I've got a 3.1 auto and I'm considering changing from a 3.23 ratio to 3.73 (maybe 4.10) for auto-x.
Now at 2k rpm in OD the car does 65mph. At 2k rpm I calculate with 3.73 it would be 55mph and with 4.10 it would be 47.5 mph. Can anyone confirm I got the math correct? Also, 4.10 would be terrible for the open road but would it be a good idea for auto-x?
As for adding posi I've seen Eaton, Strange, Powertrax etc. etc. and cone and clutch types. Any recommendations as to which one is best performing and best value?
I've looked into getting a used rear end but with the cost plus shipping or drive to pick up it's still up there in price and it's used. Also would only need to remove diff cover. I think. Any opinions greatly appreciated.