4.10 rear in new Ford F350
A lot of leftovers have the 4.10 rear any one know if there would be a big difference in MPG towing or would it be negligible..?
Forum Discussion
Lynnmor wrote:Me Again wrote:
. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!
Keep in mind that the transmission is worked harder with higher diff gears.
You multiply the top gear ratio times the diff gear ratio, and the result is always more torque with the lower rear gears. Add to that, each gear change is less of a difference in road speed, keeping the engine at a better RPM.
That basically applies in first gear to get a load moving.
Out on highway one is in 5th and the other in 6th at the same speed. You are dismissing a taller 6th gear od ratio. That is why I say the final gear ratio of the 4.10 truck in 6th is similar to the 3.42 in 5th. Both have enough lower gears. The Aisin has a deeper 1st and 2nd gear over the 68RFE. In the 4.10 truck the 1st gear is almost a waste, and some users would like to be able to lock it out. In the 3.42 truck you have a freeway cruiser in 6th, 80 MPH is only 1750 RPM and around 19 MPG.
I would have bought a 3.73 ratio if it was available, however at 60K on the clock and 4 years I am quite happy with 3.42 gears. We did two round trips from the NW to Arizona at 24,500 lbs combined and that combination worked well. We now commute back and forth with a TT at 16K combined.
I owned a truck with 4.10's and .69 OD for 14 years and a freeway cruise is was NOT. It towed fine however. It was gear bound with only 4 forward speeds.
