Pete 379 air leak, 3 hrs and can airbags are empty.

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 .

 

If you have enough air to release the parking brake the transmission should shift. Try search block at top right.

 

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.

 

Your tranny is also warming up , the valves are warming up with it . Most likely sticky valves work better when warm

 

Yes pretty simple . Locate the valves on the tranny ( air lines running to them ) disconnect air lines and take them apart and clean . Brake cleaner works well . blow them all out with an air hose and lubricate all moving parts with silicone lubricant spray . or any LIGHTWEIGHT oil . Nothing heavy or they will stick again or maybe even worse