Transmission air modulator? - Printable Version

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+--- Thread: Transmission air modulator? (/showthread.php?tid=7151)

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Transmission air modulator? - BusNit - 01-02-2023

Not sure what this is called but I have been cleaning the underside of the bus the last couple of days. Today while continuing on my degreasification, I heard and felt bubbling in the transmission oil pan. I believe this fitting is leaking air into the transmission. I have my 120v compressor on so the system is always pressurized. One of the great things of having a pit is finding crap you would never had known was at fault! The piece in question is where the blue air line goes into.


Edit:

After a couple hours of research and cross referencing, I found the part. For those of you with the HT740 transmissions, this is a Williams Controls air modulator. Part number is WM775B or 117830. Prices range from a low of $60 to a high of $407. Found a new one on eBay for $160 delivered. Most places were out of stock or you had to call to see if they were available.

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RE: Transmission air modulator? - HoosierDaddy - 01-03-2023

My 110V compressor cycling dropped considerably after I replaced that part!!! I kept hearing a bubbling sound near the engine bay when it was sitting in my shop and all was quiet. I finally found the culprit!

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RE: Transmission air modulator? - BusNit - 01-04-2023

I am at 22 min cycles. There is a minor airbag fitting leak at the front. Leo will tighten that up when I go back but any air leak found is a good one! It's like scratching an itch good! I don't know what would happen if the modulator would fail. Leave you stuck in 1st gear?

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RE: Transmission air modulator? - BusNit - 01-08-2023

Modulator was replaced. I did not drain the transmission fluid but instead swapped it out as quick as I could with my thumb over the hole. Lost maybe 4-6oz of fluid and most of it down my arm. Needless to say I was a mess along with some splash back off the pit steel rail. It was fun. Pit was a mess from cleaning the bottom side. Now I am ready to paint once the floor of the pit dries from washing it down so I can put plastic to avoid an even bigger mess!

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RE: Transmission air modulator? - Latitude 28 - 01-08-2023

Simon,
I can really see how handy your pit has become....a huge time saver!  Think about how long it would take jack, support, creep your way around under the coach and get the coach back on the ground....super nice setup!

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RE: Transmission air modulator? - BusNit - 01-08-2023

Thanks Steve! I believe the pit already paid itself off from a saved tow/repair bill!

I am happy to say compressor now cycles every 2 hours from 22 min! that's some serious transmission fluid aeration! I haven't driven it yet but does go into forward and reverse. I'll keep chasing those air leaks

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RE: Transmission air modulator? - HoosierDaddy - 01-08-2023

Some days I am in my shop next to the MH so I can hear the compressor. Typically it cycles once per day. I don’t know if it cycles during the night or not? That is down from 30 minute cycles a couple years ago!?

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RE: Transmission air modulator? - BusNit - 01-08-2023

Any tips on what you found that was leaking? By the way, I sent out the refrigerator door seals. Let me know if you didn't receive them.

All airbags are new. Generator airbags are also new along with regulator. The only thing that I am aware of is the front right airbag supposedly has a minor leak that Leo will get to. I don't think it's big enough to leak down that much. But crap, a whole day would be a dream for me to keep that compressor silent!

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RE: Transmission air modulator? - Jack Houpe - 01-09-2023

Finding an air leak is like getting a Christmas present I'm up to 4.25 hours. A pit would be a very useful tool your a lucky guy! Do you cover it when not in use?

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RE: Transmission air modulator? - BusNit - 01-09-2023

Thanks Jack! Yes, It is always covered with a steel open mesh walkable grid.

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