vermontoyota

There is a lot of info and opinions on the subject of gear/tire combos and the implications they have on gas mileage.

For my money it seems like anything weaker than stock ratio (ie 33's with 3:73's) would hurt gas mileage unless you're going down a long, flat road.

it seems like anything stronger than stock ratio (ie 31's with 4.56's) would also hurt mileage no matter what you're doing.

It really seems like for typical driving (traffic, hills, acceleration and deceleration, hwy) where you'd really have to work your engine hard to compenasate for a weak gear setup that a stock ratio would provide the best performance and mileage.

I just bought a 1994 4x4 with a 22re and 32" tires. Its got 4.10's and is not too bad until i go up a hill- especially at hwy speed. I live in VT and there are lots of steep grades. i used to have a 1998 reg cab with a 2.7 and 31's and it did quite a bit better (31's weren't stock) until the frame rusted, broke and i salvaged it about 11 months before the "recall"

Anyway, I would like to go to 4.56's (maybe 4.30's because I have a good deal lined up on a set of thirds) and just wanted any feedback on anyone with a similar setup and how it has effected your mileage.

I am correct in that stock ratios will deliver the best all around performance, right?

Junkers88

On a bone stock vehicle this is correct. If you start making changes to tire size or wieght you might want to consider gears also. To explain what I mean I'll tell you what I'm doing. I'm taking my bone stock 86 SR5 (with factory 27 inch tires) and lifting it to fit 33's. The gear ratio calculator that I used to figure my "closest to stock" gearing with taller tires recommended 4.67:1. Since I'll be adding weight (tires, camping gear, extra fuel tank, etc) I decided to go with 4.88:1 to make up for any issues. This is also my daily driver so keeping as close to stock gearing as possible is a primary goal due to rising fuel costs.

Just my couple of pennies.

AxleIke

No.

First of all, 32's are not the stock size. 225/75R15 should be your stock size, but check your door jamb sticker.

That is like a 28" tire.

So that is most of your problem.

I get on average 22 mpg city, 24-26 hwy in my 87 with a 22re, 33's, and 4.88's. I got worse than that with 28's, and 4.10's.

norcalsvx

yea my mpg has improved w/ the 4.88 and the speedo is almost dead on (2-3mph off)

Junkers88

And yet another reason for regearing and larger tires. I'll save money!!!

vermontoyota

"No".....??

I didn't say 32's are stock. obviously they are not as they are not stock on any truck. Changing the tire size changes the EFFECTIVE gear ratio. So 28"'s matched with 4.10's is the rough equivilent to 32's matched with 4:56's. The EFFECTIVE ratio is the same because the reduction in torque from increasing the tire size has been mitigated by the alteration of the ratio.

So like I said, by putting 4.88's on your rig with your 33's you've kept the effective ratio pretty close to stock, maybe a little torquier. and it sounds like i'm correct in that your mileage has not gotten worse (sounds like it even improved).

thanks for the input. i think its a smart mod to do based on what i know and what you're confirming.

Junkers88

Yeah it sounds like we agree, I just didn't state it properly. Have fun!

AxleIke

You are correct here. In your original post, you did not say "effective ratios". You said, "stock ratios" which to the rest of us meant that you were talking about 4.10's. That is the "stock ratio".

Essentially what I read about your post was that re gearing was a waste because stock ratios were better. Obviously I miss interpreted it, but your terminology wasn't clear.

Just FYI, is all, but when talking about gear ratios on these boards, you only refer to the actual ratio of the thing you are talking about.
So, if you are talking about a diff, and you quote the ratio, you do not include the effective ratio of the tranny/xcase/tires, you just say the ratio of the gears you have in the unit. Same with tranny and transfer.

Again, not being a jerk, just easier if we are all on the same page.

vermontoyota

10-4

rereading my first post i see the reason for confusion. ratio=whatever is in the diff.

thanks for the correction, i wasn't trying to be a smartass.

tc

First, 4.56 and 31 IS stock for a manual tranny. 4.88 with 31's is stock for the automatic.

We've got to come up with a better way to communicate/compare gearing for tire sizes. In cycling, they have a measurement called "gear inches" which is essentially how far you go for one pedal revolution:

(the number of teeth on the front chainring / number of teeth on rear cog) * diameter of wheel * pi

The modification for our trucks would be that the ratio is actually inverse, so it would be

diameter of wheel * pi / diff ratio = gear inches

So for 4.56 with 31's = 21.3 inches
4.10 with 28's = 21.4 inches

So, if you wanted to back calculate what gearing you need, you would simply set the gear inches side equal to 21.3 ish and solve:

33 * pi / 21.3 = 4.86

Trustyrusty

Hey I'm planning on getting 33's, and 4.88's would make the gearing almost stock again, so what would I be revving at with 5.29's on the freeway doing 70? I think over gearing might work better for me because I like the skinny pedal!

Matt16

You could find the spacing between gears is short, annoying tops out early.

tc

1 step on the gearing only changes the cruise RPM by 200 or so - it's not like you go from 3000 RPM to redlining it!

If that 200 RPM is the difference between being in the powerband and off, though, it's a profound difference!

jeopardy98

I'm currently running 37's with who knows what kind of gearing. I bought the truck used and it seems to do okay but 5th is currently useless. I'd like to go up to 5.29's and run 35's or 5.71's and run 35's or 36's. Is there a thread on here or a place online that will allow me to see what my speedo error and RPM's at certain speeds in certain gears would be with different gear and tire combinations? Also what do you experts think about my setup? 5.29's or 5.71's. I already know about the arguments for 5.71's being weaker but I'm not really interested in that. I'm just wondering which would be better for me. It is a street truck and it will see some highway use and some towing of motorcycles on a trailer but mostly it will be used to run around town and a little wheeling. I'm also considering throwing a Lock Right locker in the rear when I have it regeared since ZUK said it would be no extra labor charge for that. Might as well do it while I have them out. Sorry for the threadjack...

phildelfino

Very interesting, I never knew this. So 30 x 9.50 x 15 tires are part of my problem, with stock gears all around.

AxleIke

First of all, the "5.71's are weak" argument is complete bull crap. There is ZERO truth to it. It was created by web wheeling idiots with no real idea of how anything works.

Second of all, the 5.71s are a good choice for 37's. You should be able to use 5th without much trouble with those, but not on an uphill.

Third, a locker is a great addition, and if you have to get a lockright, so be it. I hate those stupid things, but lots here have had good luck. Its better than open for the most part, and now is the time to do it, while the diffs are out.

jeopardy98

I agree with you on the 5.71's from my own research. That's why I said what I did. Also, if I plan on running 35's possibly would the 5.71's be too much?

The PO told me that my truck has stock gearing but I don't buy it. The thing wouldn't pull 37's at 70 in 4th at 3000 RPM's would it? Now that is not indicated 70 but that is GPS 70.

TOYOTA 1

i dont realy have a good idea on how there strengths compare technicaly.
but ive seen 5:71's break alot. my buddy runs 38's and hes broken a cupple sets. now hes back to the 4:10's cause we think there stronger. oh and cheaper hehe.

norcalsvx

i have the locker and would'nt do it if you dont wheel that much (are you getting stuck/breaking things?)it's a little diff. than stock for sure

AxleIke

They are the same strength. He's breaking the gear sets because he's running 38's. However, 4.10's ARE cheaper, and so, for something that needs to be replaced, they are a better choice.

Here's a good site:

http://gearinstalls.com/410suck.htm