14 vnl with cummins pto mode issues

So i have a cummins powered vnl and i drag around a Pnuematic tanker so i recently had a pto installed with a blower setup. My issue is intermittent but what happens is when the truck is running under load in pto idle up it will start pulsating and if the load is not removed or lessened the truck will start violently shaking. Once this happens it’s like it gets stuck in this mode and whenever i try to continue to apply the load via the blower it will do this. Also when this happens the eld will be switched into drive mode screwing up my clocks. I have gotten to the point where i use a clamp and manually set the idle up using the pedal, so i can finish unloading and move on. Volvo says theres nothing that needs to be set up in the computer because it is a manual trans and not an auto. The blower has been checked 3 times and we even swapped out the pto to a unit with a higher rpm, that seemed to help some but not completely. What sensor(s) are used to control engine rpm under pto load? I know the cruise control system uses the tailshaft speed sensor while driving, but that is an external sensor with the tone ring on the output yolk. Would really like to get this fixed so i can get these loads of mine done in a timely fashion.

 

We have checked all the settings with insight that would pertain to a truck with a manual trans, all seem to be ok

 

Not really fixed but in my case there was some play where the output of the pto shaft attaches to the driveshaft for my blower. There are two square head bolts that tighten it to the output shaft and one was just ever so slightly loose causing my issues. I also had a busted u joint as well. I say not really fixed because i noticed that when i dont grease all the zircs for the u joints and slip joint every week it will start acting up again. But if you have an auto trans you’ll need to have the dwell adjusted for the pto mode

 

Unfortunately there are no settings that pertain to the manual trans trucks except for the max rpm. You can adjust the dwell if you wish to allow a more fine tune of the amount of rpm it goes up or down when pressing the acc button. Is this a new install or did this start after a while of running?

 

Also my truck doesn’t like anything higher than about 950rpm but just like yours runs smooth with a clamp.

 

I had the most issues after i had my blower installed it turned out the blower was bad not sure exactly what it was but after i got a new blower installed I didn’t have any issues for a long time then one of my u joints went out as mentioned above and thats when i started having issues again even after installing a new joint. Ultimately i found the loose square head bolt. Now when i say loose i don’t mean physical loose as when i put a wrench on it there was some force needed to turn however that removed the play and so far so good. The truck still shakes but doesn’t go into crazy mode