What do i gain from taller differential gears??

Ive heard a lot of people talking about swapping out oem gears for taller differential gears ie: 4.88's.
It makes sence to me if youre going to be doing a lot of trail/rock crawling, but what about a daily driver?
I run 32" a/t's on my DD tacoma and it runs just fine, a bit more sluggish than standard size tires but not by a large margin. Also my fuel efficiency has taken a noticeable hit.
Im curious to know what i may benefit from running taller gears.
I would like the option of running 35"s but feel the drag would just be too heavy.
Also, how much would this upgrade cost?

 

In your MPG calcs have you factored in the error introduced to your speedo/odo?

This will help you understand the gear changes introduced by tires and differential changes https://www.tacomaworld.com/tirecalc

A proper gear change will run you around $1k. For the rear.

 

Is it even possible to run 35s on stock diffs?

 

You will put less stress on your transmission when running larger tires with taller gears. I have 35's and 4.88's and love it. I don't DD my truck cuz I drive my wife's car to work but even on the highway it's not so bad. Your truck with 35's on stock gears, those gears are going to have a harder time turning those large tires thus putting stress on your Trans. Taller gears will help those big tires rotate better. When I had 33's on stock gears my truck was pretty sluggish. I moved up to 35's and 4.88's and gained a lot of low end back. I'm not the fastest guy going down the highway but that's not what I care about haha.

If you decide to go 35's you'll definitely wanna regear. If you order your 3rd from ECGS they will build your diff for you and send it to you. You can then swap it out yourself (pretty easy) and send your core back to them to get some money back. Hope some of this helps

 

If you go to a larger tire, you effectively change your rear axle ratio. The combination of regearing to a higher numerical ratio and the taller tires returns your truck to closer to the original ratio, allowing you to run the same revs and have the same pulling power as in the original condition.

 

If you decide to regear, this will make your choice easier.

http://www.rocky-road.com/calculator.html

 

Interesting. It tells me that 4.10 will be ever so slightly lower geared with my 33s than stock with 30.5 tires. Perfect.

 

When I upgraded to a larger tire size 30" - 32" there was a noticeable drop in fuel efficency. If i regear ill start running 33" maybe 35"
If a taller gear ration reduces stress on the transmision, will it also reduce the loss in fuel efficency?

 

Yes regearing not only brings back lost power but also increases your fuel mileage as you're not lugging the engine

Here's another chart showing optimal gearing for tire size ......

http://www.morris4x4center.com/jeep-tires/tire-gear-ratio-chart.htm?gclid=CKL5vK_Go8wCFU6BfgodkBILZg

 

4.88's would be shorter/lower gears than stock. Shorter gears give you more torque at the wheels. Also helps offset the loss of torque due to having larger tires.

 

^ .. ... this !!!

 

Hell I'm going 4:10s with 265-75-16s. ARB's front and rear.

 

Not completely - you're spinning larger/heavier tires so there is still some fuel cost.

 

If you're rock crawling I would go to a 4.88 gear then get a Marlin Crawler dual case set up with 2.28 geared box and a 4.70 gear box and enjoy crawling slowly !!

 

http://www.grimmjeeper.com/gears.html

 

These gear ratio/tire size RPM calculators are only accurate if you input the actual dynamic tire diameter. You have to measure the radius of the wheel to the ground with the weight of the vehicle on it and multiply that times 2. You'll come up with the true running diameter. It is usually at least a couple inches smaller than the advertised diameter.
This may not seem important, but it makes a considerable difference when selecting a gear ratio.

 

I have heard that before but Im not sure I buy it. A true 33" tire has a circumference of 103.7" whether it is aired down to 5 psi or up to 75 psi. No matter what, every lineal inch of the tire tread touches the road for the wheel to make a complete revolution.

 

No crawling or serious wheeling.
DD that is often used in open fields and rough country roads, some of which wash out regularly.

 

Typically, "Taller" would mean higher gears, ie lower numerical gears in automotive vernacular. Lower gearing (higher numerically) would be what I'm assuming you are after. What THAT would give you is more torque amplification....taking load off engine at a given speed in a given gear...

 

I completely agree. If you DON'T- just look at tire specs (ie Tire Rack or tire manufacturer) for the tire's revolutions per mile. Use 3.1416 to convert revolutions per mile (circumference) to diameter - this is the dynamic tire diameter.
There is a difference between a steel "tire" - ie on a railroad car, and a rubber tire - the weight of the load changes the diameter of rubber tire. Or measure diameter of the tire and wheel before you put it on the vehicle. Then measure when mounted - the tire with vehicle weight on it will have a smaller diameter.

Example Michelin MX2 P245/75-16
Mich spec overall diameter=30.47 inches, rev per mile 683
Divide 5280 by 683 you get a circumference of 7.7306 feet (1 revolution)
Divide 7.7306 by 3.14159 and you get a diameter of 2.4607 feet
Multiply 2.4607 by 12 gives you a diameter of 29.53 inches

As blubuckaroo said, about 2 inches smaller than the advertised diameter.