4r100 help needed, converter?

[melmount]

My wife towed a horse in a 3 horse trailer up to virginia thru some good hills. I just drove her truck today, to fuel it up. The trans seems to be real loud with a whining or like a old hot rod with a flex fan noise. Its loud , no grinding or anything. i floored it and it seems to be slipping, it drives ok but has lost a lot of acceleration. The fluid does not seem burnt. Buts its definately louder then it was last week and its not motor noise. Supposedly trans was rebuilt at one point but that would be at least 80k ago.
How would i know if its just the converter?

[melmount]

clutch fan was siezed up. Dont know why it would of felt slow but fixing that first