another cat 7155 question

[jwb79]

our one m917 came in today because as soon as you release the air you hear the air blowing right into the breathers. the high in gear you get the more pours out until the valve trips. i was thinking it was the reg going bad. or needed rebuilt. our foreman said pull it and see what it might need. well i did and was careful with the shims i looked at the plunger in side and it is scared up pretty bad and the o-ring on it seemed worn. so i put an o-ring on put it back together and started it i had no blow by in the breather but it sounded like a wood pecker. so i need to pull back off any idea what the problem could be with the blow by and what could be the the sound i now let it make?

 

[NDT]

Does the shifter sound like a woodpecker or the transmission? Either way the shifter needs to be in good working order for the transmission to work correctly. I would pull it apart and VERY CAREFULLY rebuild it with O-rings that are exactly the correct size. As you know the actuation plunger pops out under 60 PSI.

 

[jwb79]

the reg it self is making that sound. the thing is no one at work even knows where to get parts for it. the cat dealers get quite on the phone when you ask them. i have a few tm's but very little on the trans in them. im trying to fig it out because the mind with this trans at work is scrap the truck. i dont want that

 

[Nonotagain]

the reg it self is making that sound. the thing is no one at work even knows where to get parts for it. the cat dealers get quite on the phone when you ask them. i have a few tm's but very little on the trans in them. im trying to fig it out because the mind with this trans at work is scrap the truck. i dont want that

Tell them to scrap it and I'll purchase it at scrap metal prices as long as the Cummins ain't broke.

 

[NDT]

Cat cannot help with parts for this transmission. The military had some civilian rebuild shops lined up for overhauls, (one at Ft Polk, LA) but with the surplusing of the M915/916/919/920's, the party is over there as well. If your company wants to use this truck commercially, tell them that a manual transmission swap is probably a must. If the pressure regulator is "woodpeckering", bypass it and run the air up to 100 PSI and see if proper shifting comes back.

 

[Floridianson]

The manual is still avabile from Cat.

 

[BKubu]

If you continue to have problems, buy a rough M920, M916, or M915 and pull the entire transmission assembly. It would not be a bad idea to have extra parts on hand.

 

[R Racing]

Try some air tool oil in the lines and airtank under the drivers side . It may clean some of the sticky stuff out. Also I don't know if you have this Mod or not. My M920 has ithe air inlet to the compressor moved from the inlet , To the side of the engine block so it pulls oil vapors to lube everything . I haven't seen many done that way . But it seems to work to keep things lubed.

Jim

 

[jwb79]

lol thing is they could do just that no joking aside that engine has a new fuel and jake system on it

 

[wreckerman893]

Sometimes if you are having shifting issues you can put the tranny in neutral and let the air build up as high as it will go (around 120 PSI) and then push the valve in on the tranny...if there is crud in there the extra air pressure will blow it out....used to work for me.

Lots of times an impatient driver will put the tranny in gear before there is plenty of air in the system.

 

[jwb79]

thanks for the tips i tried a few i found the reg needs new o-rings things cant find a kit no where i used some thin coat of grease around the o-rings and it worked. but since we r unable to find a kit it will headed to the sale line. so if any of ya from wv and ohio area they will be at the sale line here soon. be good parts trucks. im keeping an eye on one of our 6x4 for when they send it

 

[R Racing]

did you rebuild the air shifter and replace the O rings ?