Modulator adjustment - Printable Version

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+--- Thread: Modulator adjustment (/showthread.php?tid=7923)

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Modulator adjustment - rgunderm - 03-30-2024

I have a 1994 Newell 45 with an 8V92 at HT740 Allison. My transmission is shifting late and I’m assuming it’s a modulator air pressure adjustment. Owner’s manual states it is in the passenger side engine compartment but I can’t find it. 

Anyone have any experience with this?  

Coach 349

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RE: Modulator adjustment - MrE - 03-30-2024

Your coach has an ECU, I would suggest getting an engine monitoring system like BlueFire or SilverLeaf. They log any error conditions between the engine and transmission and will tell you what's happening.

Browse through this thread for more information Engine and Transmission Monitoring Systems

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RE: Modulator adjustment - BusNit - 03-30-2024

There is a pressure regulator for the transmission modulator. The modulator itself is a wear item and needs to be replaced at each transmission oil change. Mine was bad and leaking air into the trans fluid. I could hear the gurgling when the coach sat. Pressure I believe is set to 60psi.

To find the line follow the air hose from the transmission modulator (right side) and see which regulator it goes to. There are two pressure regulators on the passenger side engine wall. One is for the tag axle (25-30psi setting) and the other is for the modulator.

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RE: Modulator adjustment - rgunderm - 03-30-2024

Thanks Simon. There are two gauges on the passenger side engine compartment. Bottom one is definitely tag set to 25 per the manual. Top gauge is not connected to a regulator but is set to 90, it is plumbed out of the valve block with no way to adjust. I will email Newell service and see if I can get some sort of diagram.

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