GOOG Posted June 30, 2015 Share Posted June 30, 2015 I have a 1997 CL 713 tri axle dump, with a 12 speed Mack trans. I did a search on 12 speeds and saw where you will have trouble on pre select shifts if air pressure is too high. I have exactly that problem. Where is the regulator in question. Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted June 30, 2015 Share Posted June 30, 2015 On top of the box but what's the problem before you get into ripping it all apart?Paul Quote Link to comment Share on other sites More sharing options...
MACKTRUCKS4 Posted June 30, 2015 Share Posted June 30, 2015 It's on a plate mounted on the left rear side section of the trans. Follow the air line from the trans air filter to the regulator. You should not pre-select a 12 speed trans because it will shift the first chance the gears free up even if your not ready. 1 Quote Live every day like it's your last, because one of these days, it will be. Link to comment Share on other sites More sharing options...
GOOG Posted June 30, 2015 Author Share Posted June 30, 2015 My complaint (and I read where I'm not the only one who has experienced it), is when I am upshifting through the gears I can't pre select in 1st, or 2nd gear. The air shift will take place before I can move the stick, causing a violent down shift situation. I can go from 3H to 4L and up without difficulty. I saw on another thread on this forum where this is probably caused by the air supply to the shifter being too high. The other poster made reference to youtube videos, which I checked out, and found my situation is not the norm. Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted June 30, 2015 Share Posted June 30, 2015 yep sounds about right as soon as you flick the switch on the knob the they try and shift and as described above in post 3 you shouldnt really pre select as it puts load on the selector fork and its only the engine load on the transmission that stops it shifting as soon as you flick the switch the selector fork is wearing (dunno if that makes any sense)as you say it sounds like your air pressure is to high and because the air rams are inside each other one way has a bigger ram than the other which is also as you describe ie it will do it shifting up but not down also some are plumbed up with only one regulator some with two so maybe only one of the regulators is crook if it has two if that makes any sense you can hook a air pressure gauge up to each side of the ram and see which regulator is crook dunno if any of this makes any sense at all Im sure someone else will jump in and explain it a lot better if I have ballsed it up Paul Quote Link to comment Share on other sites More sharing options...
gearhead204 Posted July 2, 2015 Share Posted July 2, 2015 the maxi torque decal on the visor says to preselect! i have had problems with them by not preselecting maybe i just do it diffrently than others, i preselect just before i move the shift lever from one hole to another. when shifting between direct and over i treat it like a 2sp. rear end, i also clutch or doubble clutch most shifts. Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted July 2, 2015 Share Posted July 2, 2015 yeah you have to pre select it just before you shift poor explanation from me I dont think it would change any good if you tried to shift it at same time as shifting the stick I always clutch any stick shift but thats just me and am no expertPaul Quote Link to comment Share on other sites More sharing options...
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