

Stuff that!! If someone else did it let them fix it!