Synthetic Castrol 5 w 30 if Getrag

[SFerrin]

On the advice of this group (reading archives and listening in) I have just changed the oil in my getrag 5 speed. The fluid that was in it was pretty clean and seemed in good shape. I put in Castrol Syntec 5w 30. By the way, my fill plug wouldn't open. I actually torqued it so much it started to deform the inside of it, so I quit. I just used one of the upper pto bolts and pumped it in there and it worked fine. I think I put in just slightly over 5 quarts. I assume this is OK. I noted in the oil drain jug, that it left behind just a bit of metal shavings. Not much. This has 213 k miles. Is it OK to have just a bit of metal shavings, or am I on the way to trouble. It shifts fine. I've only owned it 3 months so I don't know when it was last changed.

By the way, the manual says to use Castrol Syn"torq" and says to use it only for the NV4500 tranny. I assume you all know more about keeping these older trannies happy than the manual so I put in the synthetic. Everything OK? I only pull a two horse trailer with this. Am I doing right by my rig? By the way, I can tell clear difference between this motor and my other pickukp. In idle and second gear this will go straight up the hill of my driveway. Torque. Can't do that with my gasser.