pete 379 high/low leaking

I got an air leak under the cab of the truck, a 1999 peterbilt 379 tractor only in high gear. The leak is on the side of the high/low selector behind the air line. there's a hole on of the castings and the other case half has a tang that covers it. The hole does not go anywhere, but the air leak is around that area. We had the selector apart and could not find any obvious signs of air leaking. The o-rings and gaskets all looked good. Which lead me to beleive that a sealed internal component is leaking into the chamber causing it to leak out of the assembly. Anyone ever run into this? Peterbilt want 427$... so looking for advice, thanks!

When you say "selector", are you talking about the air cylinder, or the safety valve? What transmission are we talking about?

If you could post a few pics it would be helpful.

The model number on the side is FRO16210C. Eaton trans. The leak on occurs in with the button put in high. The unit that's leaking is bolted to the top of the transmission. I've seen it referred to as different things, so not sure what it's actually called. Hi-Low valve, Range selector, Range actuator valve... Not sure. But it leaks, and leaks bad when high is selected.

Illustrated parts list for FRO16210C > http://www.roadranger.com/ecm/group...oadranger/documents/content/rr_fro-16210c.pdf

willie59 said:

Illustrated parts list for FRO16210C > http://www.roadranger.com/ecm/group...oadranger/documents/content/rr_fro-16210c.pdf

Click to expand...

Willie if I remamber right the range shifter o ring will let it bleed air like that.I removed one a cleaned cylinder and lubed the o ring and it worked fine.Done one this way that wouldn't shift with out grinding.

2 stick, are you talking about the orings ontop of the trans under the air module assembly. On the parts blow up through the link willie put, item 3 on page 4? Or something internal? From what peterbilt said, the air module is a non serviceable item. Yet I've heard of people opening them up, lubing them, and replacing o-rings.