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Something isn't adding up unless you have teeny tires on your rig.
My truck has 265/75R16's with 3.73 ratio gears and 70 mph cruise is barely over 2000 rpm. The 235/85R16's (the other stock size) are the same exact rolling diameter. My truck is a 6-speed, but the engine rpm should be the same in OD with an auto tranny.
I don't think that you need to change gears to 4.10's. The gear vendors OD unit should work just fine.
First truck -- 1929 Model A Ford pickup, restored from ground up. Wish I still had it!
99.5 F250 PSD Supercab LB 4x4, ZF-6 w/SB Con OFE, 3.73LS, Boost & pyro gauges, Swamps S175/146 injectors, DP 80 HP Econo PCM (classic version
), AIS, coolant filter w/"hokum" bracket,
regulated return, heated mirror mod, lighted cupholder, Marinco heater plug-in.
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