What is this part, please help

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What is this part, please help

January 28, 2020, 08:18:00 pm

This part is leaking air. In Puerto Penasco so this diesel mechanic was trying to chase down air leaks. A bit of a language barrier. Any help in identifying this part would help greatly. He seemed to think the hose at the other end was headed to the transmission??

Thanks in advance for your help
Tommy

Re: What is this part, please help

Reply #1 – January 28, 2020, 08:40:47 pm

That is an air valve for the retarder. I will see if I can get a number.

Allison retarder air valve

Re: What is this part, please help

Reply #2 – January 28, 2020, 08:55:31 pm

Thank you sir, it was great to meet you at Quartzsite. Hope you had safe travels home!

Re: What is this part, please help

Reply #3 – January 29, 2020, 05:05:48 am

Tommy,

Part numbers for you if you can't clean up the one you have
Old Allison part# of 29522717 there was another old number but don't have it handy at the moment.
New Allison part# of 29552377

Mike

Re: What is this part, please help

Reply #4 – January 29, 2020, 10:04:19 am

Looks like this is all I can find without buying 50 of them.

ALLISON 29557354 VALVE ASSEMBLY-SOLENOID RETARDER | eBay

Re: What is this part, please help

Reply #5 – January 29, 2020, 11:45:33 am

Thanks for your help, I think I will attempt to rebuild when I get home. This part seems to be the biggest culprit to my overnight air loss. Please further my knowledge, I know what the retarder does and how to use it. What is this parts job? I have no current problem maintaining air pressure, am I ok to return to KY before attempting rebuild?

Thanks again for all the help!

Re: What is this part, please help

Reply #6 – January 29, 2020, 12:00:50 pm

Interesting... who would have thought the transmission needed air. Good write up on how to clean it. I too would like to know what this part does.
Bob

Re: What is this part, please help

Reply #7 – January 29, 2020, 01:49:12 pm

Supplies air pressure to force transmission fluid into the retarder impellers.

Re: What is this part, please help

Reply #8 – January 29, 2020, 03:39:53 pm

I can hear the solenoid exhaust air when I return the retarder joystick back to off. I too was in the dark about where the solenoid was located and what it did. So much to learn.

Re: What is this part, please help

Reply #9 – January 29, 2020, 03:40:08 pm

To expand on what Cman posted.
The cylinder that this valve is mounted to has a piston inside. This piston has seals on it that seals the oil on one side from the air on the other side. When the retarder is activated this piston moves due to the changing air pressure causing the oil to be forced through a set of turbine blades causing drag. Really simple system that hasn't changed much over the years. There is at least one of the first few coaches that had a retarder that this piston movement was done through a manual hand valve mounted below the dash. Now we have the rheostat that has 6 places and is what you would call a fly by wire system.

@ Tommy, You can drive from now own without using the retarder. If you have an air loss through this valve you can just plug the air line that feeds the air valve and continue on. The transmission don't need air to operate only the retarder.

Mike

Re: What is this part, please help

Reply #10 – January 29, 2020, 09:00:15 pm

I have the retarder as well. Never knew til now what actuated it and made it work. Not only do I now have a description, I have a picture. Further how it works. The forum is indeed a wonderful thing.

Re: What is this part, please help

Reply #11 – January 29, 2020, 09:03:17 pm

Thanks craneman and Mike for the explanation.

Re: What is this part, please help

Reply #12 – January 29, 2020, 09:05:38 pm

Quote from: steve31 – January 29, 2020, 09:00:15 pm

I have the retarder as well. Never knew til now what actuated it and made it work. Not only do I now have a description, I have a picture. Further how it works. The forum is indeed a wonderful thing.

On a 1990 U300, I suspect you do NOT have a transmission retarder-- at least, not a OE equipment.

Likely you have an engine compression brake on your Detroit Diesel 6V92.

Re: What is this part, please help

Reply #13 – February 06, 2020, 09:46:17 pm

Quote from: wolfe10 – January 29, 2020, 09:05:38 pm

On a 1990 U300, I suspect you do NOT have a transmission retarder-- at least, not a OE equipment.
Likely you have an engine compression brake on your Detroit Diesel 6V92.

As usual Brett is correct but your switch on the dash is labelled Retarder. It is really a Jake Brake (if it's a DD 6v92). It's a 3 position switch Off, 3 cylinder, 6 cylinder. I have tried the 3 cylinder and don't really notice anything more than OFF position. I leave on 6 cylinder all the time.

see ya
ken

Re: What is this part, please help

Reply #14 – February 06, 2020, 10:28:13 pm

Quote from: kenhat – February 06, 2020, 09:46:17 pm

I leave on 6 cylinder all the time.

Go BIG or go home!

Re: What is this part, please help

Reply #15 – February 07, 2020, 12:36:17 am

I think that without a working air activated retard cylinder, transmission retarder will still work.

Activating the retarder with brake pedal or joy stick, tells transmission to divert some tranny fluid into retard to slow coach.

The big separate retarder cylinder being talked about in this thread gets the fluid moving quickly, sort of an initial push. Without it things work the same, but with slow start.

This is my understanding, so capping off a leaking air line, should still keep retard working.

Re: What is this part, please help

Reply #16 – February 07, 2020, 12:36:46 am

Well gentlemen 1990 was a strange year for GV coaches. Folks who know a lot more about Fore travels than me last year at Quartzite determined mine was a hybrid of 89, 90, 91. The original owner called the shots on how he wanted it built. I have the 6V92 and it definitely has a retarder. There is a switch on the dash, a simple on or off. I do not have the joy stick arrangement. Retarder comes on when I apply the brakes. You can feel it when it does. I have a temp gauge built into the dash ( OEM?) that tells me temp of the transmission converter. I keep it below 300 degrees on long downgrades. Temp can go up FAST so keep an eye on it. My OM had Jakes on every Freight-liner he had and I got my class 1 at age 16 so yes I know the difference. Even learned to blip the Jake to reduce engine RPM's on a hill so I could pick up another gear without losing road speed. Only problem with that is if you missed the shift you were doomed. Almost came to a complete stop on the Carcquinez bridge after missing one doing that and then not being able to find a slot to get it back in gear. VERY embarrassing. I hope you have all the manuals for the coach. If not I will be happy to copy what I have and send it your way. My book has a pretty detailed explanation of how to use it properly.

Re: What is this part, please help

Reply #17 – February 07, 2020, 12:52:21 am

Quote from: Barry & Cindy – February 07, 2020, 12:36:17 am

I think that without a working air activated retard cylinder, transmission retarder will still work.

Activating the retarder with brake pedal or joy stick, tells transmission to divert some tranny fluid into retard to slow coach.

The big separate retarder cylinder being talked about in this thread gets the fluid moving quickly, sort of an initial push. Without it things work the same, but with slow start.

This is my understanding, so capping off a leaking air line, should still keep retard working.

I might be wrong, but that retarder valve is the only way I know to push the fluid into the retarder turbines. I will follow this thread and correct if I am wrong.

Re: What is this part, please help

Reply #18 – February 07, 2020, 02:03:20 pm

1990 U300 had a automatic retarder. Brake applied. Impressive demo ride. Switch on. Heavy braking. Brace yourself

Re: What is this part, please help

Reply #19 – February 07, 2020, 03:42:21 pm

I think the discussion turned on a wrong branch. Tommy's GV is a 2000 (yup, one of those unicorn GV 320's with a slide out).

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