Warpman89 Posted November 8, 2011 Share Posted November 8, 2011 Gentlemen, I have a problem. I have the trtxl1070b 12 speed and lately I have had trouble getting it into reverse and sometimes high range, both of which are shifted by air as you well know. Furthermore, when the High-Direct-Neutral-Reverse control valve/knob is in direct, I have a lot of air coming out of the exhaust line that comes off of the knob. When I had trouble shifting into reverse in the past, I would roll forward at a low speed and air shift into reverse, but now I am no longer able to even do this. Do this sound like the knob needs to be rebuilt or what? The transmission is a rebuilt unit which was installed about one and a half years ago. Everything worked fine after installation. I ordered a knob rebuild kit from Mack today. They had two available, the "major" kit and the "minor" kit. I got the minor kit because it was about $100 cheaper, though it probably not as complete. Any help on what the problem might be or advice on how to install this kit would be very helpful and appreciated. Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/ Share on other sites More sharing options...
BAD DOG Posted November 8, 2011 Share Posted November 8, 2011 Probably slipped an o-ring on one of the shift cylinders on top of transmission. not expensive yo fix, last kit I bought cost about $25. Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/#findComment-90235 Share on other sites More sharing options...
Warpman89 Posted November 8, 2011 Author Share Posted November 8, 2011 Do you or does anyone else here have an exploded diagram of the shift cylinders? Now that you mention it has all the symptoms of a missing or slipped o-ring Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/#findComment-90236 Share on other sites More sharing options...
BAD DOG Posted November 8, 2011 Share Posted November 8, 2011 I've got an overhaul manual here, I'll dig it out and see if I can get it posted for you. Not too tough of a job to rebuid shift cylinders there on a plate at rear of trans. hardest part is getting them in and out of truck. If I remember right you have to center the reverse piston by turning the adjustment screw on the cylinder all the way in and backing it out half the amount of turns it took to turn it all the way in. Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/#findComment-90240 Share on other sites More sharing options...
storkmack Posted November 8, 2011 Share Posted November 8, 2011 Call Jared over at our shop 815.378.1241. Pretty sure he has the manual. -Brad Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/#findComment-90269 Share on other sites More sharing options...
Warpman89 Posted November 10, 2011 Author Share Posted November 10, 2011 Thanks stork Quote Link to comment https://www.bigmacktrucks.com/topic/21480-calling-all-12-speed-experts/#findComment-90457 Share on other sites More sharing options...
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