Transmission suddenly dropping out of gear

[psudano]

I've had no issues with the transmission up to this point. 3 weekends in a row i've had the camper up and down the hills of PA. Suddenly, the Monday after the 3rd trip, cruising down some local roads, the transmission would suddenly drop out of gear. I let off the throttle for a sec, truck picks the gear back up, and off I go.

 

Started maybe once in 30 miles, and after several days, it happens every couple miles. And happens in most mid-range gears. Once it's in 6th on the highway, i'm good for the trip.

 

fluid levels are fine, spin on filter replaced. replaced the NSBU switch because that seams to cause gremlins.

checked all the grounds and checked thru all the wiring for chafing and could find nothing

 

the only code i get is an intermittent u1016 code

 

any help out there???

[psudano]

Should have also mentioned it's a 2005 Duramax with a 6 speed allison transmission with about 220,000 miles on it.