4bt Tach / Rpm reference or crank sensor - Page 2
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Thread: 4bt Tach / Rpm reference or crank sensor

  1. #31
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    The easiest and cheapest way i found to get a tachometer to work with a
    4bt was to purchase one that can be used with a magnetic pick-up that counts the teeth on the flywheel.
    Just drill & tap adapter plate directly over flywheel teeth and install pick-up.
    Tach $16.00 New surplus. 3"dia. 0-5000rpm.
    Mag p/u $28.00 Truck parts house.
    Sergio.

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  3. #32
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    Quote Originally Posted by Diesel Durango View Post
    cutting the same number of teeth as a flywheel into a harmonic balancer sounds like a nightmare.
    Not all of the teeth, just the crankshaft sensor blips.... like these. These are the Jeep 4.0L marks. Would have to use a 6BT balancer due to the lack of meat on the 4BT pulley.



    --Scotty
    2000 Jeep TJ. 4BT, NV4500, NP231, D30/D35, 5.5" Longarm, 35" MTR's, 3.73 gears.

  4. #33
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    Quote Originally Posted by 4bt Terra View Post
    a magnetic pick-up that counts the teeth on the flywheel.
    Just drill & tap adapter plate directly over flywheel teeth and install pick-up.
    Tach $16.00 New surplus. 3"dia. 0-5000rpm.
    Mag p/u $28.00 Truck parts house.
    How would you calibrate that?

    My Dakota Digital unit threaded right into the block adapter and was fairly easy to program. My "Ford" flywheel has 146 teeth.
    1979 F-250 4WD, NP435 trans, NP205 TX case, 3.54 gears. IP turned up, H1C from 1993 12V with 12cm housing, 3" in and out FMIC.

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    Quote Originally Posted by fitty View Post
    Not all of the teeth, just the crankshaft sensor blips.... like these. These are the Jeep 4.0L marks. Would have to use a 6BT balancer due to the lack of meat on the 4BT pulley.



    --Scotty
    I've never seen that pattern, my durango AFIK doesn't have those wide tics. It was an auto, so no flywheel, just a flex plate. Maybe i am missing something here. I have seen the hesco unit before.

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    I'm only throwing this out for head scratching & further research: When I installed my Dodge NV4500 I found that there was a speedometer drive on the rear. It was from an '02 Dodge, electronic everything, and I was shoving it in a '67 Dodge electronic nothing. Turned out I could remove the electronic hall effect sensor that was attached to the speedometer pickup gearbox in the tailshaft and simply screw in my analog speedo cable.

    Possibly that same Dodge electronic [Hall effect clock-pulse?] sensor could be incorporated as a tach drive pickup with a signal converter for clock pulse count. May look into that myself on my own truck.
    Last edited by JimmieD; 12-19-2007 at 10:26 AM.

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    Quote Originally Posted by JimmieD View Post
    I'm only throwing this out for head scratching & further research: When I installed my Dodge NV4500 I found that there was a speedometer drive on the rear. It was from an '02 Dodge, electronic everything, and I was shoving it in a '67 Dodge electronic nothing. Turned out I could remove the electronic hall effect sensor that was attached to the speedometer pickup gearbox in the tailshaft and simply screw in my analog speedo cable.

    Possibly that same Dodge electronic [Hall effect clock-pulse?] sensor could be incorporated as a tach drive pickup with a signal converter for clock pulse count. May look into that myself on my own truck.
    Using the speedo output would give you a rpm source only when in high gear, unless you did all the calculations for your different gearing. That would be to complex for my little brain to keep up with while driving. You would have no output while in neutral. With an automatic transmission everything would be inacurate due to torque converter slipage.

