Sorry, but you have it backwards. "Shorter" is higher numerically (more torque), while "taller" is lower numerically (more speed). Maybe this is from runners: taller folks can cover more ground with fewer strides, while shorter folks have to wind it up more to keep the same pace.

 

the input gear makes one full revolution, turning the smaller (SHORTER) gear, with less lands, faster than it turns the larger (TALLER) gear. The revolution on the TALLER gear is less, but the leverage is much greater than that on the SHORTER gear, and therefor more torque is available using the taller gear, though more speed is achieved through the short gear..



sorry I had to go all barney..



original poster: just food for thought.. gears are the best SINGLE modification that can be done to these rigs.. however, it is hard to find an installer who can do it right, and it's not a job most folks can do in their driveway.. CAM's, however, when coupled with tuning, intake modifications, and exhaust systems modifications can net you similar gains, and finding someone capable of doing RIGHT it is pretty easy..

messing with engine internals for power gains can cut drastically into the reliability and/or life expectancy of your truck... good gears and good install of those gears won't..

always a compromise, huh?

 

Your illustration is perfect - if you label the gears correctly. In the differential, your "input" gear is the ring gear (driven) and your other two gears (either one, not both) are the pinion (driver). Your "high ratio" would be the shorter gear (higher ratio, 4:56 perhaps) and your "lower ratio" would be the taller gear (maybe 3.55). I didn't count gear teeth, so I'm not sure about the ratios, but the principle is valid.

 

^^ What Mike said, you have them labeled incorrectly.

Just to clarify, the input gear would be the Pinion which is the smallest gear in the differential. The largest gear in the differential is the Ring gear.
So, numerically higher i.e.4:56 would be for better torque but slower top speeds.(rpm's would be higher) While numerically lower i.e.3:55 would be less torque but faster at top speeds.(rpms would be lower)
4:56's are considered a shorter gear because you would cover less distance per revolution.
3:55's are considered a taller gear because you cover more distance per revolution.

I hope that helps you understand better.

 

I assume that you are towing in tow/haul mode??

 

Y'all are giving me a damn headache! Gears and how they pertain to automotive differentials 101:
If someone changes to a higher gear ratio they are actually changing to a numerically lower ratio. If you were to swap a 3.55:1 gearset with a 3.92:1 gearset you would be switching to a lower gear even though the ratio of driveshaft turns to turns of the wheel is higher. If you swap a 3.92:1 with a 3.55:1 you are switching to a higher ratio. I don't how high ended up meaning low numerically or low ended up meaning high numerically, but they do. A car is capable of a higher top speed with a higher gear but at a loss of acceleration, especially in the low RPM range. Lighter vehicles that are meant to do a lot of interstate cruising have higher gears. Muscle cars or trucks meant for hard acceleration, hauling or towing should have lower gears.
A numerically higher ratio will cause the same tire travel but at higher RPM. For example, a 3.92:1 ratio will cause the same tire travel but at higher RPM than a 3.55.
A lower gear (3.92:1) will require a lesser amount of torque than a higher gear (3.55:1) to accelerate at a given rate. A higher gear will require more torque to accelerate at a given rate. Therefor, in vehicles that are identical in every aspect except the gearing, the vehicle with 3.92 gears will give the feeling of having more power than the one with 3.55 gears.


You want to disagree with someone, disagree with me!!!


Oh and in next week's class, we'll be discussing "EFFECTIVE GEAR RATIO"...

 

It's all about torque multiplication!!

Personally, I thing 4.56 gears should have been the standard gears installed with the 20" wheel option and 4.10's with 17's.

 

LOL! Yeah, it never made much sense to me, but it is what it is. Took me forever to remember it's backwards from the logic.

My "effective" gear ratio is about 3.3 with these 285/70s. No wheelies, but 15.6 mpg @ 80 on the interstate. Better if I stay out of the injectors, but where's the fun in that?

 

thank you Hammer.. the input gear (pinion) turns the dive gear (ring), slower in a lower geared (numerically higher) because there are more teeth on it.. in doing so, it increases the leverage on the gear, although the ratio of input revolution : output revolution is lower.. that's where the higher and lower comes from in the first place.. it is referring to the OUTPUT of the gear.. HIGHER ratio gears turn MORE than LOWER gears when compared to the SAME input revolution.. which makes my little pic make sense- and is the reason I posted it..

I'm still waiting for a race between tall and short people to be demonstrated, and how this somehow relates to explaining gear reduction/amplification..

 

Wow a simple post turned into a massive headache.

To the OP - go with the 4.56's, they will give you more lowed (they wont add any, just change how your existing is used). Don't worry about the the mpg's if anything they will go up as you are putting less stress on the engine to get it moving. Don't worry about the lack of top end, you wont notice it PERIOD unless you are attempting to figure out your top speed, then you will see it. Don't worry about high rpms either while not towing, the OD in the transmission will drop it to a much lower overall gear ratio (somewhere around a 3.73:1) so cruising at 70mph the rims are only around 21-2200rpm.

Its great to know the terminology but if you don't know what affect the part is going to have on your vehicle all that means squat.