Ok, my Ranger has 3.45 gears with a 7.5 rear end. I was wondering what gears would be food for a 31 inch tire. I'm thinking 3.73's or 4.10's. Also, anyone know a place to get a rear locker? And how much will it effect mpg? Thanks, and I'm wanting a good deal thats not too expensive!

 

4.10s

 

4.10's are perfect for ya

 

How much will those run me installed? Also mpg?

 

we need to atleast know what size tire is on there now, what engine, transmission, and roughly what mpg you are getting too...no magic ball for mpg. Every truck, everyboy, and every combo is gonna be different.

 

I have 27's on there with a 3.0 engine, not sure about transmission, all i know is it's a 7.5 and it gets 17 city/21 highway.

 

well getting them installed by someone will always be expensive.

 

6.17s

 

omg those would kill gas mileage!.....wait do those kinds of gears even exist for our axles?

 

Here's the equasion for ratio equivilency....

New tire diameter / stock tire diameter x original gear ratio = equivilent new ratio needed.


For Example.....my truck....

34.8 / 30.5 = 1.14 x 4.10 = 4.67

Now...since there's no 4.67 ratio avaliable, and 4.56 and 4.88 closest to it. I choose 4.88, for slightly lower than stock final gearing.


General rule:

higher number = higher rpms at fwy speeds, better in city mpg, lower fwy mpg, "feels faster".
lower number = lower rpms at fwy speeds, not too good in city mpg, higher fwy mpg, "feels slow".

^^those are kinda exaggerated...but you get the picture...i hope.

 

4.56's or 4.88's are going to KILL!!!! your mileage. Thats pretty over kill for you. I have a 3.0L, 5 speed, 4.10's and 31's. It has plenty of grunt to get up and move. Now I've had 3.73's and it did fine did great on the highway as long as there were no hills. 5th gear was for cruising plan and simple. I couldn't pass anyone in it just had to down shift to 4th and it would go (slow but it would move). Now going up to NH from CT I had to shift to 4th a lot of the time and even 3rd if it was a big hill and I was hauling something.

I'd go with 4.10's. I love them and sometimes I think they could be overkill. BUt its the best option IMO.

 

Do I get this done at a local auto shop or are they easy to install? I have no idea as I'm not near a mechanic lol. Also I should get about 15-16 city mpg with 4.10's and 31's right?

 

You'll have to get someone to install them. You have to set the backlash and shim them just right or risk screwing up a lot of stuff. What you can do is go find a 8.8 out of a Ranger with 4.10s. You can install that with just basic hand tools in a afternoon. You should be able to get the axle for under 300 bucks too.

 

Dang that sounds pretty good lol, I'll look into that, and also has anyone locked there rear?

 

lol

 

fxwannabe was using his truck as an example with the 4.56 and 4.88, he was not suggesting this for kawaboy.

 

are you 4x4 or 4x2? if your 4x4 your gona have to change the gears up front too just letting you know.. im assuming 4X2 since you have a 7.5 and 3.45's.. sounds like a base model :)

 

4x2

 

4.10 is what the original poster needs, imo. either 3.73 or 4.10....all depends on whats powering those tires. Food lucking finding a 7.5" locker. Just get an 8.8 with the correct gear ratio already. If you're not that mechanicly inclinded, you should steer away from installing your own gears.

What your trying to do in the gear change, is move that torque curve so its usable again. That equasion i posted shows what ratio to go with to make the final drive ratio the same as stock, meaning same torque curve. basically ditching the need to down**** or lugg you engine, using more fuel than that of a stock ratio + bigger tires. believe me, having an mpg on the fly gauge helps....and having a manual really sucks, ESPICIALLY WHEELIN' IN 4Low SUCKS! with 4.10 and 35's.






I was merely posting what a gear change is, what a possible solution is, etc.

 

yes, with 31s you will want to go with 4.10s, and the easiest and cheapest way for you to do that is to go to a junk yard and get a ranger rear axle (either 7.5 or 8.8, they are both more than strong enough for 31s and a 3.0) and bolt the entire axle into your truck. From your picture it looks like you have a gen1 or 2 truck, and 4.10s are tough to find in the older axles, however you can use the 93-08 axle in your truck, it will just be about 1.5" wider than the old axle. 4.10s became a really common ratio after about 2000 or so and it is very easy to find one of the newer axles with that ratio.

 

i do believe you can get 6.17s for the 8.8, dont quote me on that though, its something stupid low beyond reason.

 

Imagine, a doubler and 6.17's in the axles., with and a low 1st gear. oh the awesome crawl ratio.

 

add a 4bt up front.. that would put some insane torque down.. may want to think about something besides a stock ranger frame lol

 

I have a 2007 fx4 with 4.0sohc, 5spd auto, I believe it's 8.8 with 4.10 running on 31s from the factory. I believe I get around 15-16 and I would very much enjoy a little better fuel economy. Here's a photo of the little beast lol