Hey guys me again. I know this is a needle in the haystack post. I have an appointment at shop wed. But i figured i would ask you guys as well. 06 379 with 18speed tranny. I can leave my truck and after 3 hours the can air bags are completely empty. Suspension bags still full. And then once i start truck and let it warm and build air pressure to 150. My transmission doesn’t work on the high side (switching the grey switch) takes a good 20 mins riding down the road. (I’m guessing the air gets back built up) then the high low switch will work. Is this maybe a major transmission air leak or line going to it or something else. I know it’s hard to say but maybe someone else has dealt with this
Pete 379 air leak, 3 hrs and can airbags are empty.
Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by believe456, Jan 5, 2022.
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18 speeds from 06 were notorious for the selector switch on the tranny itself getting sticky from contamination in the air system , i used to take them apart and clean them up real good and lubricate them with silicone based spray . Good for quite a while again. As for the air leak could be a hundred different places , the air stays in the ride bags because its not going to flow back through the leveling valve . Pick a rainy day and a quiet spot and look listen and gently move air lines around . A spay bottle with soapy water works wonders too. I would bet the tranny problems shifting are the valves not the air leaks though .
BoxCarKidd Thanks this. -
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As was mentioned you have a contamination issue. It works after driving because you have built enough heat to free up the binding parts.
Think of the difference in fifth wheel grease on a summer day vs a winter day. -
150? Thats pretty high. I’ve experienced in the past that some valves and things do not work very well if psi is above normal working range. Most trans only need 90 and are regulated at such. 130 can sometimes put to much stress on things in the system and thats what i try to set purge at if governor will let me.
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