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  • Speedo jump

    Hi guys, new member here....I need some genuine thoughtful input. I love this car and I'm dedicated to it till I use it up. I have an issue that needs to eradicated and I don't know what else I can do. It's one of the these problems that occurs when only when I'm on it, in that regard dealing with a repair shop is just way more trouble than is worth.

    This is a 2018 Camaro 1LS V6 6-Speed manual with 77k. I've owned this since new.

    This problem started at about 45k miles and it hasn't become any worse, I've been learning to drive around it. My problem is when I'm rolling the tach up high, say 4000+, and I stay in that upper RPM band screaming away, I'll up shift and then after that my speedometer starts flapping around +- 5-10 mph, bad enough to trip the "Reduce Clutch Use" warning. The problem will reliably occur after a No-Lift Shift.

    -The problem is rectified if I shut the engine down and restart.-

    These are the facts-
    1.) My clutch is not slipping, my clutch holds and holds tight. I REPEAT! THE CLUTCH IS NOT SLIPPING, THE CLUTCH IS HOLDING TIGHT. Do not tell me its slipping. If you would be so kind to spare me that shit, thank you.

    2.) When the speedometer is erratic, it will take the cruise control with it. With that said, no other systems seem to be affected...

    3.) The speedometer reading out of the ecm does reflect the speedometer reading on the dash. So I've ruled out the cluster and the BCM...

    4.) Re torqued all engine and battery grounds, no change.

    5.) Speed sensor has been replaced with GM new, no change.

    6.) Had a spare ECM programmed and installed, no change. I do intend to tune engine at some point so I wanted a new ECM anyway just in case I brick one....

    7.) Have tried to add a 4ga ground strap from the radiator support to the front cover of the engine, no change. I do have a 0/1 gauge cable on order from Lethal. With that said, I did notice my starter turns slightly faster, so I guess that's good thing.

    Its not the worst problem I've ever had to deal with on a car but its definitely a challenging one.

    If you have had this problem, please say something about it, especially if you've solved it. I'd really could use the input. Thank you, and have a great rest of your weekend.
    Last edited by BOSE ZO; 08-15-2021, 12:37 PM.
    LorenZo
    2018 CHEVROLET Camaro LS -The Giant Black SEALION-
    LGX/TR3160 w/BOZE!!!!!
    ig: rapidtransit

  • #2
    Im assuming it is not under warranty? Sounds to me like a possible connection issue. I would try to make sure all the wiring behind the speedometer is good and tight for starters. It could also be the hall effect sensor that is used to read speed off the tranny. I have heard if they excessively vibrate it can cause this issue

    2002 SOM Z28 Camaro - 12.9 @ 104 mph
    1996 3800 Camaro - 13.43 @ 100.77 mph


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