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Thread: tachometer conversion?

  1. #1
    Member
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    Oct 2013
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    Northwest Lower Michigan
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    1989 Celebrity CL 4 door 3.1, 1989 Cutlass Cruiser 2.8
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    Default tachometer conversion?

    The tach I put in my Cruiser cluster was listed as from a 2.8 car. But I wondered why it read so high. After confirming I've got a 3.33 final drive, working backwards from the stock tire size appears that it likely came from a 4 cylinder engine. I'm running about 2450 RPM at 55 in OD. TCC firmly locked. My others with 3.33 final drive would read more like around 1800 RPM.

    Is there a cheap and easy way to make it read correctly? Or just have to find one from a 6 cylinder car and hope it's correct this time?
    1989 Celebrity CL 4 door, 3.1 MPFI, 4 speed auto, summer daily driver
    1989 Cutlass Cruiser wagon, 2.8 MPFI (future 3.1), 4 speed auto, future summer ride
    1996 Cherokee XJ 4 door, 4.0, 5 speed, winter daily driver & towing vehicle
    1991 Tracker 2 door, 1.6, 5 speed, needs work
    Previously several Celebritys, 6000s, & 2 U-vans



  2. #2
    Senior Member SexySilhouette's Avatar
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    Austin, Texas
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    1995 Oldsmobile Silhouette, 1989 GMC Sierra C1500, 2005 Chevrolet Corvette, 2001 Pontiac Aztek GT
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    Default

    Perhaps someone would be interested in trading. A 4 cylinder tach is really, really rare.
    Jay

  3. #3
    Member
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    Oct 2013
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    Northwest Lower Michigan
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    1989 Celebrity CL 4 door 3.1, 1989 Cutlass Cruiser 2.8
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    Default

    Hmmm. I pulled the cluster tonight and well the outside of the cluster has a GM sticker that says 6 CYL. I pulled the tach itself and the number on the back of the circuit board is 25054151, if that means anything. I'm not sure it the tach itself, or the cluster, controls whether it will work with a 4 or 6 cylinder car. I guess it's possible someone stuck a tach from a 4 cylinder car in the cluster. The cluster did come from a car with a 3 speed trans, but the 3.3 had that too.

    It's nice that the Ciera tach has the terminals labeled. I've got 3 boxes of old gauge cluster parts for Chevy and Pontiac. If I can get a tach from a 6000 (all were V6 cars) I can try piggybacking it to the Ciera tach terminals and see if it reads the same, or what's going on.
    1989 Celebrity CL 4 door, 3.1 MPFI, 4 speed auto, summer daily driver
    1989 Cutlass Cruiser wagon, 2.8 MPFI (future 3.1), 4 speed auto, future summer ride
    1996 Cherokee XJ 4 door, 4.0, 5 speed, winter daily driver & towing vehicle
    1991 Tracker 2 door, 1.6, 5 speed, needs work
    Previously several Celebritys, 6000s, & 2 U-vans

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