Hello everyone!

Hoping someone can help me out with a few transmission questions.

My neighbor has a 2000 Frontier. His transmission has been howling in pretty much all gears except 3rd. Last summer we drained the oil and I ran it through a paint strainer. I found what looked like an outer chrome part of a bearing ball in the strainer. I assume its from a counter shaft bearing since 3rd gear is quiet when under load. We managed to get a used trans from a junkyard last summer as well. I plan to order a rebuild kit for it and have it ready to go and just swap it in his truck when we can. The cast number on his trans just below the shifter area is 5W71C, the used one from the junk yard has the same number. However when I look for rebuild kits they seem to be for a FS5W71C. Is there a difference in these two transmissions?

Thanks