OK, I know I could probably find the answer with search, but I'm still at work and don't have time to run it.

My brother-in-law's '99 3500 auto 4.10 is starting off in drive. If he pulls the shifter down to 1, it will start in first and he can shift manually up through the gears, till he gets to Drive. But it won't go into OD. Just started acting up this afternoon while he was out and about.

Where does he start looking for the problem?

 

OK, problem resolved...

Transmission relay in the PDC went bad. Swapped the Security relay in it's place and everything is back to normal.

 

I was just about to say that it's a solenoid or relay. Mine have gone out once.

 

He said the trans relay was hot when he checked it, so it must have shorted internally. So he's half glad it was an easy fix....the other half was hoping it was tranny upgrade time.