just tourque, the engine has to spin faster to turn the wheels.

 

so does it affect mpg?

 

Well yes, unless you just start driving slower to compensate.

 

Re-gearing will improve mileage and relative power when using 35" tires compared to the original 32" tires. Right now, you are losing power as it dissipates in the drivetrain, as the larger diameter tires take longer to get started, and rotate less at the same speed. This causes the engine to "lug" - running at a lower rpm than designed for a given speed. You lose power to the wheels, and use more fuel... Regearing gets the engine turning in the correct rpm range for most efficient power output, which in turn improves fuel mileage....(not to mention proper operation of the ABS system, tranmission shift points, etc...) :bigthumb:

 

I am putting the icon 3 in lift and not much bigger tires... should i change my gears?? i dont even know what size tires i should put on when i lift it... HELP PLEASE!! thanks guys!

 

Gear ratio changes are used to compensate for larger tires, so you won't need to regear even with the new suspension...

Tire size recommended is 285/70R17 or 305/65R17....

 

that makes sence, thanks for correcting.

 

Save your $$$ if you're not doing any off highway driving.

Freeway driving your RPM's will be lower and if you do decide to regear DON'T go with 4:88's go with the 4:57's! When I run my 35's (BFG KM2's) the 4:88's are just too short still for the freeways, but I'm impressed when I run the 33's which are BFG A/T I can get up to 15mpg if I stay off the throttle.

You'll do better with mpg with the stock gears and just downshift when your climbing hills or need to pass someone.

these are 20" rims with BFG A/T which measure out to 33"

and these are 16" rims with BFG KM2 385/16 which measure out to 35"

good luck...

 

Weird math Vic? You should have lower revs running 35s with 4.88 gears then 33s with 4.88. Also, I think you mean 305/16, not 385... Sorry had to pick on ya .

 

GOOD CALL TONY! I'm a knucklhead :mecry: not think'n right...my brian's frozen...it's cold here in Big Bear.

THX, V

 

Like what larry said, when i regeared i rarely see downshifting on the highway and hence get better mileage.

 

Well, its going to be a while before I can save upthe money to get new gears. Do you think I will be ok for a while just running the stock gears?? I will just take it easy on the throttle like some of you said.....

 

I agree with Larry and will also say that you can certainly "live" with it on-road. Like he said, its a matter of efficiency...

 

On average whats the cost to regear both front and rear diffs?

-B

 

$1100 and change for both gear sets and both master install kits and shipping, plus labor to install.

 

Where is the best place to get the gear and master kits?

 

Depends on what ratio you want. Nitro Gears from JTs parts & accessories Toyota : JTs Parts & Accessories, Justdifferentials.com are the only people making 4.56 gears on wide bases that fit the stock carriers. Yukon makes good gears, lots of people buy their 4.88 gears. Toyota is the only one I know of that makes 4.11 gears for the front diff.

Just make sure to get U.S.-made gears (except Toyota). Yukon and Nitro are both U.S. made.

 

Thanks for the info. I am still deciding between 4.56 and 4.88. I have a MT and am moving up to LT305/70R17/E Nitto Terra Grapplers. I haul a raft trailer (~2,500) lbs nearly every weekend from Apr - Sept. Also, I live in Colorado at high elevation and it feels bogged down as it is towing. Recommendations?

 

I'm running 285/75/17 Toyo MT tires (71 lbs. each!) on a heavy auto tranny FJC and I'm happy with 4.56 gears, even in the mountains, but if I was towing a trailer in the mountains I would seriously consider the 4.88 gears. Actually, I don't think there would be a question in my mind, I would definitely go with 4.88 but that's just me.

 

Thank you. That is what I am thinking. I would rather be on the safe side. I am also considering a Lefty Inchworm as a mod for this Spring.

 

I am also considering a Lefty Inchworm as a mod for this Spring.

Lefty is a great mod, and will open up a whole new world of control and capability for you.

 

1911. How do you think your vehicle would respond with 4.10's instead of the 4.56's? Thanks!

Zane

 

I considered 4.10 (4.11?) gears, but decided against them for two reasons:

1) They're only 10% lower gearing than stock. Using this nifty on-line calculator: 4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators I was able to see exactly what rpm I would be turning for any speed with my size of tires, and I didn't think that 10% lower was enough for 34" tires and the weight of my truck.

2) The only 4.10 gears I could find for the front diff were Toyota, and let me tell you they are proud of them! 1.5-2x the cost of quality aftermarket gears.

Having said that, Jim D here on the forum runs 4.10 gears with 33" tires and likes them I believe. Using the calculator I gave the link to above will let you play with and accurately see the effects of any diff gear, tire size, and transfer case combo.

 

regearing is well worth the money.....on 33" tires you can get by with 4.11 to get back to stock ratio or close to it....4.56 to give you a little extra umph off line and offroad.....IMO 4.88 are too much unless 90% offroad vehicle or tires are 37 or larger.

it helps get the rotational mass of tire moving with less effort so can save fuel and keep engine from lugging at lower speeds as was mentioned above...going too much on the gearing though will make rpms too high at highway speeds and also cause excessive use of fuel as mine drops considerably over 2200 RPMs.

I would say 4.56 max for your setup....4.11 if you want to get it close to stock feel. I am staying 33" tires and will be regearing next year unless something breaks before then. JT has the gears that do not require new housing..... or can use to put an ARB up front as well.

I think it is a good choice for anyone with oversized tires...onroad or offroad.

 

I created a quick chart that compares some gearing/tire options for MT. It is not all inclusive by any means...but rather just some info that I put together in making my decision for gearing/inchworm/tire size. I calculated these numbers...so if you see any errors, just tell me. You are going to have to maximize the images.
:cheers:

 

With all due respect to your work there, an easy to read chart is available at the same site 1911 and I have been using and referring to. Take a look at this link, it may be easier to read and compare different tire sizes and gear ratios...
4Lo.com :: Gear Ratio & Tire Size Chart

 

Thanks for the reply! Definitely a nifty chart. Too bad no one makes a 4.27 or a 4.30 gear for our rigs. Might make for a nice compromise between the 4.11 and the 4.56.

Zane

 

edit: errp... never mind.