While changing the fluid I noticed it was a silvery red color... That can't be good but it don't grind gears at all... What could be the cause of this??????

 

Probably just normal wear to be honest. Especially if it's been in your trans for a long time. Try a short run with fresh fluid to flush it out, drain and refill with a high quality fluid. I'm not a 5 speed expert on these trucks, but that's what I'd try.

 

It's the original transmission with 180,000+ miles on it