The ses light comes and goes, and so does Rev. Not always at the same time. replaced ns switch, with a tan 1 from allison $81 worked for test drive, now dosn't want to back up to trailer to make money. but may work at other times (like free trips) 2002 2500 hd. any thoughts?

You need to check for trans codes. Could be ign sw. Could be a piece of debris in the valve body that's blocking a feed orifice.

it used to come and go, (like Rev.) but now if you do get rev., it kicks out within 10 feet. checked all plugs, wires, and new nsbu,

thanks guys, found F solenoid tested, good but we replaced it anyway works fine now, FYI found a 24 hour parts place bergeys truck repair. in stock $38