Pete air trac problem

I have a 94 peterbilt 379 with air trac. It started having an issue about 1 year ago that has progressively gotten worse. The leveling valve will try to dump air to get suspension back to level, all the while trying to inflate at the same time. It’s e changed the leveling valve twice ( by recommendation of peterbilt dealer mechanic) have tried setting ride height to factory specs. Replace all airbags, air bag saddles, almost every airline ( being they were due). Leveling rod has been replaced and cut to spec for the 11 inch ride height requirements. Replacing the leveling valve would make the problem stop for a short period of time but then comes back. When this happens while driving down the road, if I dump my bags quickly it will go back to proper operation. If I go around a corner, go up hill or down or am on an uneven surface it will start all over. It makes the compressor run non stop. Makes the air dryer kick off every 40 seconds. I spend half my time off road empty being I own a log truck so I am on a lot of bad roads. Lots of steep climbs and uneven terrain. The only thing I haven’t replaced is the dump valve that is tied to all four air bags. Anyone have any ideas where to look next? It’s making me insane and I can’t seem to get this problem nipped! Thank you in advance for any suggestions. I’m willing to try anything at this point!

 

Come to find out there are 2 different length leveling rods for the air track from the factory. Depending on what model differential you have, require different length leveling rods. One is 15 inch and the other is 18. Peterbilt put the 18 inch on while at the dealership and it was supposed to be a 15. The mechanic wasn’t paying attention when he replaced it. Been fighting it all this time and it was right in front of my eyes.