My truck has a 4.11 gear-ratio differential, but shop manual configuration tables say 4.10 was also available. Just curious what would motivate Ford to make two different third members w/very, very close ratios, but not quite the same? Seems like common sense would say to manufacture one or the other, not both. I think the rear axle shafts might come in two different spline-number configurations. Might that have something to do w/it?
maybe the 4.11 and 4.10 weren’t from the same manufacturers
All I know is that truck manufacturers often have rear ends from more than one manufacturer, even for the same model year and GVWR
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Agree with @db4690s thoughts and I’ll suggest another…
Quiet set and strong set of gears. Gears run quieter if they have more smaller teeth on the ring and pinion but you lose strength. A coarser set is stronger but noisier.
The 9 inch was used in both cars and trucks and you can guess which set went where.
Since the number of teeth on both the pinion and ring must be a whole number (no 11 1/2 teeth allowed!) the ratio may end up 4.11 for the fine set and 4.10 for the coarse or the other way around.
So Ford has a choice which they use on what application. Maybe the quiet goes on small V8 2wd 1/2 tons and the coarse on big block 3/4 ton 4WDs.
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The Ford 9" rear axle was available with 4.11 axle ratio.
The Dana/Spicer 9 3/4" full floating rear axle (F250, F350) was available with 4.10 axle ratio.
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Another one that will get you,
It’s possible to have 4.10’s in the front and 4.11’s in the rear on the same truck.
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I wouldn’t think so, but I suppose anything is possible “in theory”.
I found both the 4.10 and 4.11 gearsets online. The 4.11 has a 9 tooth pinion and 37 tooth ring gear for a 4.11 ratio. The 4.10 has a 10 tooth pinion and a 41 tooth ring for a 4.10. 4.10 has more teeth. The 4.11 ratio is the one listed by racing gearset manufacturers… fewer teeth, stronger gears…
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Thanks for saving me the trouble of figuring out which tooth. combinations worked!
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IIRC the theory was that since you’re only supposed to use 4WD on loose/slippery surfaces that had a lot of “give” anyway, it would be beneficial for the front wheels to have a slight bit of “pull” over the back wheels. The slippery surface that you were supposed to be driving on would negate any driveline binding, again, in theory.
Ford also used a 3:08 and a 3:07 gearset; the latter which I have in my Lincoln.
On a related note, Subaru also uses a different ratio between the rear and front differentials. It’s not much (maybe a hundredth) but it’s designed that way.
some people prefer even numbers, thus the 4.10. Those folks would rather walk instead of driving a 4.11, but then- we are talking Ford so walking is a likely event anyway.
Dodge also did it, at least in the 82 Ramcharger
Chrysler 8.25" rear - Dana 44 front
3.55 rear - 3.54 front
and
3.90 rear - 3.92 front
and
4.10 rear - 4.09 front
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Makes sense to have a higher numerical ratio in the rear of 4wd.
Sketch a 4 wheel vehicle with the wheels turned…the front is farther from the turing circle than the rear and should travel farther to reduce scrub so it needs a lower numerical ratio.
That could be the reason.
I also wonder if the reason for the minor difference in front vs rear ratios is to eliminate any front-to-rear drive-train slap when driving straight.
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Good thought! The front pulls the rear a little bit.
FoDaddy caught onto that a little earlier…