Thanks Brian894x4, I have quite a bit of noise coming from my rear now I guess when I can't take it anymore I'll put the 4.56 gears in when rebuilding.
4.56 ratios = better economy
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Help needed after reading this thread - I am upgrading to a 33" tire, what is the best gearing for my 94 DD.
No need to regear. Get your tires and drive for a while, if you feel the need to regear at that point, then, you can figure out if you want to be close to stock or go a little further.
Ok here is some more use less info for those that do not know...
1st: If you change the stock tires hight ANY it directly affects the stock gear ratio, you no longer have the "factory" gear ratio along with the factory recommened tire hight.
instead you have just successfully changed, for the worse, your gear ratio (yes you did) by changing the hight of the tire, you mathmaticly change the final drive.
The factory intended for the vehical to run in it parameters thats why you got the gears you got, an engineer that makes a whole lot more $ than you do applied mechanical advantage to the trannsmission and D.T, with the vehicals weight and some other factors involved, oh...mabie like how much towing capacity they want it to have vs. fuel consumtion.
The mechanical advantage he applied is better known as the motor or engine and that motor is what has the parameters that dictated the engineres decisions on what parts (gears) to use.
2nd: that mechanical advantage has peaks, curves, and specifications it must fill becouse an enginere that makes a whole lot more $ than you made it.
the long of it is, it has to provide a specified power output probably based on the weight of the engine (& or life span). to do that it must turn an amount of RPM's in order to have an output, and those RPM's are in direct relation to the engineres choice of capabilitys and specifications of that particular vehical.
If you alter the tire size by hight you are basicly deducting that in gear ratio and changing every thing the factory based it's specifications for.
The factory also do NOT factor in someone's personal prefrence.
3rd: Now that motor that was desighned to go down the highway, 70 MPH @ 3,000 RPM's (the engines most eficient RPM or "peak") is now runing, becouse you changed the tire/gear, 65 MPH (although the speedo says 70) @ 2,800 RPM's NOT the engines most eficient RPM or "peak".
the motor is contantly beeing lugged around.
those figures are not exact that is off the top of my head to make it exact I need a calculator and your final drive ratio un corrected.
Further more for the benifit of other readers "gas" and "Diesels" are two compleatly different motors and there for different rules apply in there build specifications.
Gas: (1,500- 5,500 rpm) lighter weight, Typicly generates more popwer in the mid to higher RPM.
like the voume on a sterio the more you turn it up the more power it genorates.
Has a vacume and that vacume is highly sensitive to changes the engine overcomes the loss of vac. with fuel.
Diesel: (idle- @2,800 rpm) useualy heavier, genorates a massive amount of power at very low RPM's. Has NO vacume fuel is pumped in by a very high pressure.
Not as sensitive but will not genorate mid to high RPM's.
like the opposite of the volume of a sterio the more you turn it up the more it decreases in power
1st: If you change the stock tires hight ANY it directly affects the stock gear ratio, you no longer have the "factory" gear ratio along with the factory recommened tire hight.
instead you have just successfully changed, for the worse, your gear ratio (yes you did) by changing the hight of the tire, you mathmaticly change the final drive.
The factory intended for the vehical to run in it parameters thats why you got the gears you got, an engineer that makes a whole lot more $ than you do applied mechanical advantage to the trannsmission and D.T, with the vehicals weight and some other factors involved, oh...mabie like how much towing capacity they want it to have vs. fuel consumtion.
The mechanical advantage he applied is better known as the motor or engine and that motor is what has the parameters that dictated the engineres decisions on what parts (gears) to use.
2nd: that mechanical advantage has peaks, curves, and specifications it must fill becouse an enginere that makes a whole lot more $ than you made it.
the long of it is, it has to provide a specified power output probably based on the weight of the engine (& or life span). to do that it must turn an amount of RPM's in order to have an output, and those RPM's are in direct relation to the engineres choice of capabilitys and specifications of that particular vehical.
If you alter the tire size by hight you are basicly deducting that in gear ratio and changing every thing the factory based it's specifications for.
The factory also do NOT factor in someone's personal prefrence.
