What could cause my standard transmission to gear down on it's own? on 1994 Dodge Ram 2500

When driving on the highway, the transmission will jump from 5th to 4th on it's own.

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3 answers 1 comment
Do you have an overdrive switch for this transmission? Is it possible it is shifting out of overdrive?
Sounds like a synchro gear is bad.
check brake light switch on fuel petal it down shift when you hit brakes
had same problem and sometimes it took very high rpm s to get it to shift up. took it to a transmission shop they replaced 2 sensors in the transmission. $300 bucks. 2000 miles later it started doing it again..it ended up being the computer (ecm) and i never had that problem again.