Very confused on gear ratio?

[TheManOutside]

The 4.56 gears are rare. They only came on 4 cylinder 4Runners with the e-locker. Don't hold your breath to find them.

Oh. Haha well ok I guess that's out of the picture, since I have a v6 and would need a v6 donor. Thanks for this infoOoOo

 

[ShooterMcGavin]

Oh. Haha well ok I guess that's out of the picture, since I have a v6 and would need a v6 donor. Thanks for this infoOoOo

Someone else would know better than I, but I think you can use the 4.56 gears in yours even though you have the V6.

 

[TheManOutside]

Someone else would know better than I, but I think you can use the 4.56 gears in yours even though you have the V6.

Well, I would be able to use them, the only problem is I am going to convert my truck to 4wd, which would require a transmission with the v6 bellhousing, limiting my donor options to the v6 models only. If the 4.56 gears only came with v4's, then they would be out of my "option zone", if that makes any sense. You are right though!

 

[D Farms]

all the trucks had the same transmissions, the difference for a 4wd is the transfercase, drive shafts and the front differential, and also the electronics. all 3rd gen rear diffs and front diff are basically compatible.

 

[Scramble]

Oh. Haha well ok I guess that's out of the picture, since I have a v6 and would need a v6 donor. Thanks for this infoOoOo

I have 4:56 gears & no locker. They are out there.

 

[TheManOutside]

I have 4:56 gears & no locker. They are out there.

Really? huh. What size tires do you have, and how do you like your gears? Did you get them off a wrecked 4runner/Tacoma?

 

[Scramble]

Really? huh. What size tires do you have, and how do you like your gears? Did you get them off a wrecked 4runner/Tacoma?

They came stock on my truck, maybe because I have a 3RZ 5-speed with 16" wheels. It's all I've ever known LOL. My truck is weird, it's a fully loaded base model with everything except leather, sunroof & E-locker.

I ran 275/70/R16's for 10 years & had no problem doing 80mph on the highway. Last year I ran 265/70/R17's with no problems (except vibration issues from the driveshaft & the steering rack so I never really tried cruising at 80) but it did fine at 70-75. My 33's are new so I really cant comment on them yet. After I adjust/grind my UCA's & put in a new CV axle I'll let everyone know how it is.

 

[Scramble]

Really? huh. What size tires do you have, and how do you like your gears? Did you get them off a wrecked 4runner/Tacoma?

I only found out I had 4:56 gears a few months ago & I've had this rig for 16 years! LOL I assumed I had 4:10's & figured the the locked version of my truck came with the 4:56's. Locked Limited's come with 4:30's & aren't that easy to find in the junkyards either. 4:10's are the most common. I'm no expert on Diff's but I did stay at a Holiday Inn last night. :laugh:

 

[TheManOutside]

I only found out I had 4:56 gears a few months ago & I've had this rig for 16 years! LOL I assumed I had 4:10's & figured the the locked version of my truck came with the 4:56's. Locked Limited's come with 4:30's & aren't that easy to find in the junkyards either. 4:10's are the most common. I'm no expert on Diff's but I did stay at a Holiday Inn last night. :laugh:

Wow. 16 years?? Congrats man :bravo: It's still going strong, I'm guessing? How many miles do you have? I find it extremely awesome that you still have it.

As for the diff stuff, I'll see what I can find, but I'll probably end up getting 4.1's, seems like those are the most common.. Also, how bad is it driving with a lower number gear ratio with ~33 inch tires? Are there vibrations, is it sluggish, etc.?

 

[D Farms]

i have 35s on 3.90s and its ok around town, but sucks on the highway if there a lot of hills. on a flat road though its great, 75mph at like 1900 rpm.

 

[TheManOutside]

i have 35s on 3.90s and its ok around town, but sucks on the highway if there a lot of hills. on a flat road though its great, 75mph at like 1900 rpm.

Ok, so I'm not 100% sure if I'm correct or not so bear with me...

You get a higher gear ratio to accommodate bigger tires because with a higher gear ratio, the lower your actual gears, which essentially lowers your RPM at high speeds, giving you less aggressive performance and better MPG...? Is this right, or am I extremely confused and on another planet?

This is what I've got I guess. I could've nailed it, I could be completely wrong haha. idk!

 

[D Farms]

no i just have the stock gearing for the 4wd with 15" wheels. the ideal gear ratio for 35s is 4.88 but a lot of people get 5.29s for the extra torque. in theory i can get better gas mileage, but because it downshift on hills i get worse gas mileage.

 

[csp]

You get a higher gear ratio to accommodate bigger tires because with a higher gear ratio, the lower your actual gears, which essentially lowers your RPM at high speeds, giving you less aggressive performance and better MPG...? Is this right, or am I extremely confused and on another planet?

This is what I've got I guess. I could've nailed it, I could be completely wrong haha. idk!

If by higher gear ratio you mean a higher number, yes it's considered a lower gear.

A 3.90 ratio means that the engine turns 3.9 times (with the trans in a 1:1 gear) for every tire rotation. A 4.30 ratio means the engine turns 4.3 times. More engine rotation for a given tire rotation means the engine is in an RPM range where it makes more power/torque.

A higher number means the engine is turning more RPMs at a given speed, but remember that a larger diameter tire needs fewer rotations per mile, so if you go with bigger tires that plays into the equation as well.

When using the terms higher and lower you need to distinguish if you mean higher number or higher ratio. They are the opposite of each other.