3rd: Now that motor that was desighned to go down the highway, 70 MPH @ 3,000 RPM's (the engines most eficient RPM or "peak") is now runing, becouse you changed the tire/gear, 65 MPH (although the speedo says 70) @ 2,800 RPM's NOT the engines most eficient RPM or "peak".
the motor is contantly beeing lugged around.
those figures are not exact that is off the top of my head to make it exact I need a calculator and your final drive ratio un corrected.
Further more for the benifit of other readers "gas" and "Diesels" are two compleatly different motors and there for different rules apply in there build specifications.
Gas: (1,500- 5,500 rpm) lighter weight, Typicly generates more popwer in the mid to higher RPM.
like the voume on a sterio the more you turn it up the more power it genorates.
Has a vacume and that vacume is highly sensitive to changes the engine overcomes the loss of vac. with fuel.
Diesel: (idle- @2,800 rpm) useualy heavier, genorates a massive amount of power at very low RPM's. Has NO vacume fuel is pumped in by a very high pressure.
Not as sensitive but will not genorate mid to high RPM's.
like the opposite of the volume of a sterio the more you turn it up the more it decreases in power
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I used to be Worldwide Powertrain Planner for General Motors in Detroit, and routinely designed and evaluated MPG testing. Prior to that, I was Product Planner for GM's North American Luxury and Sporty vehicles. I don't often bring this up, but did since this subject (I just increased my MPG) is so fraught with emotion and subjective opinion I thought it worth heading off the inevitable disagreements by folks who're sure they're correct despite having a test sample of 1. Sorry that sounds heavy handed.
Anyhow, barring a repeal of the laws of physics, there's no way you're going to improve MPG by installing shorter gears. Fuel consumption is highly related to RPM and if you turn the engine over an extra 100 times/mile you're using more fuel. Theorizing that the engine is working less hard because it's pushing less hard at a higher RPM is incorrect. Over that same mile with that same vehicle at that same speed, the engine did the exact same amount of work. Work translates into the burning of fuel. However, you added another 100 revolutions, which increased the fuel burn. How? Many ways, but the easiest to explain is that those 100 extra revolutions took whatever amount of power it takes to overcome your engine's friction to accomplish.
There's no free lunch. If you put on bigger tires than stock, then compensate with gearing to get back to the same RPMs you will NOT end up getting better MPG than the vehicle did stock. No way. Why? Many reasons, but the easiest is that you added heavier tires and the vehicle must overcome that rotating mass which takes power.
I've read many claims that people regeared after installing bigger tires and now they're getting better MPG than stock. 'Taint so. There's enormous error in measuring your MPG and making such a declaration due to changing conditions from temps, to altitude, fuel quality, blah blah - as many variables as you can think of. We did digital instrumented testing under rigorous testing protocals on a daily basis and I cannot ever recall shorter gearing improving MPG. Was there a certain precise MPH/RPM that this happens? Yes, but it was a narrow band and since there were losses at every other MPH/RPM the overall effect was a loss of MPG. Possibility of a freak occurrance that all that testing did not reflect an 80's particular characteristics and this improvement could in fact take place? Let's call it 50,000:1 against just to leave a sporting chance.
If you're putting larger tires on than stock, you've just increased the fuel consumption of the vehicle and decreased its acceleration and deceleration times vs stock. Want to get back the acceleration (can't get back the decel) by regearing? It's a fine idea but accept that you're going to further deteriorate the vehicle's MPG.
Sorry to be so blunt, but this is a science outcome. Because our actions affected GM's CAFE and market share, we agonized over every gearing decision and every tire size decision. To give you an idea of the impact, while working on the Cadillac Allante we found that increasing a single tire size reduced the MPG on the EPA's urban loop by around 3/4MPG. That was only a tire SIZE, not moving from one type of tire to another as most of you are doing in moving from the stock Michelin P metric to a much less MPG friendly mud terrain or all terrain tire. Doing that might have increased the MPG loss by 50%.
Most of us (myself included) don't really care much about the MPG as we've decided to drive around in a vehicle that can go anywhere offroad at the price of being ridiculously inefficient onroad. But take heart in something AlGore would be proud of. I will guarantee that your decision to purchase a used 80 makes the "carbon footprint" of your transportation decision FAR smaller than a brand new state of the art Japanese hybrid such as the Toyota Prius Hybrid, or Honda Accord Hybrid. Probably less than half, in fact. So put an "I'm green" sticker on your lifted 80 and proudly smirk at these misguided buyers, knowing that if they blew a red light in front of you while late for a Greenpeace fundraiser you'd crush them like a bug and reduce the US's transportation carbon footprint for the better.....
