speed-o & radio problems

First started a while ago. Radio would not shut off when doors were opened and keys were out of ignition. Just last week, radio actually turned back on by itself when truck was parked for a while!!!! So, I disconnected the battery and reconnected when we left a couple days later(we were fishing up the gunflint) When we took off that morning, the speed-o read 25mph while we were idling. after stopping for gas and shutting truck off, speed-o went down to 10 mph while idling. Any information would be greatly appreciated. No check engine light has come on or anything else. Truck seems to run fine, other than this.

oh, 2004 Chev 2500HD with 6.0 4X4.

Not sure abt the radio (which is junk IMO), but the speedo problems may be faulty stepper motors in the cluster...common problem for alot of GM vehicles 2002-2005. You can send the cluster out and have them all replaced with an updated design for abt $75 plus shipping. Did my Envoy's through an eBay repairman.

All I can think of for the radio is a faulty ignition switch...many vehicles let you listen to the radio for ~15 minutes after removing the key. That or there is a relay that controls the delayed-off feature. Good luck!

The radio might be junk, it is hooked up to the speed sensor circuit for the speed controlled volume, it may be back feeding the circuit. I would remove the radio from the dash and see if the problem disappears