So, i've done some searching here at yotatech, and found the regear formula to be as such: ((diameter of New tire)/(Diameter of stock tire))*(Stock gear ratio in differentials). This makes sense to me, but i wanted to clarify with some gearheads out there.

So, my 87 4runner has stock tires, and stock gear ratio, which i found the code for on the plate on the firewall under the hood. The tires i have are about 28.5 inches in diameter (they're metric, and so i just took out a tape and measured as best as i could). I would like to go to 33's, and i have 4.10:1 in the diffs. So, my math looks like this: (33/28.5)*4.10= 4.74.

So, my questions are: Is my math correct? If i go to 4.88:1 (seems to be a common size), how much will my gas mileage drop? I live in colorado, and i run 85 octane fuel, and i am currently getting 22-23 mpg.

THanks for your help.

Axleike

 

Not sure about the gas mileage, but you can double check your gear ratio math here

 

Math looks right. Your mileage will stay about the same with the new gears and tires. With the added lift and heavier/wider tires you will have added drag and this will likely shave a little off the mileage. Actually, if you go to 5.29s, you may get better mileage than with 4.88s. I know I did with my '85, I had better MPG with 5.29/33 than with 4.88/33 combo. But I prefer the 4.88s on the highway, lower revs and more comfortable on long drives.

 

I have 33's and 4.88's with a thorley header and flowmaster exhasust through a freeflow cat and 2.25" piping. I also run the K&N FIPK.

One time I got 22, babying it on the freeway, But I haven't been able to get that again.

I caonsistently get between 18 and 19.

What can I do to improve this. I try to take it easy on the engine, but maybe I am not revving high enough. Ideas???? 22-23 sounds awesome

 

yup, math looks good to me
wow you can run 85? everytime i put 85 in my truck it pings. i guess i should clean the carbon out of my engine. anyway, back to your question: within reason, the gearing shouldn't affect milage very much. it may be [harder/easier] to turn [shoter/taller] gears but you'll go [more/less] distance per revolution so it all averages out in the end. the only thing you really need to concern yourself with is that you want to keep the engine revs at it's most efficient, which is probably what you are at when driving 55mph with everything stock. you'll probably notice some hit in milage with the extra energy that larger tires absorb and the larger cross section you'll be punching in the air due to any lift you'll be adding to fit those tires.

here's a data point for you: i switched from the stock 28's to 31's in my '89 without regearing and i get identical milage (about 20-22). also make sure that when you calculate your milage with the new tires and gears you'll need to adjust the miles driven because the odometer will be off a bit.

 

I had 33s and 4:88s on my 85 (bone stock 22re) and got 19-20 real world and 21-22 on highway trips - exactly the same as when stock. She liked to rev - on long trips the faster I drove the better the mileage got. Best ever was 24mpg two tanks in a row on a 500 mile round trip over the mountains at night both ways pushing it hard. Go figure.

 

man i must be retarded b/c im still confused. i have a 99 3.4L and i just recently added 33's on top of a 2.5 lift. i used to get like 19 city. and now i get like 14. what ratio should i do to boost me back up there?

 

See the formula in the first post above. You didn't say what gears you have but here's how it works. (PLug in YOUR current gears to get your new ratio) If you had 225s and 4.10s then 33 / 28 * 4.10 = 4.832 so you want 4.88s. If you had 31s and 4.56s the math is 33/31*4.56= 4.854 so you'd want 4:88s! If in the middle between 2 ratios you usually would want the higher number (lower gears) to help make up for the extra drag and mechanical losses of the bigger tires.

 

Sorry I've been away so long, just back up on the internet.

DeathRunner: I'm not sure what else you can do. I have a very similar set up as far as intake and exaust, (it's downey, but it's still 2.5 inch pipe, and the air filter is probably alsmost identical) Could just be the engine. My old one (the one that got 22-23) had 245,000 on it, but the oil was changed every 2500 to 3000 miles, and the plugs every 6-12 months since it had 9000 miles on it (that's when my pops bought it back in 89.) My new engine (just a new 22re) is only getting 19-20, but it is still winter up here, so we'll see when the weather get's warmer.

