Tranny Problems

I have a 1990 caravan with 157.000 on it the motor was replaced before i bought it i found this out when i had alternator problems and the reason was they replaced the motor but forgot a ground strap. Cost 395.00. This time when i get in my van and start it up it handles good goes in reverse and drive perfectly.If i travel 12 miles or so it will not go in reverse but will go in drive i can bring it home and park it for a while and it will go in reverse i can drive it short distances and have no problem but on trips around 10 + it will do it again?? Ther is no idiot lights that show up on dash or panel.

I have a 1990 caravan with 157.000 on it the motor was replaced before i bought it i found this out when i had alternator problems and the reason was they replaced the motor but forgot a ground strap. Cost 395.00. This time when i get in my van and start it up it handles good goes in reverse and drive perfectly.If i travel 12 miles or so it will not go in reverse but will go in drive i can bring it home and park it for a while and it will go in reverse i can drive it short distances and have no problem but on trips around 10 + it will do it again?? Ther is no idiot lights that show up on dash or panel.

Do you know if the trans oil and filter have ever been changed ?
Mine started doing funny things like not changing gear and I had to pull over and shut it off, start up and go again then it would be fine for a while then do it again. I ended up having to rebuild the box at $1500.