DougM
Anyhow, barring a repeal of the laws of physics, there's no way you're going to improve MPG by installing shorter gears. Fuel consumption is highly related to RPM and if you turn the engine over an extra 100 times/mile you're using more fuel. Theorizing that the engine is working less hard because it's pushing less hard at a higher RPM is incorrect. Over that same mile with that same vehicle at that same speed, the engine did the exact same amount of work. Work translates into the burning of fuel. However, you added another 100 revolutions, which increased the fuel burn. How? Many ways, but the easiest to explain is that those 100 extra revolutions took whatever amount of power it takes to overcome your engine's friction to accomplish.
There's no free lunch. If you put on bigger tires than stock, then compensate with gearing to get back to the same RPMs you will NOT end up getting better MPG than the vehicle did stock. No way. Why? Many reasons, but the easiest is that you added heavier tires and the vehicle must overcome that rotating mass which takes power.
I've read many claims that people regeared after installing bigger tires and now they're getting better MPG than stock. 'Taint so. There's enormous error in measuring your MPG and making such a declaration due to changing conditions from temps, to altitude, fuel quality, blah blah - as many variables as you can think of. We did digital instrumented testing under rigorous testing protocals on a daily basis and I cannot ever recall shorter gearing improving MPG. Was there a certain precise MPH/RPM that this happens? Yes, but it was a narrow band and since there were losses at every other MPH/RPM the overall effect was a loss of MPG. Possibility of a freak occurrance that all that testing did not reflect an 80's particular characteristics and this improvement could in fact take place? Let's call it 50,000:1 against just to leave a sporting chance.
If you're putting larger tires on than stock, you've just increased the fuel consumption of the vehicle and decreased its acceleration and deceleration times vs stock. Want to get back the acceleration (can't get back the decel) by regearing? It's a fine idea but accept that you're going to further deteriorate the vehicle's MPG.
Sorry to be so blunt, but this is a science outcome. Because our actions affected GM's CAFE and market share, we agonized over every gearing decision and every tire size decision. To give you an idea of the impact, while working on the Cadillac Allante we found that increasing a single tire size reduced the MPG on the EPA's urban loop by around 3/4MPG. That was only a tire SIZE, not moving from one type of tire to another as most of you are doing in moving from the stock Michelin P metric to a much less MPG friendly mud terrain or all terrain tire. Doing that might have increased the MPG loss by 50%.
Most of us (myself included) don't really care much about the MPG as we've decided to drive around in a vehicle that can go anywhere offroad at the price of being ridiculously inefficient onroad. But take heart in something AlGore would be proud of. I will guarantee that your decision to purchase a used 80 makes the "carbon footprint" of your transportation decision FAR smaller than a brand new state of the art Japanese hybrid such as the Toyota Prius Hybrid, or Honda Accord Hybrid. Probably less than half, in fact. So put an "I'm green" sticker on your lifted 80 and proudly smirk at these misguided buyers, knowing that if they blew a red light in front of you while late for a Greenpeace fundraiser you'd crush them like a bug and reduce the US's transportation carbon footprint for the better.....
DougM
powderpig
SILVER Star
As always the MPG stuff is fun to read. Thanks Doug for the laugh at the end. Later Robbie
The only question with that theory is that by contrast we should "always" get better gas mileage with high gearing then? I could be wrong, but I doubt that an LC would get better mileage with 3.42s.
I think for that theory to be correct, we have to assume that the factory gearing is 100% the most efficient set up that Toyota could have come up with for that particular rig, weight, tire size, engine and tranny. My point is that I question whether that's the case. I know it's been suggested that I'm foolish to question a Toyota engineer's expertise, but I can point to several gear/tire ratio mistakes that Toyota made and then corrected in later model years. So, they are not infallable. The decision to retain the same 4.56 gearing with autos and manuals on the mini/4Runner when 31s were added was a mistake that Toyota corrected in the final years by adding 4.88s on auto rigs to compensate for the auto's high over drive (which is the same high overdrive as the Land Cruiser).
