m670 three speed

powertech84 · Feb 6, 2016

While i have the engine out, i decided to take a look at the three speed. It slipped real bad in high. Low and direct seemed fine. I pulled the disks out and they look fine, the countershaft gears spin both ways and i found some small pieces in the bottom of the housing, I'm guessing the sprag is out? Would this make high slip? Seems to me i should have also lost at least one of the other gears too. I know this is a rare transmission so i'm hoping someone here has some experience with this to help me out. Thanks

ChrisQ · Feb 6, 2016

I'm no expert on 3 speeds. I've just worked on one in a 950 a little that the sprag was wrecked and the spool valve was stuck in low. I never had the main shaft apart. All of the clutches shifted with air so I left them alone. The countershaft with the sprag should lock up and only spin one way, but to my understanding, it has to work like the 2 speeds, as in when the sprag slips, you loose low range. Ideally I think you should have checked your shift pressures, but that can only be done when its together. If the pressure for high range is too low it would slip. I believe there are O rings in all of that. If you think everything on the main shaft looks okay, I would put in all the o rings and put it together and air test it to verify it shifts. Then pull apart the sprag and look at it since its out. Cross your fingers its good, they are expensive. Then I would say run it and check all the shift pressures and see where you are at. By putting in new O rings and air testing you should have ruled out internal leakage. Best of luck to you.

m670 three speed

powertech84

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ChrisQ

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