Screamin" Engine

[tom lovinggood]

Hello--took my M1009 out for a spin a few weeks ago. Started right up with no problems. Took it out on the highway close to my home and was going up a fairly steep hill, when, all of a sudden. the engine revs up and begins screaming as it went up the hill. I don't ever recall my engine doing this? It ran fine, and when I leveled off, the transmission changed gears and the reving slowed down to a nromal RPM. Does anyone have any thoughts about this high reving with their M1009? Everything else functions fine and had no other issues.
thanks in advance
Tom Lovinggood

 

[WWRD99]

You described the engine revving high after it downshifted to 2nd gear on a hill? Has it done this before on that hill? You loaded up in the bed or pulling anything? If it's something new, downshifting without a load on the engine going up a hill, then I'd look into the vacuum modulator on the side of the trans...pull the vacuum line and make sure no transmission fluid is in it...the other is the governor in the trans...it's under the circular cover on the side of the trans...it might have a broken spring...both of these can be done with minimal transmission experience...the vacuum solenoid might be off some as well...if it doesn't do the low shift thing a bunch it might be tough to find yet though.

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[tom lovinggood]

WW--thanks for your reply. I will look into this.

 

[MarcusOReallyus]

Check the vacuum lines, too. If they leak, shifting gets wonky really fast.

 

[ezgn]

Check the vacuum lines, too. If they leak, shifting gets wonky really fast.

I don't push my motor ever to make it shift. Just let it slow down and take your time and if it needs to shift on it's own without forcing it it will down shift. To each their own, I drive my truck conservatively knowing that it is engineered within limits of torque speed and rpms. I don't remember my truck ever downshifting just climbing a hill without a load, maybe your just wanting to go to fast up a hill. Peace.

 

[MarcusOReallyus]

I don't push my motor ever to make it shift. Just let it slow down and take your time and if it needs to shift on it's own without forcing it it will down shift. To each their own, I drive my truck conservatively knowing that it is engineered within limits of torque speed and rpms.

Well, that's probably good advice, but I don't know what it has to do with the OP's new shifting problem.

 

[ezgn]

Well, that's probably good advice, but I don't know what it has to do with the OP's new shifting problem.

I'm just saying that down shifting to a lower gear going from a higher speed than what that gear is geared for would cause excessive rpm's

 

[MarcusOReallyus]

Of course it would. That's clearly the problem, and it's something new. He's driving the same way he always has, and, unlike before, it's downshifting when it should not.


That spells out a mechanical problem, not a driving problem.

 

[WWRD99]

I'm just saying that down shifting to a lower gear going from a higher speed than what that gear is geared for would cause excessive rpm's

The trans has built in a governor by line pressure to force the upshift if the rpms (speed technically) are to high...the downshift is weird with these since they have a vacuum pump that over rides the governor to allow a downshift...I always describe the governor and modulator in a constant fight to win line pressure...if it got to much vacuum it could downshift when it shouldn't...it would have to be a lot though or if the modulator diaphragm is ruptured it causes really bad shifts...going furthur in the trans, the modulator valve spring in the valve body might be weak or the valve itself sticking.

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[nyoffroad]

This sounds overly simple maybe to the point of being stupid, but while your checking lines and weights and such make sure you check the fluid level. Yours wouldn't be the first trans to slip going up a hill when low on ATF.