Happens while driving @ road speed . Kinda intermittent deal.when happens tranny wants to downshift.

Cummins turbo diesel, with 345,000 miles, on it

alt is ok also tried to get codes but scanner dos not acknowledge vehicle

would this be transmission solinoid or other? fluid hoses and linkage all are good

O'Riley code says trimming chain has skipped a tooth. ?? How hard a repair is this for a backyard macanic ??

What does it mean when my engine light reads GEN? I've had my truck for a year with little issue other than normal replacement parts. Not sure what this code means, 8th it saying just general engine problem? I've checked other codes only other code I get comes up 32 I know that is either the a problem with the solenoid or air pressure ratio problem

pulled vacuum cable off heat controller.

Fluid and maintinence

Is there a vacuum or electrical connection that tells the hubs to lock?

has no reverse but drives forward normal