Took my 98 4X4 Tacoma back to shop because of a metal tingling or scratching noise I was getting after driving the truck for an extended peiod of time. The only time I seem to hear this noise is when you left off the accelerator slightly while down a hill or slowing down. They said that person who had truck before had put the cover plate for clutch on backwards and they thought that was what was causing the noise. Well two days later it is back. Goes away when clutch is engaged and sound seems to be coming from underneath. Any ideas?

 

Did they try lubing the drive shaft and other parts of the drive train? That is a fairly common cause of the scratching/squealing under the truck.

 

The rusted out muffler in my truck sounds like scratching you are describing (down hills, decelerating). A 1998 sounds a little new for this, but I guess it would be worth a look.