Air leak in Allison? - Printable Version
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Air leak in Allison? - HoosierDaddy - 08-13-2020
I was under the Newell chasing air leaks when I noticed a distinct gurgling sound in the transmission pan. It sounds like air leaking into the fluid and bubbling. I can feel it when I touch the pan. So far I have found nothing on the web regarding this. Any ideas from my fellow Gurus?
RE: Air leak in Allison? - Fulltiming - 08-13-2020
My first thought was the air shifter could have a blown seal but I don't think the air shifter has any direct connection into the transmission. It merely pulls and pushes the shift rod on the outside of the transmission. I would check the level of the transmission fluid first. If it hasn't been changed in a while, you might consider changing the transmission fluid. Changing the transmission filter might not be a bad idea either.
RE: Air leak in Allison? - HoosierDaddy - 08-14-2020
Thank you, Michael. Actually I was replacing the air supply line to the shifter that was leaking. The Bennet air shifter bolts to the side of the trans. The only other connection to trans is the linkage to the trans shift arm. Fluid and filters changed 8,000 miles ago. I’m wondering if it has something to do with a trans cooler.
RE: Air leak in Allison? - Richard - 08-14-2020
Couple of primitive diagnostic questions.
Was the tranny hot, or was this in a cold situation? If the coach had been sitting for a while, I doubt the tranny cooler is draining back into the allison and gurgling
If you release all air pressure from the coach systems, does it stop? If so, I would disconnect all the air connections to the shifter mechanisms, cap them, and repressurize. If it doesn't reappear, then at least you have narrowed the search field for the leak.
RE: Air leak in Allison? - ccjohnson - 08-14-2020
Sounds like the Williams shift modulator. I've had to replace a couple of them. I'm in AZ today or I would send you a pic & part number. Can do that when I get home if you want.
RE: Air leak in Allison? - HoosierDaddy - 08-14-2020
That would be great thx
RE: Air leak in Allison? - HoosierDaddy - 08-14-2020
Richard,
I only hear it when the coach is aired up. There is no air connection from the shift actuator to the trans. I noticed it at approximately 80 degreesF. I am almost sure it is inside the trans pan. I'm trying now to determine if it is something I can dig into or take to an Allison dealer. It seems that air modulators are used when an air accelerator pedal is installed. Mine is an electronic accelerator pedal.
RE: Air leak in Allison? - ccjohnson - 08-15-2020
This is what I have on the modulator.
RE: Air leak in Allison? - HoosierDaddy - 08-15-2020
Hmmm It looks like that plumbs into an air accelerator circuit. My accelerator pedal is all electric. My 8v92 is electronically controlled.
RE: Air leak in Allison? - Richard - 08-16-2020
Ok so it only gurgles when aired up. You say there is no connection from shifter to tranny but that is the way only device air activated that is attached to trans. Take the air hose loose from the gear selector, cap it, and air back up. Does it still gurgle?