80 GMC Sierra Classic. Transmission slowly shifts.?

[kevin]

Stays too long in 1st gear. when i come to a stop shell jolt real badly, it feel like someone bumped into me from behind. The truck wont go faster than 50 mph. Shes been over heating really bad too. Now ive changed the trany filter already so.....? there were metal shavings in the pan. But this truck was a diesel an the previous owner put a early 80's Oldsmobile 307 in it, the trany is the original stock 350. I just need a few opinions of what could be wrong (other) than the metal shavings.

 

[greedy]

try getting a transmission flush or a tune-up new spark plugs and wires if none of those work u may need new one.

 

[Mike Loch]

does the fluid smell burnt or look black? Im sure the planetar gears are shot along with the front pump. I would get ready to buy a new one