GroversYota

As mentioned above, this truck will be used as a daily driver. But even if it wasn't I'd want the best possible fuel economy the truck could have while still meeting my minimum trail needs. I do spend quite a bit of time in the local woods, but the idea is to take 2-3 trips a year and explore the woods some place else, preferably far away. The more mpg, the further I can afford to go. I do want to learn more technical off road driving skills, but my primary motivation is exploration.

The harsh reality is that gas is only going to get more expensive, and if I take care of the truck it could last me another 200k miles before rebuild, or 10-15 years. Even if I only save 2mpg at build time, the savings will be substantial over the next 200k miles even if the price of gas remains stable over the next decade, which it won't. Build it right, build it once, and have more money left to play.

Thanks much for taking the time to make a real world comparison. That is interesting. I don't have a tack in my truck(yet), but I've been playing with this gear calculator http://www.grimmjeeper.com/gears.html and the numbers you posted don't match what I have from playing with it. Are you sure you have 4.10's? Speedo accurate or corrected? The RPM's the calculator gave for the stock size tire seemed reasonable to me, but I was surprised at the small difference in rpms between 31's and 33's @ 75mph with 5.29's.

The numbers below are rpms taken using the A340H Toyota auto trans(vin sticker says it's what's in my truck) and the default transfer case gearing for toyota. If those numbers aren't accurate for my/our trucks, or I've just missed something, will someone please inform me?

---------------------60mph---75mph
--------(stock)
4.10 & 225/75/15-----2075----2593
4.10 & 31's-----------1893----2366

4.88 & 31's-----------2253----2817
4.88 & 33's-----------2117----2646

5.29 & 31's-----------2443----3053
5.29 & 33's-----------2295----2868


My other Toyota trucks were both taco double cabs, but I realize those are apples compared to my orange. My last long term daily driver before this truck was a 57 Volkswagen bus, so I am more than familiar with the slow lane.
My wifes truck is a 2wd/22re/auto and it's a freakin race car next to mine with the bigger tires.

xcmountain80

I think your on the right track, I remember when I 1st got my gears installed a couple months back the 1st thing I noticed was the higher rpm's. I later realized that even though the rpm's were higher, the truck didn't take near as long to get to speed, it was more responsive (throttle). So I concluded since it got to speed faster and good hold speed easier it wasn't working as hard as it was with the original gear setup. When I 1st purchased my truck some years ago I got 19-20mpg, I added lift + tires and dropped to 16-17.5, I dorve this way for 2 years then geared it and came back to 18 (+/-0.25-0.5). So while initially I didn't understand how higher rpm's could = better mileage and still don't, it does seem to work out.

Aaron

AxleIke

In order to understand the mileage vs RPM's just think about your gas pedal.

If you are in 5th gear, going up a hill, with your foot to the floor, but are at 2k RPM's, you are using WAAAY more gas than if you have your foot only depressing the gas 1/2 way, in 3rd at 3500.

GroversYota

That makes sense to me, all my previous(limited) gearing experience is working with air cooled vw buses, so you put a lot of thougtht into getting up the hills with the power available( as little as 36 hp in some cases!). But on flats the taller 4th ment better mpg cruising on the hwy. The biggest fans of the 5.29/31 set up seem to be in the hills, where most of my hwy miles are relatively flat.

Do the rpms and speeds from the gear calculator above look right to you guys?

xcmountain80

Yes that looks dead on with my 3.4 and auto tranny for the 4.56's but figure with the motor difference it should be dead on.


Aaron

MUDN4R

i have a 4Runner with 33s and 5.29s Auto with a 3.0 i get anywhere between 13-15 mpg. On the interstate if im going 70 its usually around 3 grand rpms whichs seems kinda high but the truck purrs down the road!

tc

Yeah, those numbers look like what I see in Molly's rig.

Note that the powerband starts at 3000 RPM and drops off steeply as the RPM's decrease, so those couple hundred RPM you mention are hugely significant in power (and therefore mileage).

davenjai

I don't know what to say, which is rare. That day my truck was reading 70 mph. I said 75 as I "should" be off by 5 or 6 mph. The 'your speed is this" machine's tend to agree, no GPS. Last night we went somewhere else. It turned a little less rev's, yet still at 2800 plus. it was not the same road or direction. We went north and did a little climbing the first run. I did the wheel turn test to determine the 4:10 gearing. My tires are about done, which makes them more like 30's. I have 33's ready to go as soon as my friend can swap them. I will try to remember to post what it turns once that is done. Mine holds overdrive just fine. I just turned it off to see how it ran for G's sake. I still think our differant elevations has a big role to play.

