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When I put the 12 spd. in my superliner, I did the same set up. Mack pto, called my local mack dealer and he faxed me all the papers he had on the mack pto with air shift. That was a few years ago and I got everthing from mack. Air cylinder, brackets, hardware, etc. I may still have all the papers somewhere, will look when I get time.

Live every day like it's your last, because one of these days, it will be.

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  • 8 years later...

ok....  Can you give more info on your issue, and Im guessing this is an MR or LE?  are there multiple issues?   many guys here to help you..  jojo

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follow the air lines back to the tank.  if they go to the same fitting, or pressure protection valve, it is probably stuck..  if that is what is there, you can remove the valve and hook the lines direct, just to get it to a shop, or off the job site.  what model is the truck..  I think 1M2P2 is an RD..  is this a U.S. truck?  jojo

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  • 1 year later...

I believe you put the aux. Box in neutral, then you can select 1st-3rd depending on the PTO speed you need. It's been over 20nyears since I drove a 2 stick R/DM model dump truck. 

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Yeah, I may have spoken out of ignorance!  I'm thinking back to a particular truck I remember.  It had a 2-stick Maxitorque "Extended Range 6-Speed".  On that one, if the mainshaft wasn't turning, there was nothing happening in the rear box either.  Not sure where the PTO was mounted on it, though.  That one required the front box to be in gear to spin the PTO.  But, you had a selection of PTO speeds to choose from, which was useful sometimes.

But, since the countershafts are powered even when the front box is in neutral, I suppose you could power the PTO off of one of them, albeit at a constant ratio.

TJC, you've got me curious.  What box did you have where there was power coming off the auxiliary when the main was not turning?  That's an interesting setup.  I'd like to see how they routed the power through that one.  Sure would like to know more about that one!

"Eagles may soar, but weasels don't get sucked into jet engines."

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not sure what trans it was other than a twin stick. driver side was main, passenger side stick was reverse to you and back, low away and up, and direct away and back.

the 85 R models was main in gear, aux in neutral. the 79 DM was main in neutral and aux in gear. 

but now that i think of it, they were not air pto, they were mechanical shift. 

  • Like 1

when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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Not sure which trans the OP has, but here is some verbiage from a service manual that talks about air-shifted aux versions...

This particular group works like the one I remember using...neutral on the rear box for PTO.  But, again, this may not be the right group for the OP.

image.png.ddea7afaa43714bf2fa75ecbc7c445bf.png

"Eagles may soar, but weasels don't get sucked into jet engines."

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