There also may be other reasons Toyota feared going with a lower ratio in the Land Cruiser, such as 4.30 or 4.56 and that may be that they felt the lower gearing and the resulting tooth mesh might be less reliable over the long term and Toyota's primary design concept, was extreme reliability, even over power and fuel economy.
At the time, the 1FZ was Toyota's largest and torquiest engine, but more importantly, the Land Cruiser was by far, it's heaviest vehicle, so it's not unreasonable to think that Toyota engineers may have feared going with a potentially weaker gear ratio than 4.11.
Also, if Toyota was that concerned about achieving the absolute best fuel econony, they would have redesigned the tranny and rear diff gearing, but instead...they use off the shelf parts, despite completely redesigning the LC80 and then later redesigning the motor to the 1FZ. Instead of picking a perfect ratio for the overdrive and diffs and cutting brand new years, the engineers only had a few options to select from. That being 3.90, 4.10, 4.30, 4.56 ratios for the diffs and .70ish for the overdrive. The engineers selected 4.10s...by the way, the same ratio used with the 3FE, which is a completely different motor, with completely different power curve. So that doesn't necessarily mean it was the best gearing.
We can also talk about Toyota's auto tranny gearing differences compared to the manuals and how that affects final drive rpm by as much as 20% or around 500 rpm and why lower gears in auto tranny rigs were considered necessary by Toyota on every 4x4...except, strangely....the Land Cruiser. Since Toyota used 4.10 gear both on manual and auto models, obviously one model or the other is incorrectly geared, since the manual will run on the highway at much higher rpms than the auto.
By the way, I'm not suggesting that a lower ratio than 31/4.11s absolutely would definately bring better gas mileage. I don't claim to be an expert by any means. Just questioning the conventional thinking here based on my mini-truck experience. It sounds like you guys have had this discussion many times before. Despite being here for 3 years, I've only recently checked the board daily. If all my points have already been brought up and debunked then my appologies for bringing up old arguments.
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Agree that Toyota had a wide variety of design goals with the LC and also agree that optimal MPG was waaaaay down the list. But will still hold to the point that starting with ratio X from the factory, moving to a taller ratio will generally yield MPG increases/performance decreases and moving to a lower ratio (as is discussed here) will do the opposite.
Also, remember that this discussion assumes that the larger tires are part and parcel of the regear decison being debated. Getting back the MPG lost to larger tires isn't happening.
I think what you allude to is "could there be a better MPG gearing on the totally stock 80 that Toyota could have chosen?" and the answer is almost unequivocally "Yes" because the LC was not optimized for MPG. But I'll guarantee it's in the higher gear ratios than stock, not the lower gear ratios.
DougM
Also, remember that this discussion assumes that the larger tires are part and parcel of the regear decison being debated. Getting back the MPG lost to larger tires isn't happening.
I think what you allude to is "could there be a better MPG gearing on the totally stock 80 that Toyota could have chosen?" and the answer is almost unequivocally "Yes" because the LC was not optimized for MPG. But I'll guarantee it's in the higher gear ratios than stock, not the lower gear ratios.
DougM
Don't make me get my calculator!
So Doug..................
will an Fj80 6" slee'd, ARB'd, 37" mtr's with NO gear mods yeald a better fuel consumtion than..............
an Fj80 6" slee'd, ARB'd, 37" mtr's with 5:29 gears?
What's the difference in stock tire stock gear vs. 4:88's and 33's
4:88's w/ 32's
4:88's w/ 35's
5:29's w/ 35's
etc etc
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I don't mean to elude that going to a lower ratio with a taller tire will improve gas mileage over stock. In my mini-truck experience, I've never seen a truck with taller than stock tires, even geared correctly, get better than stock mileage. But I have seen mileage dramatically improve over what it was with taller tires and stock gears.
If your theory that higher gears should improve LC mileage, then would it not stand to reason that 33s and 4.11 gears would yield a mileage increase over stock, assuming the LC is otherwise stock weight and height? The weight difference between a 31" tire and 33" tire is nominal assuming they have similar tread width and the affect on the final drive would be like going from 4.11s to 3.86s.
I still have questions about the engine using more fuel at higher rpms regardless of other conditions. Again, I am no expert here and I’m just simply talking this out trying to understand it. I think your theory makes perfect sense on an engine that has no load. But I think, once you add a load, things totally change. I don’t believe an engine makes the same h.p. at all rpms under all conditions and therefore does not use the same amount fuel at all rpms under all conditions.
