bike-maker
Full Access Member
Hello all.
I'm currently in the middle of tearing the 460/C6 combo out of my 84 F350 Crew Cab 4x4 for a 7.3IDI/ZF 5 speed. Among the mass of parts I have now acquired, I have the option of either 3.55 or 4.10 gears. I like the 3.55's for fuel mileage since the truck will become my daily driver - 60 miles a day of straight, flat Interstate driving at about 70mph. But I will also be towing a fifth wheel with the truck that weighs about 10k pounds, which makes me lean more towards the 4.10's.
If my math works out, the difference between 3.55 and 4.10 gears @ 70mph is 300 rpm with 33" tires; 1950rpm vs. 2250rpm. Can anyone give an accurate guess of how much this would hurt the fuel mileage? Better fuel mileage is my main reason for doing the swap in the first place.
Thanks, Mike
I'm currently in the middle of tearing the 460/C6 combo out of my 84 F350 Crew Cab 4x4 for a 7.3IDI/ZF 5 speed. Among the mass of parts I have now acquired, I have the option of either 3.55 or 4.10 gears. I like the 3.55's for fuel mileage since the truck will become my daily driver - 60 miles a day of straight, flat Interstate driving at about 70mph. But I will also be towing a fifth wheel with the truck that weighs about 10k pounds, which makes me lean more towards the 4.10's.
If my math works out, the difference between 3.55 and 4.10 gears @ 70mph is 300 rpm with 33" tires; 1950rpm vs. 2250rpm. Can anyone give an accurate guess of how much this would hurt the fuel mileage? Better fuel mileage is my main reason for doing the swap in the first place.
Thanks, Mike