Regearing the rear end

[bigdiesel99]

4.10's is enough to get a big 5er and F550 going? I'd think that'd be like towing with my truck w/ 3.28's or something.

Hope it works out for you!

550's have the same 7.3L powerstroke and same 4R100 tranny, a 4:10 is the same in the S135 axle in the 550 as it is in the 10.5 used in 250's and 350's the only difference is strength and load capcity. a 4:10 is plenty.