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    Yes... I am using steel screws, 10-32's to be exact. I actually finally drilled them tonight and am pulling out my hair looking for my taps! Somebody asked about the size for ideas.. the reasoning I had behind it was the head of the screw should be big in diameter as the end of the sensor so it gets a good magnetic reaction. I KNOW it won't work on aluminum alone.. come on guys..give me some credit. I also finally got the remote tps sensor and have to fab a bracket for it.. THEN do the IFS lift and I'll be on the road.
    93 FS Blazer 4bt/4l60e/np241

  9. #38
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    Quote Originally Posted by 4bt Terra View Post
    The easiest and cheapest way i found to get a tachometer to work with a
    4bt was to purchase one that can be used with a magnetic pick-up that counts the teeth on the flywheel.
    Just drill & tap adapter plate directly over flywheel teeth and install pick-up.
    Tach $16.00 New surplus. 3"dia. 0-5000rpm.
    Mag p/u $28.00 Truck parts house.
    Sergio.
    What's the part number of this elusive $28 pick up?
    Last edited by torquenturbo; 12-20-2007 at 05:04 PM.
    93 FS Blazer 4bt/4l60e/np241

  10. #39
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    O.k. guys here's what i'm using.
    Tach is a Auto Meter Industrial (AMI) p/n 1785
    3 3/4" electrical 5000 rpm probe tachometer.
    You can calibrate by turning an adjustment screw on the backside.
    As for the mag pick-up it is a VR Speed Sensor p/n SAA85920008.
    Sergio.

  11. #40
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    if you try SAA 85920008 (saa-separated) it looks like a Freightliner number. On the web I can only find Russian sites selling it? I'll have to check it out. Any pics? Does it have a steel body or plastic? What does your setup look like?

    LincTex: You have any pics of yours? No such luck of a whole on the Chevy Bell. Is your sensor perpendicular to the flywheel teeth? Also, my worry was that the Dakota Digital translator box wouldn't put the correct square wave DC signals the TCI trans controller is looking for.
    Last edited by torquenturbo; 12-20-2007 at 05:12 PM.
    93 FS Blazer 4bt/4l60e/np241

  12. #41
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    Quote Originally Posted by torquenturbo View Post
    1) LincTex: You have any pics of yours?
    2) No such luck of a whole on the Chevy Bell.
    3) Is your sensor perpendicular to the flywheel teeth?
    4) Also, my worry was that the Dakota Digital translator box wouldn't put the correct square wave DC signals the TCI trans controller is looking for.
    1) Don't have a camera handy right now but it looks just like this:

    2) The Ford small block adapter has the correct 3/4" - 16 hole about 6 inches above the starter on the pass side
    3) Yes
    4) Maybe Dakota Digital could answer that
    Last edited by LincTex; 12-20-2007 at 05:56 PM. Reason: typos
    1979 F-250 4WD, NP435 trans, NP205 TX case, 3.54 gears. IP turned up, H1C from 1993 12V with 12cm housing, 3" in and out FMIC.

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    You can see the sender hole in the block adapter in this picture, about 6" above the starter (red plastic plug)
    1979 F-250 4WD, NP435 trans, NP205 TX case, 3.54 gears. IP turned up, H1C from 1993 12V with 12cm housing, 3" in and out FMIC.

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    Torquenturbo; I have a few extra mag pick-ups if you're looking for one.
    They are in a plastic housing.
    Sergio.

  15. #44
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    anyone able to tell me how "thick" a 6bt balancer is?

    I think it might interfere with my front engine mount.
    2000 Jeep TJ. 4BT, NV4500, NP231, D30/D35, 5.5" Longarm, 35" MTR's, 3.73 gears.

  16. #45
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    more in the same vein as the mopar igniton idea, i needed an extra sensor a while ago for an add on odometer. the pos car's speed sensor wasn't compatible. ( most are. ) i ended up using an aftermarket cruise control pickup. these put out a sine wave. they come with 2 magnets. if you mounted the magnet 180 deg. from each other and hooked them up to a mopar ignition module using the ceramic resistor instead of the coil. it would have to work. either that or hook it up to a gm efi module that was made to convert from sine to square for efi. ( not sure what got this setup in the states. i have seen some accel ones, so they must be reasonably common. ) something to think about anyway.
    It pulls like a 14 year old with a playboy !

  17. #46
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    nobody able to help me? need to know how thick a 6bt balancer is.
    -Scotty
    2000 Jeep TJ. 4BT, NV4500, NP231, D30/D35, 5.5" Longarm, 35" MTR's, 3.73 gears.

  18. #47
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    couldn't find a good tape measure,but i get 7/8" on my 95 balancer.

  19. #48
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    only 7/8? I get about that on my stock 4bt pulley.
    2000 Jeep TJ. 4BT, NV4500, NP231, D30/D35, 5.5" Longarm, 35" MTR's, 3.73 gears.

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