Re-Gear ? 1fz-fe sweet spot for MPG? (1 Viewer)

[7schulz]

No it will go off road, I'm thinking 4.88 will be good and I will just have to drive a tad slower, like 60mph, that would put me at 2200 rpm when I have to drive it to work.

 

[alia176]

4.88 will force your hand with 315s IMHO and for your elevation, you'll be annoyed with the slight over revving of the engine. Unless you have a mighty heavy 80. Again, this is purely subjective so take it for what its worth. Driving around in the Midwest, I think having long legs is nicer than having high torque. Now, when you come out to the West for a vacation, having 4.88s + 315 is very nice.

 

[7schulz]

There is only 39 RPM difference between 4.56 and 33's and 4.88's and 35'
There is only 12RPM differenc ebetween 4.56 and 35's and 4.1(stock) and 31's
So what are you saying would be the best set up?

 

[d0ubledown]

Take a look see what you think.

[snip]

i think you're overthinking this with all these numbers. they really dont mean squat. dont forget, with bigger tires, unless your speedo is corrected, it will show a slower speed than what you're actually travelling. so if you're revving at 2200 and your needle says 65mph, you will most likely be going 70+ish mph.

just take the formula for figuring out what gears you want. its really simple

new (or desired) tire dia / stock tire dia X current axle ratio = new ratio

for example:

315s vs stock 275s:

( 34.6 / 31.15) X 4.10 = 4.554

therefore 4.56s will put you back into the stock powerband, where 4.88s will leave you at slightly higher revs..but in a 'sweeter spot' for bigger/heavier tires which is what 315s are and why most go to 4.88s

as mentioned earlier, you'll get better hwy mileage with bigger tires and stock gears, but worse in stop & go traffic. its a trade off, and theres absolutely no point in trying to mod an FZJ80 for better fuel economy, because its never going to happen, especially when bigger tires are in the picture. if you want optimum fuel economy, add lighter weight, and drive like a granny.

...or get a different car to commute to & from work.

 

[Hilux]

x2 on everything doubledown has said (get a damn Accord or Camry already. You've got the money for a regear... and not a $1-$2k dependable beater? you can drive an old cruiser, but not anything else? )


And I'm gonna throw another wrench in the works...

Tires are not exact to what size they say they are...

Ok, so it's a 1/2" (or more) off at brand new tread... Wonder how many rotations a tire can rack up in a hour? Or mile? Miles... per... Hour?

Here's A BFG... BFGoodrich Tires | All-Terrain T/A® KO | Tire Sizes & Specs

And here's A Super Swamper SSR | Interco Tire


I'm not looking up every tire manufacturer... I just happen to have been looking at those the past few days...

add lighter weight,

 

[7schulz]

I had a civic but hated driving it so I got the LS400(see sig) to drive. My hand is forced with the regear, the front is shot and to buy 4.10's again would cost the same as 4.88's or 4.56's so I was checking out my options. I was just using tirerack's measurements for the goodyear wrangler dura trac and the 315's come in at 602 revs per mile, and the 285/75/16's are at 634 revs per mile. So I am at least using consistant data.

 

[IdahoDoug]

Seeking better fuel economy with gearing changes isn't going to pay off. You're overthinking this and making unwarranted assumptions in the process. RPM changes (usually lowered) don't de facto make for lower fuel consumption in a gasoline engine. If you got lucky (pure chance without actual fuel flow/load research) then the actual real world difference might be a few measly percentage points.

The main determinants of fuel consumption are elsewhere. Things like vehicle weight, aerodynamics, size and shape of vehicle, vehicle speed, elevation and driving habits. You could spend $2000 on regearing and I could change my driving habits alone (free) and achieve better fuel economy gains. Or I could remove my roof rack (free), the 3rd row seats (free) and put in a fresh air filter ($24) and double your economy gains.

Simply physics is your battle. At 65mph it takes X amount of horsepower to overcome drag and propel a 5500lb vehicle down the road. To generate X amount of horsepower it takes Y amount of fuel burn. Do it at a different RPM and it still takes that same amount of fuel burn.

