My brother-in-law just dropped off his 99 Ram 1500 at my house today. Said the trans was slipping really bad and it's making a bunch of noise when it is in gear. He said this all started suddenly 2 days ago. I think he changed the fluid and maybe the filter yesterday, but I'm not sure.
I've read that there are some key components that can fail on these, but can't find out information to narrow down the issue.

First things first do I check fluid in neutral with trans warmed up? (I'm afraid to warm this one up...) Top off with ATF+4?

The noise from the trans sounds like a buzzing sound, not sure what it is yet.

 

The "buzzing" the pump is bad ,time for a rebuild............