Mike D: I'm not sure about that man. the truck has never had anything but 85 in it, and it never pings. I noticed that you are in boulder also, what color is your truck?

Thanks all for your responses. I'm not really doing the gear swap for the gas mileage so much as for the power. I don't need to go fast, but i do a lot of mountain driving, and i need to be able to do at least 55 up the hills, since that is the speed limit. Thanks again.

 

maybe the carbed motors get better mileage than our EFI's that's about what I'm getting with my 89 motor.

 

possibly, but my first motor was efi too, in fact my new one is using the same efi that my old was. Did your intake use a new connection hose going from the MAS to the EFI unit? Mine is about .5 inch bigger than stock, so that might make a difference, but i don't know if it is enough to increase by 2-3 MPG by itself. I was thinking it might be emissions stuff, but my truck was bought in CA too, and it has all the CA emissions hardware, as i'm sure your's does. I'll have to think about it some more. Are you using all TOYOTA parts in your engine, ie plugs, wires, etc....? I also run 10W-40 oil, and 80-90 in the tranny. I have a 5spd manual as well. Not sure how much of a difference this all makes, but maybe some of it.

 

Where did you get this new piping between the MAF and EFI??? Mine is stock. I just have the K&N FIPK.

I am using NGK plugs and Nology plug wires (They have a capcitor and send more juice) I use 10w-30 and 80-90 in the tranny. Been thinking about switching to synthetic in the transfer, tranny and axles.

I'm running 33x10.50's with 4.88s....so my tries do increase drag a little.


Let me know if you can think of any differences. -Seth

 

the new piping came with my downey intake setup. it's a crome piece that was to replace the old plastic hose that runs across the engine. It's a bit bigger. (i had to really trim away alot of the rubber on the attachment hoses at the ends of the pipe to get it to fit.) The 33's with the 4.88 is exactly what i want to get, but i am still running the 4.10's with 235 75's because of money issues ( the new engine after the timing chain on the orignal slipped a notch and casued problems). I am running all toyota everything on the ignition and firing setup, and it sounds like yours is better anyway.
I only have about 1.5-2 inches over stock lift in the front, and 2.5 in the rear. It looks as if you are running a long travel set up, so maybe the drag is the difference.

Other than that, i've found that when i take it easy, and don't race out of a light, and i drive in the proper gear, ie shift down before the engine starts comlaining about being too reved or too low, then i get better mileage. If i'm constantly stomping on the accelerator, then it is worse.

 

I try to take it easy on the pedal. I learned that wether I mash the pedal or ease it....my 22re still accelerates the same. so I try to only get into it about a 1/2 inch or so. I think I under rev it because the header is so loud. I think it sounds higher to me than it is. I have a gauge cluster with a tach, I'll see when I put that in.

 

I realistically get between 14-16 on the interstate going 70 too with my 4.88/33 combo.

If I hit 85 (on the gauge so really ~90 or so) the rpms are winding so high that I don't feel like I'm doing the engine any favors so I rarely venture above 70 (on the gauge so really ~75).

 

I didn't know that you could hook up a cluster with a tach to the hookups from one without. How do you manage that?

 

I haven't done it yet, but Protrux (Toyota guys) gave me the unit and set it would be all good except for the oil pressure gauge.....you need to tap into something. Anyway I think the tach is electronic. I'll post when I get around to it. My big thing is changing the miles on the new one it is about 20,000 less.

 

Oh yeah....so even with the 33/4.88 combo our speedo is off????? Maybe I'm actually getting better mileage. I thought that was supposed to correct everything and bring it back to 4.11

 

you have to take the difference between starting and ending mileage and add 1/10 of that to the difference itself. like 225 miles on the tank, you add 22.5 miles to 225 to get 247.5 miles on that tank. in my runner it's off exactly 1/10 of a mile per mile. so when the gauge says I went 1 mile, I've really only gone 1.1 miles.

IK believe the gauge would be closer with 4.56 gears and 33's.

The reason you go to 4.88's or even 5.29's is for more torque, not to correct the speedometer or better the gas mileage.