So, don't go chasing gear changes for fuel economy and expect a payback. Rather than doing all that calculation around an ASSUMED benefit of fuel economy, simply calculate the cost of regearing and then solve the number for the amount of fuel you'd have to save over perhaps a 3 year period. If it turns out you'd have to reduce fuel burn by 10% just to break even then you know it's not going to pay off. I know it won't pay off, but I'm just saying attack this problem from the simply direction of investment vs payoff and you'll get a picture more quickly.

 

[7schulz]

I HAVE TO BUY NEW GEARS NO WAY AROUND IT. SEE PREVIOUS POSTS. So it is not a cost comparison between re-gearing and fuel economy. I have asked for the fuel and torque curve and I haven't been able to come up with one yet. This thread is about optimizing those curves with gears and tires. NOT DRIVING HABITS. To which I also said I drive like grandpa, I also removed rear seat and tow hitch and moved the spare tire to the back. Both of which were for ground clearance not weight but they do reduce weight too, double bonus. I’m not worried about final MPG b.c weight and height will be added down the road.
I am trying to optimize efficiency (the torque and fuel curve) of the 1fz-fe.
So I could really use a fuel curve if anyone has that info.

 

[IdahoDoug]

PS - explain more about the "gear tooth" you found in the front diff (a pic would be best), cause unless its yowling or otherwise I think you saw something different come out of the diffy.....

 

[IdahoDoug]

There's no such thing as the data you're looking for. The fuel curve/torque curve hinges on load. So at a certain RPM the engine burns X fuel at load A. Or Y fuel at load B, Z fuel at load C and so on. Your engine is constantly changing RPM at the same load also - when the torque converter unlocks, when it changes ratios then finally shifts down, etc. If you were doing this for a "stationary" engine such as that powering a generator you would be closer to having that data but what you're looking for is a continuum, not points on a graph. And it's not going to exist anywhere outside an automotive testing lab with fuel flow monitoring and variable loading dynos, etc.

This is a great discussion, but a difficult goal.

 

[7schulz]

I'm almost 100% sure it was a gear tooth. Nothing else is up there, and it had machining marks like a gear would. I lost the piece during clean up. The front diff has a whine @ 20+mph all the way up 80 and probably plus. It only goes away when you left off the gas/ no torque on the drive line. The steering also binds up in parking lot turns. It will skip/chirp a tire.(probably what caused the broken tooth. Probably from a seized VC in the t-case.) I am having Out Back Off Road Gear, Greenwood, IN. look at it in 2 weeks so I would like to know what gear set up to go with before. And b.c it is such a big chunk of money I don't want to be unhappy with it, which is why I am going over kill on the numbers.

Wouldn't someone that has added a turbo or sc have gotten a pre and post fuel curve data?

Even under a nominal load, like stock configuration, there should be a fuel curve for acceleration and maybe one for curising, or a combination there of.

 

[7schulz]

These are all Diesels but they all have a sweet spot for fuel consumption and this helps in choosing the right axle ratio
Cummins ISB / n/r 2000-2400

ISC / n/r 1900-2100 w/ 2200 gov
2000-2300 w/ 2400 gov

ISL n/r 1600-1900 on highway

ISM n/r 1500-1700 on highway

ISX Up to 85k / 85-140k GCW
<1750 1400-1600 / 1500-1700
>1750 > 65 mph cruise 1370-1450 / 1500-1700
>1750 < 65 mph cruise 1400-1600 / 1500-1700


DDC MBE 926 <= 210 1950 - 2100
>= 230 1900 - 2050

MBE4000 n/r 1400 - 1500

Series 60 n/r 1400 - 1500

DD13 n/r 1400 - 1500

DD15 1375 - 1475


Mack 2007 MP7 11L NA 1450-1550 rpm
2007 MP8 13L NA 1400-1500 rpm
2010 MP7 11L NA 1400-1500 rpm
2010 MP8 13L NA 1350-1450 rpm


Volvo 2007 D11 11L NA 1300-1500 rpm
2007 D13 13L NA 1300-1500 rpm
2010 D11 11L NA 1400-1450 rpm
2010 D13 13L NA 1350-1450 rpm

International Truck Governed Speed
MaxxForce 7 2800 RPM 1850 - 2100
Maxxforce DT 2600 RPM 1750 - 2050
2400 RPM 1700 - 2050
MaxxForce 9
MaxxForce 10
MaxxForce 11 2100 RPM 1600 - 1750
MaxxForce 13 2100 RPM 1375 - 1500

 

[Hilux]

I HAVE TO BUY NEW GEARS NO WAY AROUND IT.