For example, sitting with the tranny in park, and revving the engine up to 4000 rpm is not putting out the same h.p. or using the same amount of fuel as if the engine were on the highway pushing 70 mph, pulling a trailer at 4000 rpm. If that’s true, then engine rpm isn’t the sole determiner of fuel consumption.
With that in mind, I believe there is a difference in fuel consumption and how hard an engine is working, depending on it’s load. I believe an engine can work harder and use more fuel at a lower rpm, depending on the load. But, but maintaining the same load, yet increasing engine rpm, by raising the gearing (with tranny or diff gear selection) could decrease the load on the engine as the engine begins to operate in a more efficient rpm range. Less throttle is used and therefore, less fuel. That’s my theory. Of course, it’s all dependent on the engine, it’s power curve, the vehicle’s weight, tires, and tranny and diff gearing.
I’m not suggesting by any means that higher rpm under a given load always equals less fuel consumed. I think it entirely depends on the engine and other factors.
Sorry, I honestly don't mean to be argumentative.
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Most people are going from stock ~31" all season type tires to a 33" (or larger) A/T or MT tire which are generally quite a bit heavier. Unsprung weight, like a tire or wheel, has a much more significant impact to things such as mpg, than the weight alone would lead you to believe.
EDIT: unsprung weight probably isn't the right term, can't think of it right now.
EDIT #2: duh, rotating mass is what I meant...
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Alright guys, IYHO I'm running stock gears and I want to go to a 33" tire. What would be the best gear ratio for overall performance for my ride? Remember I said overall performance.
Gas?
Diesel?
driving conditons? i/e, DD every day highway/ payvment/ low speed driving?
driving style?
I know you say 4.5 but I think theres a diesel 4.5 aswell, dont know.
this is easy calculate the rpm's with 33's then get as close to stock as possable with the avalible gears. (you remamber how it felt w/ stock tyres right?)
they wont be exact so....
With the two ratios +/- your needs or prefrences.
Diesel?
driving conditons? i/e, DD every day highway/ payvment/ low speed driving?
driving style?
I know you say 4.5 but I think theres a diesel 4.5 aswell, dont know.
this is easy calculate the rpm's with 33's then get as close to stock as possable with the avalible gears. (you remamber how it felt w/ stock tyres right?)
they wont be exact so....
With the two ratios +/- your needs or prefrences.
Gas w/automatic, all driving around town and highway.
What are my options?
98% mini guy here just bought an 80.
I'd say 4:56's, with engine enhancements (towing, offroading, minimum) for better milage. (keeps the O.D low but still in the curve, if it's not enough go to 32's it's only a half inch difference)
4:88's if you do any towing or offroading. (your O.D will be a little short/ "Low" the distence bettween cruising rpm and red line)
I will add a gear page, so people can see and blue print there desisions, you need a calculator, the trannies gear ratios, the available gear set ratio's, and the tire sise you plan to run.
Further more these are my opinions. What you deside is not my responsabulity
you asked me I'm tellin you If you aint happy forget trashing me and sell the setup diffs to some one that knows what they want, and go back to what you know.
98% mini guy here just bought an 80.
I'd say 4:56's, with engine enhancements (towing, offroading, minimum) for better milage. (keeps the O.D low but still in the curve, if it's not enough go to 32's it's only a half inch difference)
4:88's if you do any towing or offroading. (your O.D will be a little short/ "Low" the distence bettween cruising rpm and red line)
I will add a gear page, so people can see and blue print there desisions, you need a calculator, the trannies gear ratios, the available gear set ratio's, and the tire sise you plan to run.
Further more these are my opinions. What you deside is not my responsabulity
you asked me I'm tellin you If you aint happy forget trashing me and sell the setup diffs to some one that knows what they want, and go back to what you know.
gears
4.3 can be had for 80 series. I have a complete rear locker 3rd member w/ a matching front r&p.
4.3 can be had for 80 series. I have a complete rear locker 3rd member w/ a matching front r&p.
right on.but the mpg is not drastic.i would not waste my time with 456, go with 488
How much of a mpg difference are we talking about?
