Gear strength vs. ratio

roachie

roachie

Taco Master
I cant remember what I learned about this years ago. If you keep all forces equal and only change the ratios. How does a high ratio (3.08ect) compare to a much lower one (4.30)? The higher ratio would have more tooth contact area but, wouldn't that generate more heat? Or am I just all to wrong?
 
Also the higher ratio your asking each tooth to do more, and the larger bite has a tendency to try to spread the ring and pinion apart.
 
I think they would be ok, I saw issues with 3.54 and carrier bearing spinning in a puller.
 
Strength should't be an issue, I see very few numerically high gear sets fail. Might be because of the larger contact area which may help more evenly displace heat and load. Might also be because " stock" gears a generally not abused.
 
a numerically higher r&p has a smaller diameter pinion, each tooth on pinion has to work more.
for example, a 3.0:1 pinion has to work half as much as a 6.0:1
but, as the number goes up, the torque input is also increased out, as there is more leverage applied.
also generates more heat and cant dissipate it or absorb it as fast as a numerically lower r&p. also the ring gear grows in thickness accordingly the higher you go.
 
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These are OEM Ford gears, I just dont want to drop the ratio back down after I spent the coin on these.
 
you should be good man, alot of the 6.7s come with 3.31s stock, set up for towing

I wouldnt think twice about it
 
meh.... i dunno lol, be gentle...

i still dont think i would worry about it i think i would be worried about the driveshaft first.
 
Don't want to derail the thread but I have to ask, what over drive ratio is the tranny behind the Ford 6.7s?
 
What was your price on the 3.31's? I'm looking to put a set in my 12v excursion with a G56. I have a 10.5 and a swapped in dana 60 front. Do you have the part #'s and special install stuff needed specific to those gears?
Thanks,
Deo
 
I think the install kit for the rear was $500 through randy's ring and pinion with genuine ford gears. I cant find them for the front, though I havent really looked hard for them.

From experience, the 3.31 gear needs a 6 speed in front of it. My nv4500 with these and 33's are just about useless.
 
In my first gen, I am used to 3.07s and a getrag 360 5 spd, with 285's ..I like the set up ..Tow in 4th direct etc .... heck in 4low you can still drive 50 plus mph lol......only problem dropping gears on a hill the spacing is a little wide...
Thanks
Deo
 
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