1996 GMC Jimmy Transmission issue? No overdrive

REDTAILDOVE

MEMBER
1996 GMC JIMMY
4.3L
V6
4WD
AUTOMATIC
150,000 MILES

I have a 1996 gmc jimmy with aprox 150000 miles on it. I noticed it wasn't shifting into overdrive and the rpms were not dropping to where they usually do after OD kicks in and the check engine light came on throwing a p1870 code. My mechanic changed the trans filter cleared the code and sent me on my way. Still no overdrive. He suggested maybe a speed sensor.I would prefer not to guess at this point. The truck shifts flawlessly in all gears, just no overdrive. Anyone have any suggestions?

Wednesday, May 27th, 2015 AT 8:27 AM

1 Reply

HMAC300

MECHANIC
48,601 POSTS

Code 1870 is the trans is slipping so have a trans guy look at it. There is also a tsb on this although it may not pertain to your vehicle there are wiring thing s that need to be changed so you don't have the problem again. I'm sure the trans guy is aware of it. You have probably burnt out one of the clutch paks.

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Wednesday, May 27th, 2015 AT 9:45 AM