GMC W3500 cabover

Discussion in 'Mechanic and Repair' started by caseysmowing, May 24, 2013.

  1. 20/20

    20/20 LawnSite Member
    Posts: 164

    Would it be a chevy 350 or would it be under isuzu npr. I realize the engine would be the same but???????????????? I have the chevy but when I need parts I look up isuzu npr, much easier.
     
  2. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,898

    Took it to advance but no luck on checking codes. They don't have NPR in their system either. Change the oil and transmission fluid but haven't taken it out yet. I have another place to try and run some codes.
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  3. Bashby

    Bashby LawnSite Senior Member
    Posts: 446

    It is probably the vehicle speed sensor, you could just try replacing it if you have no luck with codes.
     
  4. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,898

    Have no idea where that is located any help would be great. How much for the speed sensor?
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  5. Bashby

    Bashby LawnSite Senior Member
    Posts: 446

    They are generally located toward the rear of the transmission where they can get a reading from the output shaft, some older stuff used the one in the rear end. If you get one to look at It may be easy to find. They may even call it an output speed sensor. It may be a dealer item only.
     
  6. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,898

    Took it out yesterday and it ran fine. The speedometer did act up just a little. It never moved more than 5mph faster than what I was going. When it happened before it was like 20mph. Sound like a speed sensor?
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  7. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,898

    Ordered the sensors. There is a input and output sensor. I just ordered both and putting them in this weekend. If this fixes it on to the ramps. Can't get anything done this summer with all the rain and extra work.
     
  8. caseysmowing

    caseysmowing LawnSite Bronze Member
    Posts: 1,898

    Sensors didn't work:(! Seems like when you get on it when it's in 3rd & 4th is the only time it does it. Never did it when I test drove it. But a 100 miles in to me owning it it starts. Any other suggestions?
     
  9. DaveOhio

    DaveOhio LawnSite Member
    Posts: 30

    It sounds to me like it may be time to establish a relationship with a truck mechanic. An auto zone isn't going to help with a commercial truck.

    Hopefully they can diagnose w/o a teardown. Good luck with it.
     
  10. 123hotdog

    123hotdog LawnSite Senior Member
    Posts: 482

    Casey, I have an older truck. A 1993. I struggled for two years looking for somebody to work on it. I wasted a ton of money on idiots. I would call Don @ Team Tire in Waynesboro. I would ask him if he knows somebody that specializes in box trucks and cab overs. I hope this is the only trouble you have with it, but if not you really need somebody that works on these trucks specifically. I would ask around at the truck stop between Staunton and Lexington. We have a free service tire store franchise here which is like a regular tire store but they have a truck center that only works on one ton and larger trucks. They usually fix mine in one day. No down time. I love it. Best of luck.
     

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