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Discussion Starter #1
I'm looking to put a tach on this engine using the pickup that reads ring gear teeth, but am getting mixed info on the tooth count. (the parts book, and service manual have 2 different numbers).
Engine is in a case and the tag reads:
4t-390 Part no:A174324
Serial: 44494903

quickserve doesn't like that serial #, and I really don't want to pull the trans just to count teeth.
 

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Discussion Starter #2
FWIW engine is in a dozer, and I need the tach to try and troublshoot a torque converter/hydraulic problem
 

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I recommend the Tiny-Tach. It is digital and the transducer attaches to an injection line. It is very accurate because it "reads" the injection pulses.


I've had mine for several years, first in the bread truck and now in the F150.

Using it in a dozer, you might want to find out about water resistance.
 

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p.s. No worries about tooth count
 

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What's the model of your Case dozer? For example, the model 650 has ring gear J901774 or Cummins 3901774 which is 159 tooth. That was probably pretty common on Case engines.
 

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Discussion Starter #6
What's the model of your Case dozer? For example, the model 650 has ring gear J901774 or Cummins 3901774 which is 159 tooth. That was probably pretty common on Case engines.
The dozer is a 1991 650. The parts book says 159 tooth, but for some reason the service manual says 127 tooth (in the section for stall testing the converter and hydraulics)
 

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First off, is yours a straight 650? There is a 650, 650G, 650H, and 3 versions of the 650K. The plain 650 only shows one flywheel with the 159 teeth. The 650G and 650H has a flex plate instead of a flywheel and there are 2 different ones depending on the serial # of the dozer. The 2 flex plates are J934936 (Cummins 3934936) and J934937 (Cummins 3934937). The J934937 is 159 tooth and I suspect J934936 is too. 127 tooth doesn't sound right for an SAE3 flywheel which is what those dozers have.
 

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Discussion Starter #8
The dozer is a straight 650, no letter after it.
Thanks for the help.
here is the service manual page that is causing the confusion
126684
 

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Here's link to Coleman Equipment site you might find useful. They are a Case industrial dealer and have a great parts catalog on line with lots of detail If you see a Case part number beginning with the letter J, change that to a 3 and you have a Cummins part number. This site will show you virtually every nut, bolt, and screw in you 650. https://www.colemanequip.com/parts/model/Case-650-Crawler-Dozer-Parts/
 

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