 

[TheManOutside]

If by higher gear ratio you mean a higher number, yes it's considered a lower gear.

A 3.90 ratio means that the engine turns 3.9 times (with the trans in a 1:1 gear) for every tire rotation. A 4.30 ratio means the engine turns 4.3 times. More engine rotation for a given tire rotation means the engine is in an RPM range where it makes more power/torque.

A higher number means the engine is turning more RPMs at a given speed, but remember that a larger diameter tire needs fewer rotations per mile, so if you go with bigger tires that plays into the equation as well.

When using the terms higher and lower you need to distinguish if you mean higher number or higher ratio. They are the opposite of each other.

Yes, I meant higher gear ratio number, I just forgot that part :ybrick:

So basically (in as little words as possible):

Higher Gear Ratio NUMBER -> Less tire rotations per mile (good for bigger tires)

That's as simple as I can imagine. Is this technically correct?

 

[D Farms]

with a higher gear ratio the engine makes more rotations per mile. with bigger tires the engine makes les rotations per mile. so in order for a truck with big tires to make the same rotations per mile as a truck with small tires, the gear ratio must be increased.

 

[Konkordmusk]

with a higher gear ratio the engine makes more rotations per mile. with bigger tires the engine makes les rotations per mile. so in order for a truck with big tires to make the same rotations per mile as a truck with small tires, the gear ratio must be increased.

No, a low gear ratio would be 5.29 or 4.88, and would cause the engine to make more rotations per mile. A high gear ratio would be 4.10 and similar, and would cause the engine to have fewer rotations per mile.
Going to a lower (numerically higher) gear will increase your RPMs at a given speed but improve your off the line performance. A higher (numerically lower) gear will get you off the line slower but keep your RPMs lower at a given speed.

 

[ShooterMcGavin]

If by higher gear ratio you mean a higher number, yes it's considered a lower gear.

A 3.90 ratio means that the engine turns 3.9 times (with the trans in a 1:1 gear) for every tire rotation. A 4.30 ratio means the engine turns 4.3 times. More engine rotation for a given tire rotation means the engine is in an RPM range where it makes more power/torque.

A higher number means the engine is turning more RPMs at a given speed, but remember that a larger diameter tire needs fewer rotations per mile, so if you go with bigger tires that plays into the equation as well.

When using the terms higher and lower you need to distinguish if you mean higher number or higher ratio. They are the opposite of each other.

Well said.

Higher Gear Ratio NUMBER -> Less tire rotations per mile (good for bigger tires)

Gear ratio has nothing to do with the number of tire rotations per mile. The tire rotations per mile is a factor of the circumference of the tire. Tires with larger diameters have larger circumferences, and therefore cover more distance with each rotation. A larger tire will rotate less times per mile than a smaller tire.

Gear ratio has to do with the number of engine rotations per rotation of the axle. A higher gear number means that the engine turns more times for each time the axle turns. Since bigger tires cover more distance per rotation, increasing the gear ratio number means that the engine can turn at the same speed for the vehicle speed.

 

[ShooterMcGavin]

No, a low gear ratio would be 5.29 or 4.88, and would cause the engine to make more rotations per mile. A high gear ratio would be 4.10 and similar, and would cause the engine to have fewer rotations per mile.
Going to a lower (numerically higher) gear will increase your RPMs at a given speed but improve your off the line performance. A higher (numerically lower) gear will get you off the line slower but keep your RPMs lower at a given speed.

This is all true. As you suggest Konkordmusk, we should start using proper terms. Higher gears are lower numbers. An effective ratio of 1:1 means that the engine turns 1 time for every 1 turn of the axle.

The numbers we are talking about in this thread are rear differential ratios. Ratios are read as inpututput. So, if the drive shaft turns through 41 rotations to turn the axle 10 rotations, we have a rear end ratio of 4.10:1. That does not take into account the transmission or transfer case though, so that is not the final drive ratio.

 

[Konkordmusk]

This is all true. As you suggest Konkordmusk, we should start using proper terms. Higher gears are lower numbers. An effective ratio of 1:1 means that the engine turns 1 time for every 1 turn of the axle.

The numbers we are talking about in this thread are rear differential ratios. Ratios are read as inpututput. So, if the drive shaft turns through 41 rotations to turn the axle 10 rotations, we have a rear end ratio of 4.10:1. That does not take into account the transmission or transfer case though, so that is not the final drive ratio.

Agreed. I have always referred to numerically higher gears as shorter gears, and numerically lower gears as taller gears, to prevent confusion. But that might just be me!
However, the rear end ratio IS actually the final drive ratio. It's not possible for the driveshaft/axle shaft ratio to change, ever. No matter what goes on in the transmission, the rear differential ratio is the final drive ratio, since it cannot change.

 

[ShooterMcGavin]

Agreed. I have always referred to numerically higher gears as shorter gears, and numerically lower gears as taller gears, to prevent confusion. But that might just be me!
However, the rear end ratio IS actually the final drive ratio. It's not possible for the driveshaft/axle shaft ratio to change, ever. No matter what goes on in the transmission, the rear differential ratio is the final drive ratio, since it cannot change.

Ahh, yes. I see what you mean. I meant to refer to the complete sum of all ratios from the flywheel to the axle. I suppose "final" ratio means "last"? I was under the impression that "final" ratio meant the sum of the ratios, in one specific gear. Is there a term for that?