b34tgnu2

Just curious what rpms are you at when your are doing 75mph?

aliass24

My truck is between 1950 and 2000 rpm at 65 with 275/55/20 tires and 4.10's. I will check for you at 75 on my next outing.

b34tgnu2

Cool thanks. . I have the same size tires with 3.55 and im doing 77ish at that rpm

Al Kohalic

With 4.10 gears, a tire diameter 31.91 inches(275/55/20), and a 6th gear of 0.69:1 these are what the engine rpms will be at the following speeds.

55 mph - 1,638 rpm
60 mph - 1,787 rpm
65 mph - 1,936 rpm
70 mph - 2,085 rpm
75 mph - 2,234 rpm
80 mph - 2,383 rpm
85 mph - 2,532 rpm


(Axle Ratio x Vehicle Speed x Transmission Ratio x 336.13) / Tire Diameter{in inches} = Engine speed

mechanicboy

So did we find out that ford misprinted that the eco had a .61 6th?

My question is, why do you want the 4:10 gears, plan to tow heavy loads often? If not then 3.73 is a better gear.

Al Kohalic

Yes, the 0.61:1 6th gear for the EB 2011 models was a misprint per Ford. The 6R80 only comes in one gear configuration only and does not change with models or engines.

If a 3.73 Eco can handle towing 10,000lbs up the Ike Gauntlet like it did besting a 420hp 460 lb-ft 6.2L with 3.73s then I wonder what 4.10 gears would have done.

mechanicboy

I thought the same thing! It was a heavy, big wheeled version too.

sweetquarter farm

Right, unless your running 35" tires and plan on max tow, 4;10's are hard to justify. 35's and 4;10's end up real close to same RPM as stock tires (32) and 3;73.

the beauty of the ecoboost is the low RPM torque, so know need to turn up the RPM unless your under heavy load.

acadianbob

I wouldn't do 4.10s unless you are pulling very heavy loads very frequently.

I'm pulling a 5,500 lb RV trailer with 3.73s and it rarely comes out of 6th gear.

b34tgnu2

No I haven't towed anything at all actually would like to though haha. Actually I just thought I would 4.10 for the enhanced acceleration. I know turbos like a little less step if a gear for all out performance but that's in cars as far as im concerned cause they aren't 5600# beasts either.