I own a Jimmy and it is always slipping into overdrive (revs up to 3 on gage ) then it quits and drives normal- it does this alot , what is the issue - is it a speed or overdrive sensor - also gas gage was working fine and now its stuck on E with the low fuel light on - just filled it up so I know there is plenty of gas .
Overdrive on 1999 GMC Jimmy
by gumbie37 in Jeddo, MI on December 31, 2009
ANSWER by Oakman on December 31, 2009
You could be seeing the first signs of the transmission wearing out in your 1999 GMC Jimmy. It could be that a slight fluid leak in the forth gear apply circuit is causing 4th gear to slip on apply. I may be a good idea to have the powertrain control module scanned for fault to see if any transmission related fault codes are stored in the memory.