got this 2000 f550 and a spare trans for it, the spare has brownish trans fluid that smells burnt. What is this indicating? New to the auto trannies so need as much insight as possible, thanks!

 

Burnt fluid means the internal clutch materials burned off due to too much friction from slippage. Overheated the trans most likely, very common problem with the small OEM trans cooler. It's possible that with fresh filter and oil it will be ok. Mine overheated badly back when I first towed with it, but it survived. But yours was yanked for a reason, so I'd either rebuild it, use as a core for BTS/John Woods, or just CL it and take your best girl out to dinner on the proceeds.

 

got it, thank you, am thinking about installing a larger style cooler from a '05 f450, is this the best option for a fairly inexpensive replacement cooler?

 

Yes it is.