It's a manual. Are the 4.10's still a good choice? I do highway driving everyday to work.

 

5th gear is a wide range gear. i think MD said it was a 20% increase in rpm with 4:10 and a 13% increase with 3:73. just figure in your calculator your rpms in each gear and thats what your rpms will be. 2000 + 20% = 2400 rpm 3000 + 20% = 3600 rpm 4000 + 20% = 4800 rpm 5000 + 20% = 6000 rpm

 

you also can go with 390s(389) if you want a little more than 373 but want to save fuel milage over the 410s
alot of people dont know about them

 

I guy that use to work with me put 4.30 in his 4.6 auto. He said not much of a difference in rpm on the highway, but a huge difference in power when you step on the gas.

 

If you were doing a lot a freeway driving, ~130 miles at 85mph and ~130 miles at 95mph all non stop one way. Then back home again two days later and this occured every two to three weeks. Would you feel comfortable with 4.10's running 2990rpm tht long or 3.90's running 2750rpm's that long or would you do the 3.73's? (2003 Mustang GT)

I'm leaning towards the 3.73's.

 

I knew of the 3.90's, but I figured that 3.73's and 4.10's were the most popular for any given reasons. I think when I swap, I'll do 3.73's. 4.10 would be too much gear for me on the highway, especially since I take long trips for vacations.

 

Someone told me that 3.90's have to be shimmed EXACTLY right or they will chew them selves apart in a matter of days.

 

I expected a big change in my car when I picked it up from getting the 3:73 put in, (thats one job I wont attempt) I was dissapointed, not a huge difference. Go 3;90 or 4 ;10 , I did pick up .4 in the 1/4 though.