Elmo , there s a site on line called( OnlineConversions ), you put in your particulars and it will give you all the info you want .
For example switching from a 4.57 to a 4.11 will drop your rpm by 300 rpm at 55 mph 2800 to 2500, seems like a lot of effort for little gain .
I agree with Barnfind49 that an O/d gear would be an option although I believe more costly .
Depending on how much driving you do 3000 rpm will give you 58 mph which given a reasonable condition 235 shouldn't bother it.
I had a tired 235 and ran 500 + miles on some days at 3000 rpm with no problems .
P.S that's not noise your hearing , that's music!!
John
