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  1. #1

    Default 1985 S-15 Shift speeds?

    I've just purchased a 1985 GMC S-15 pick-up from a neighbor...says it has a freshly rebuilt engine and transmission, 2.8 litre automatic....Im not sure the transmission is shifting properly...all is good until I reach about 5000 rpm, and she just doesn't seem to want to shift into overdrive....It's like Im driving around town at 5000 rpm all the time...She will shift on into overdrive at about 67 mph, which seem high to me...downshifts to previous gear at 54 mph....Is this normal for the S15? Or should I have it adjusted, and is this something I can do?

  2. #2


    First 70 mile drive to work today, she seems to be shifting okay now, around 55 mph, depending on grade...She'll downshift around 58 going up a slight grade on the interstate....Still would like to see a shift into overdrive a little sooner....

  3. #3


    Taking truck to AAMCO tomorrow...manager says he's familiar with the truck and transmission, says the valve body either needs repair, or replacement...maximum cost worst case scenario is $375, guaranteed fix.....previous owner (seller) says he'll pay half the repair bill for me....

  4. #4


    Located TSS sensor after O'Reilly auto parts showed me a picture of it, attached a vacuum hose that actually had suction on it to the sensor, transmission shifting perfect now, goes into 4th or overdrive at 45 mph, and cruises on the interstate at 70 mph! TSS sensor HAS to be connected with good vacuum for this transmission to shift properly, contrary to what I've been told by 2 separate people.....

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