GroversYota

TC, It wasn't clear in my previous post, but I was pleasantly surprised at the small difference in rpms. I had expected them to be much higer, which screams premature engine wear at me. The smaller difference seems more manageable long term, and I have no doubt I would feel it.

davenjai, the tire wear and a small speedo or tach error could explain the numbers.
The gearing is what it is no matter what the elevation, but I do think the elevation is what makes the difference in holding over drive or not.

At this point I'm leaning torward the 5.29's. My reasoning being that if I don't like it, I can fine tune it with tire size. With 4.88's I get what I get, because nothing smaller than 31's will do.

Thanks for all the input folks

run4her

I am runing a 3.0 auto with 529's and 37, 13.50 R17. I still get anywhear between 13 and 17 mpg. and i live on a mountain in idaho. everywhere u go is uphill or downhill. it isent a race truck but it does ok.

tc

Agreed, that's why I think my recommendations are a bit conservative. If it works up here, it will definitely work down there!

mt_goat

The stock gears would be ok if he had them, but he says he's got 4.10s now. 4.88 would be the stock gearing Toyota put on the 3.0/auto/31" tire combo and even that isn't geared low enough IMHO, especially at higher elevations and towing.

mt_goat

That's right, the 4th gear on the auto is about 0.71:1 that's a higher gear than 5th gear for the manual. It almost like the 5 speed guys having a 6th gear to shift into, ridiculous really for a 150 HP truck to be geared to go 140 miles per hour and it can't even pull 75 miles per hour into a headwind. Now if you drop in a 300 HP engine it's a whole different story.

Here's a good gear calculator for you:
http://www.grimmjeeper.com/gears.html

For example the A340H tranny and 31" tires and 5.29 gears in 4th gear (OD) it shows:
74 miles per hour@ 3000 rpms
80 miles per hour@ 3257 rpms
123 miles per hour@ 5000rpms

BTW I didn't notice any difference in MPG after going to 5.71 gears

liferunner2

I have the 3.0/auto/4.88's and 31" tires in/on my 4runner and when the speedo says 70 I'm at 3k rpm. I'm assuming though that I'm actually going about 75.

Chris

tc

Then you're not in overdrive or the torque converter isn't locked.

mikes19984x4

mtgoat, or anybody else that knows, what transmission and t-case would be in my 98 5-speed with the 3.4l? just wondering, as this calculator thing is pretty cool. thanks.

mt_goat

Really the big variable as I see it is the actual measurement of the tires. Some brands are different sizes than what it says on the side wall and of course wear changes the size. For example, a 33" BFG mud tire has about 1 inch of thread when new, when the tire is at 50% thread it has now become a 32" tire.

Then there is also the speedo gearing variable, IIRC my stock setup of 4.88/31s the speedo was off about 5 miles per hour to the low side. My BMW is off about 5 miles per hour to the fast side. My current 5.29 gearing with 33" tires is almost right on.

Or like TC pointed out the auto torque converter unlocking will raise the rpms too.

xcmountain80

Thats why I buy my tires according to manufactures stated sizing, I learned the hard way after the purchase of Interco SSR in a 285 they measured 33.9" in diameter. Had to overnight wheel spacers,,, yada yada
285 SSR's 33.9"



285 BFG at's d rating 32.8"





Aaron

liferunner2

Tell me more about this. If I start from a stop, I count the trans. shifting four times, which for the auto, would put me at overdrive. How can I tell if the torque converter isn't locking up? It doesn't shift into and out of gear at 70. It maintains that speed quite well, everything feels smooth, and I don't have my foot in the gas very much. Thanks

Chris

tc

If you let off the gas a little, you will see it shift like a 1/2 gear - that's the torque converter locking up. When the torque converter is not locked, you are generating A LOT of heat in the tranny - not good.

http://auto.howstuffworks.com/torque-converter.htm
http://auto.howstuffworks.com/automa...ansmission.htm