Strange slipping or possibly downshifting issue on M1009

[RickTheEngineer]

Hey all, here's a juicy one. My M1009's trans likely isn't slipping since it still pulls, however when I am on the highway, or at least in 3rd gear, if you add any noticeable amount of throttle or start climbing a small hill, the engine revs way up, as though it kicked down to second. When you add throttle it does pull though. Afterwards it will go back up to third when you ease on the throttle to just enough to keep whatever speed you were going at. Could this be something up with the vacuum modulator? Any help would be appreciated.

 

[royalflush55]

Check the electric kick down switch located down by the gas pedal. The mechanical slide part will get to where it won't slide properly and try to hang up out of position. Spray some silicone spray lube or wd-40 on it to free it back up. Easy fix if that is the problem.

 

[RickTheEngineer]

Is there a picture out there of what it looks like? I am not entirely sure exactly where that mechanism is! Never knew about it!

 

[porkysplace]

Is there a picture out there of what it looks like? I am not entirely sure exactly where that mechanism is! Never knew about it!

Most likely in the parts TM. They have pictures and diagrams.

 

[royalflush55]

Is there a picture out there of what it looks like? I am not entirely sure exactly where that mechanism is! Never knew about it!

It is mounted on the bracket that the gas pedal fastens to the cab with. It has a plastic slide with a nub that sticks out and the pedal actually pushes it when pushed toward the floor. It will slide down and stick and then not slide back with the pedal.

 

[RickTheEngineer]

Here is all the other details that I can provide. On the highway, when in third gear, it feels as though it just keeps downshifting to second with almost any real throttle input or when going uphill, which obviously causes the engine to just rev up like crazy. But when I let off the throttle, the trans then shifts into third like before. The best I can do is maintain my speed without it dropping to second.
The vacuum modulator doesn't have fluid oozing out of it, the vacuum line has no leaks (on a 6.2 diesel), it has a new trans filter, fluid didn't seem burnt, no metal chunks at bottom of pan, reverse seems okay? Never noticed any slips in reverse.

 

[RickTheEngineer]

It is mounted on the bracket that the gas pedal fastens to the cab with. It has a plastic slide with a nub that sticks out and the pedal actually pushes it when pushed toward the floor. It will slide down and stick and then not slide back with the pedal.

What makes it slide back? Is this how the mechanism should properly function?

 

[RickTheEngineer]

I just went out there to check it out, the switch slides with open throttle and returns when let off the throttle

 

[rustystud]

Have you tried to shift manually ? If you can shift manually then the most likely culprit is the "one-way Sprag" . They are a common repair item. That is why there is a 32 Sprag replacement out there.

 

[cucvrus]

"one-way Sprague" .

 

[RickTheEngineer]

Here's what I can say... When I manually shift to second or first the trans does it without hesitation at any speed, however, with third, it will shift to third but then I can't tell if it's shipping or just dropping to second over and over... My reverse is solid, so I can't immediately so problems there, and there is simply nothing in the pan

 

[cucvrus]

Take it to a reputable transmission shop and have the vacuum valve properly adjusted. Last time I done it I spent $20. It was worth the money. More then likely you will need additional transmission work if you continue to run it in this condition. Sometimes $$$$ is the best tool. Second guessing and getting unskilled opinions from mystery people can lead to greater expense and further frustration. Good Luck. Have a great day.

 

[RickTheEngineer]

That's true... Hmm, I'll just bite the bullet and get it checked out, although considering the state of the trans, I might be better off just spending the money and getting another one to swap in myself. Just something to consider at least.

 

[m38inmaine]

I just had a similar problem with my M1009, headed home from work and when I let off the fuel she down shifted and would not shift out of first. Checked all the usual suspects and they checked out, turned out to be the nylon gear on the end of the governor was worn off. It's just 4 bolts and pop off the cover and the governor pulls right out. May be something to check.

 

[RickTheEngineer]

I'll check it out, although if I recall the governor wouldn't cause random kickdowns? It's hard to tell if it's slipping or kicking down to be honest

 

[royalflush55]

Unplug the wire going to the kick down solenoid on the tranny and see what happens. It is located just above the oil pan on the drivers side of the tranny. Easy to check.

 

[frank8003]

Hey all, here's a juicy one. My M1009's trans likely isn't slipping since it still pulls, however when I am on the highway, or at least in 3rd gear, if you add any noticeable amount of throttle or start climbing a small hill, the engine revs way up, as though it kicked down to second. When you add throttle it does pull though. Afterwards it will go back up to third when you ease on the throttle to just enough to keep whatever speed you were going at. Could this be something up with the vacuum modulator? Any help would be appreciated.

Did this begin to happen after many joyful miles?
Did anyone at all mess with the linkage between the fuel and the transmission, the little switch. Part 11
View attachment M1009 part 11 .pdf

https://www.steelsoldiers.com/showthread.php?40210-M1009-Tranny-auto-downshift-help

 

[porkysplace]

Since you never updated your other thread on transmission problems, maybe this issue , was caused by that issue.
It seems like you have had a lot of transmission problems with this truck.

Transmission leak repair costs...
Mysterious Transmission Leak?

[h=1]M1009 Oil Cooler Lines And Leaks[/h]

 

[RickTheEngineer]

The leaks were actually discovered to be a clogged breather that shot fluid through the tube but ran down to where I thought was coming out of the bellhousing. Since then it has been repaired at leaks stopped. However, as for this problem, it only developed after it drove for another 15,000 miles putting it at a total of 85,000 original miles. Fluid was always at the right level. the linkages posted we're all normal and unmolested. The little switch physically operates normally, but I have to check the contacts. I have yet to unplug the kickdown switch wire and run it like that. She ran like a champ the whole time I owned it, never towed or saw any abuse.

 

[rustystud]

Here's what I can say... When I manually shift to second or first the trans does it without hesitation at any speed, however, with third, it will shift to third but then I can't tell if it's shipping or just dropping to second over and over... My reverse is solid, so I can't immediately so problems there, and there is simply nothing in the pan

I'm pretty sure you lost your sprag. Or like I like to say "sprag-ue" . But do check out your modulator like "cucvrus" mentioned. Also let us know what happened.