939 series will not shift manual

[corvette9]

My 936a2 shifts fine. I would like it to hold a lower gear when going up steep hills. I tried adjusting the line pressure at the throttle linkage and that seamed to firm up the shifting but it still shifts to the next gear to quick and you loose the power band. It will drop down below 1500 rpm before it will down shift again.

So I tried shifting the truck myself. Here's where it gets weird. I can put the shifter in any foward gear and it will still shift as if it was in 1-5. Even if I put the selector in 1 it will still shift all gears. Now the shifter seems to work fine. I checked the shift lever on the trans and it moves as it should with the shifter. It go's into N or R no problem.

I never drove a 900 series before this one so I have nothing to compare to.

Any ideas as to why it won't let me shift manual? Is this just normal? I don't see how but these trucks are nothing like the old 5 tons I had year ago.

 

[M35A2-AZ]

You should be able to manual shift the truck. Sound like the linkage in not working right.

The M936 does die on the hills for sure!!!!

 

[Floridianson]

You say it shifts was just wondering if it shifts at higher RPM. I just got my 931 and yes mine if I place it in one one it will carrie that gear till 2100rpm then I shift to second and 2000rpm again Ect Ect.

 

[corvette9]

That sounds like the way it should work. Whatever gear you put the shifter in it should stay there till you move the shifter to the next gear

My car carrier has a Cat 7.2 and Allison trans. If I put the shifter in 1st gear it will not shift out of first even if the engine is redlined.

 

[Suprman]

All of mine stay in whatever gear I put the shifter in. I have never driven a wrecker though I know it is significantly heavier than my tractor and cargo trucks but it shouldnt make a difference

 

[KenaAuto]

My 925 doesn't stay in manual gears either. I thought that was strange, but for what I use it for, it's not worth the time to track the problem down.

 

[quickfarms]

In auto what rpm does it shift at?

What is the governed rpm of the engine?

What is the model of the trans, check the tag on the side of the trans.

The shift points are adjustable, but you have to drop the pan to do it.

If the transmission has a low low first it can be set to stay in that gear.

Typically they are set to shift at the governed rpm to protect the engine in a downhill situation.

I have seen a lot of these truck in which the shift points are not correctly set.