1988 300zx
 

My z will not shift into overdrive sometimes. Sometimes it will shift into overdrive and then drop back causing high revs. Fluid is clean. Somebody
told me it could be temperature sensor?? Any help??

when your trying to go into overdrive, does it just keep reving and reving and just wont shift, or if not, what happens?

1988 300zx
 

It just keeps reving. It would normally shift at about 2300rpm, but when
it doesn't I've taken it past 3000rpm and it won't shift.