2001 Dodge Ram 2500 4x4 5.9L gas,

Yes, the Map sensor would control the vacume pressure responsible for shifting.

Yes, the Map sensor would control the vacume pressure responsible for shifting which is part of the process taking place up at the throttle body

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Those trans don't shift on vacuum. They are fully electronically controlled and throttle position is transmitted by a cable from the throttle body to the trand. It probably needs the shift solenoid/ transducer/lock up solenoid kit replaced. Done quite a few myself.

As a side note, NEVER has Chrysler used vacuum to shift a trans

I have a 2001 dodge ram van 5.9L but missing my emissions sticker, any chance you could provide what your is for its the same year and engine size as mine? I need to replace the damn cats to pass smog please help!