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Chevy 3500 transmission not upshifting

Discussion in 'Chevy Trucks' started by faughtj, Jan 24, 2004.

  1. faughtj

    faughtj Member
    from NE Ohio
    Messages: 46

    I'm new to this board, but have gotten lots of useful information that I greatly appreciate. I have a 95 Chevy 3500 4x4, with a dump bed, 6.5L diesel & 4-spd auto transmission & 8' Western Unimount plow. My problem is the transmission will not upshift like normal. It will go into reverse and forward, but when you get to 20 or so and it would normally upshift, it just hangs and will not go further. It was fine a couple of days ago, then yesterday the weather was near 0, so I had a battery charger hooked up as the battery was weak. Got the truck started, and plowed this morning with it. But, it seems like it's stuck in 2nd gear.. I'm wondering if this is some sort of electrical or computer problem rather than a transmission problem since it goes F & R with no problem. You can't really go faster than about 30 or it really sounds like it's working.. being a diesel it redlines @ 3500 rpm anyways. The truck has about 104K miles and I'm wondering if anyone has any ideas, so if I have to take it in, at least I have an idea of what's wrong so I don't get broadsided with a trans. rebuild when it might be something simple.
  2. parrothead

    parrothead Senior Member
    Messages: 157

    i've got an 02 3500 and had the same problem, it was a switch on the side of the transmission. i would check with gm and see if they have one or if this is the problem, good luck
  3. S-10 Plower

    S-10 Plower Senior Member
    Messages: 104

    i had a problem like that on my s-10 with 105k on it. it did the same thing at 45mph turns out the trannys go out around 90-110k. I had blown out 3rd and 4th gear.

    Good luck

  4. Firebrands

    Firebrands Junior Member
    Messages: 23

    My '95 2500 did the same thing a few weeks ago. The short term remedy I found for mine was to disconnect the battery for a few minutes and then hook it back up. My transmission would then shift correctly. The shop I go to diagnosed it as a wiring harness/solenoid problem. Cost me $450 for them to replace the wiring harness and solenoids from the pan. So far so good, now if I could just figure out what all the other clicks and whirrs are.
  5. faughtj

    faughtj Member
    from NE Ohio
    Messages: 46

    Thanks alot for all your help.. I suspected it was electronic since the trans. was rebuilt less than a year ago. Took it into my local shop and the ECM was "scrambled". They cleared all codes and works great now. I guess I should've done that myself but was afraid of screwing anything up any worse than it was.