I made a trip approx 150 miles each way towing a trailer.I had overdrive locked out and towed just fine on the way back my trans lockout light on gear shift started flashing and now does not work what would cause this.

Another problem I have with this tranny is a very hard shift from 1st to 2nd.shfting to 3rd and OD is just fine what would cause this hard shift.

 

A problem caused the hard shifting. The only way to find out what that problem is would be to get the codes read. When the OD light flashed a code was stored. It will stay there for about a month.

 

The hard shift from 1st to 2nd has been present since I bought the truck 7 months ago. It did not start when the OD light started flashing.

 

Mark it also shifts from 1st to 2nd at about 15 mph.

 

That's probably a problem in the 1-2 shift accumulator. That can be accessed by dropping the pan, the trans does not need to come out.

But you still need to get the codes read to find out what's wrong. If you ignore the flashing light it's almost guaranteed that you'll need a new trans soon.