1998 GMC Truck not down shifting

1998 GMC TRUCK
88,000 MILES • V8 • 4WD • AUTOMATIC
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RHONDAM
  • MEMBER
  • 1 POST
can you please help- truck is not downshifting- from no gear. we have replaced the two shift solenoids and replaced fluid and filter. still will not down shift - have no 1st , 4th gear and no overdrive. when cold it shifts but when it warms up will not down shift.
Aug 29, 2009 at 4:06 PM
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MICKEY-D
  • ✓ASE Certified Mechanic
  • 304 POSTS
  • ASE Certified Mechanic
You never said what trans you have. If you have one that is a vacuum shift, you probably have a bad modulator valve. mickey-d
Feb 23, 2010 at 12:52 PM
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