No you don't.... Finding somebody parting one out will save you at least @ $200...

B/c that's labor you don't have to pay a man to rebuild the gears of your diff... And are you gonna take the pumpkins out? That's prolly another $100.

So far you're up to $300 in labor ALONE... ballpark...

Not only that, but if you're locked, YOUR diff still has value... Just not as much. You just have to find a guy wanting to regear and upgrade to E lockers at the same time. (not hard AT ALL Mini guys are looking for them to)

So minus a $100.

You're now at $200. Buy an already geared factory diff at +/- $200, and swap them out yourself... And you're breaking even on the labor ALONE.


God I hate being poor... It makes posts like yours sound conceited.


You're fixing to spend 2,000 EASY, and in a futile attempt to save some MPG. How much gas can $2,000 buy?... And option #1 you just spent $200... Really, $0.00 compared to paying another guy labor to fix it.


[Killer Beaz] SAVE UP!!![/Killer Beaz] The Apocalypse is coming!

 

[7schulz]

I'm not just gearing, I am having the birfs and inner seals done too b.c all of my fluids are mixing( moly and diff) and I am going to help so I can learn what's going on in there. It could also be the axle shafts where the tooth came from so I need experience on what’s going on in there. And while they are in there I might as well gear up if needed. They do have a locked front axle in there shop collecting dust. But if i do want to get at least 33's and maybe 35's I should re-gear.

 

[Devil's Slide Doug]

If had access to a cheap complete stock third member and I lived in the flatlands and I was only going to run 33s then I would not bother changing diff gear ratios.
If you are absolutely going to mount 35's then I believe the consensus is to use 4.88s. The 4.56s just seem like an intermediate step that I would not waste my money on.

 

[7schulz]

That was my origional plan stock gears 3 inch lift and 33's. But if I do have to do something. It might be smarter to pay the labor to regear than to pay for a whole axle and labor to instal it.

 

[Hilux]

I'm pretty sure I busted my ring gear(found busted tooth in my diff oil) by having the VC in my t-case locked up, well the PO did anyway.

ehhh... not necessarily... You might have bigger fish to fry...

Read this: Toyota gear install

" Tommy purchased this sweet 1996 FZJ80 from New Mexico and while driving it home on the freeway started to get a loud rumble from the front end. The viscous coupler in the transfer case was believed to be mal-functioning and tried to lock up....the result was tremendous resistance as felt by the ring and pinion contact and tremendous heat. The pinion has no place to dissipate heat and probably got close to cherry red. The ring gear is a larger surface area and was able to dissipate the heat to the case and the oil thus less damage to the ring gear."



It's official... I hate viscous couplers... IH8VC's

Do yourself a favor and remove it and add a CDL switch... Damn Toyota marketing division...

 

[Devil's Slide Doug]

Unless you have 35's already, it is not smarter. You already have to dig into the front end no matter what so that is a moot point. My guess is the used third member might be cheaper than purchasing gears and having them installed in both the third members. with stock gears you don't have to touch the rear end which will save you money.
A few years down the road when it is finally time to change gears because you go up in tire size you can yank the third members your self and have someone set up the gears and then you reinstall the diffs. At that point you need to do the work yourself because if you really need 315's+ for the sort of terrain you are wheeling then you also need to know how to fix your junk if you break it on that gnarly trail that requires that size tire.

 

[azTony]

I will be driving 4.88's and 315's this time next week

 

[cruiserruf]

i don't know, but if i was concerned about gas mileage than i would have gotten a honda civic. i'm not really concerned about gas mileage when i start adding things like 35" tires, bumpers, R&P, extra weight like cargo drawers and fridges, etc.

if you have to fill up every 50 miles now that's a different story