Question about Chevrolet C1500

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1995 chey truck 4x4. 150k miles. transmission shifts good but around 45-50 mph I believe transmission is shifting in and out of overdrive. Rpm is constantly changing. What coud this be?

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  • waynehester1 Mar 14, 2011

    Thanks.. are these parts available at local auto parts or need to be special ordered?

  • waynehester1 Mar 14, 2011

    Did you get my follow up question?

  • waynehester1 Mar 14, 2011

    one final question.... what is transx? Is this a special brand of transmission treatment? thanks

  • waynehester1 Mar 14, 2011

    Thanks johnjnail. I will try the things that you reccomended. Maybe it will save me a transmission job...

  • waynehester1 Mar 18, 2011

    Will taking the bottom off to service the transmission allow me to install the other things that you reccommended.... thanks


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Probably not overdrive, most likely the lock up toque converter, most likely a trany. service will cure the problem, but wile you are in the transmission changing the filter you could replace the lock up converter switch just in case it might be going bad, also when you refill the unit put a quart of transX in with the new fluid, its like miracle juice in a can, the best thing i can tell you about the switch is to buy one there not that expensive less the $30 that way when you remove the pan you will know what to look for. i guess the best way to know if its the lock up converter or overdrive is the amount of the RPM change under 400 RPM change its the converter over 400RPM then its 4th gear in either case the first action to take is the transmission service, also there is a 4th gear switch inside the pan as well. if it turns out to be 4th gear dropping out replace that switch also, if the service and switches do not cure the problem then you are looking at a new transmission.

but i am pretty confident that the service will cure it.

let me know if there is any thing else i can do for you.

Posted on Mar 14, 2011

  • 2 more comments 
  • john nail
    john nail Mar 14, 2011

    with the age you might have to order them but NAPA has next day service on most parts, they used to keep them in stock but it has been a few years.

  • john nail
    john nail Mar 14, 2011

    when at NAPA ask them for a quart of transX, it is a automatic transmission addative, and like i said it is like miracle juice, it is a very good cleaner/lube.

  • john nail
    john nail Mar 14, 2011

    good luck.....thanks for using fixya

  • john nail
    john nail Mar 18, 2011

    yes, you may have to remove the valve body to get to the 4th gear silnoid/switch but it is not that hard, just take your time, you are not in a race.....good luck


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