The 5.29 Mega Thread!!

this is one of those things where, yea, technically it might be an issue… in reality this just isn’t a thing. People do break gears, but they’re doing things that 99.9% aren’t going to do with OEM axles, stock frames, etc.

 

R&P don’t break because of tooth size, they break because of abuse.

 

What many fail to understand is that tooth size or count is mostly irrelevant. Sure, the teeth are larger on 3.91. Why does it not matter? Leverage. a 5.29 gearset is "easier" to turn, due to the lower ratio which generates higher mechanical advantage. This means for the engine to turn the pinion, is easier than the engine turning the 3.91 pinion. What this means is that the teeth are seeing much less force. Sure, they may be smaller on 5.29, but they are experiencing 35% less stress, so unless their strength is reduced by more than 35%, it's a wash.

A good example is a bicycle. The front sprocket is the pinion, the rear sprocket is the ring gear. The lower the teeth up front, and higher the tooth count out back, equals the easiest way to pedal. Use the large sprocket up front and the small one out back and you have to practically stand on the pedals and yank the handlebar to get the pedals to move. The first scenario is 5.29, the second scenario is 3.91, and the sprocket teeth on the 3.91 setup are experiencing extreme forces while the first setup does not.

It's all leverage. Another way to look at it is that companies sell the gears, they warranty them, and they don't put gigantic horsepower/torque or tire size limitation disclaimers on the box. If they were that fragile, they wouldn't exist or they would have huge disclaimers.

The final proof is tacomaworld, as stated I have never seen a failure here. If there was one, it would be well known. Even if there was 5% failure rate, you could chalk that up to improper install.

 

Ok, been on the 5.29’s for almost 800 miles. Got my flush done today. As of now, I’m seeing +\- 4mpg increase over stock on fallen wildpeaks 285/75-17.

no gear hunting. Smooth, linear excelleration. Stays in 6th almost all the time. Can excelrate nicely in 6, pass in 5th. Barely ever sees 4th on the highway.

shout out to Stellar Built in Sacramento. Full service install, included all lubricants, 500 mile flush, inspection and refill. 2 day turnaround and great service as always.


taken today.

 

I’m getting regeared to 5.29’s tomorrow. I have 295/70/17’s, skid, sliders, roof rack, bed rack, and RTT. Will probably add bumper and winch at some point. Automatic transmission. I drive about 1.5 hours on the interstate each day. I’m getting about 13 mpg average and the truck is running in 4th gear much of the drive because of all the rolling hills in north Georgia. I was back and forth on the gear ratio but because of the weight I carry and hilly terrain I live in, I think I made the right decision.

 

How is this possible? 4 mpg? So you were getting 13 mpg on stock gearing from the computer? There’s literally no way you’re seeing that increase. Your tests are clearly not very comparable.

i regeared and the transmission still hunts but being in Colorado everything is a hill. Did you also get a tune? How about cruise control, is it still a gear hunting devil? Mine still is terrible.

I’ve put 1,500 miles on mine so far and certainly doesn’t seem to be a magic pill some of you chalk it up to be. Happy I did it but some of y’all blow the benefits way out of proportion

 

Several posts have come up about millage in the mountains. It's always worse for you guys. In the 2-4 mpg better range seems average after the re-gear/tune. Thats about where I am if I stay in the 60's on the highway. As I get over 70 closer to 80 it falls hard. I'm in Florida so its all flat. There have also been some posts about using a lighter gear oil helping with the mpg. I'm running the ECGS recommended heavy lube, so no experience with the lighter oil. If you have not tuned yet I recommend it. After the tune you will notice the trans holds the gears longer so there is a ton less shifting and the truck will feel lighter on its toes. Similar to the first couple of times you drove after the re-gear. Its been a while for me so I'm used to it now. Once you are able to drive it for a while in a flat area closer to sea level you will really be able to feel the difference. Depending on where you spend most of the time driving you're dealing with inclines and thinner air, both are mpg killers. It really makes a huge difference where you drive, which is why some people will see/feel a large change and others will see a minimal effect.

 

Best mod you will make with your heavy beast. At least that’s the way I felt. Have Rich tune your truck as well, it also adds to the goodness. @Stormpeacock

 

100% get it tuned. Probably the single greatest mod I've done to this truck

 

Thinner air doesn’t kill mpg at all. It kills hp. I was getting EPA rated mpg stock a mile above sea level. Driving up to 9,000ft+ still got 21 mpg round trip (2 mpg due to inclines). I suspect these mpg numbers nobody is doing a real test with the same loop in the same temperature. Most of what mpg change is being seen is convoluted variables and people justifying their expensive purchase. Most people who have taken data show slight decreases with new gears and after breakin it’s close to a wash maybe slightly better or worse. This is true across a host of vehicles not just 3rd gen tacos.

sure I can slow down to get better mpg. Has more to do with air resistance than engine power band. Mpg has most to do with load on the motor. Hence why I get basically the same mpg before and after, within a few tenths. This post mentioned nothing about a tune where maybe you could squeeze 1ish mpg out. But to claim mpg increases 4 mpg would imply Toyota could get better mpg by regearing the truck. They would’ve done that a long time ago if that was the case. Going to 5.29s on 33s definitely is lower geared than factory which will reduce mpg because let’s face it factory gearing was chosen to squeeze mpg out

 

Speaking of MPG I'm currently on 33s but will be going up in size on my next set of tires (probably a year or so). Around town I'm getting 12-13 at best and on the freeway if I keep it at no higher than 70 I'm getting 15.5. When driving to Montana this summer from San Diego with a loaded down truck and 3 guys we averaged 14. We also were cruising at 75. It didn't hunt as badly but the hit to MPG was pretty significant.

 

I think this is just a misunderstanding: nobody is saying that regearing improves mileage over stock, just that it can help regain some of the mileage lost by oversizing the tires and overweighting the vehicle. This is why the argument that "if it's so much better Toyota would just do it" isn't relevant because the truck doesn't come from the factory with 300 pounds of extra weight or 33" tires. It comes geared for the curb weight and configuration that it's intended to run with. If they did come from the factory like that there's nothing to say that Toyota wouldn't ship them with 5.29's.

 

Keep in mind that Toyota doesn’t really gear it for MPG. Well, in a way they do, by their theoretical mpg calculation that goes into their CAFE rating. But that is not real world.

The main factor with gearing, though, is the ability to claim lower emissions. Gearing it tall to run low rpm means low emissions, plain and simple. They’d probably do the same to the manual trans but the performance would suffer too much for people needing to shift their own gears.

Toyota does not give a crap what your real world mileage is. They care about apppeasing to the EPA, which means focusing on their CAFE average which is calculated, and focusing on emissions. If your mpg sucks in the real world, it isn’t their problem, it’s yours. That’s not to say low gearing always helps mpg either, but the engine has a spot where it wants to rev to make the most efficient use of its power. There are many situations where that doesn’t end up being where the factory geared a vehicle to run.

 

Thinner air kills HP, lack of HP means you press the gas pedal further which increases rpms to make it up and then since you are pressing the gas pedal more you will use more gas. So, yes thinner air is a millage killer. We could argue with exact details of all the steps in place, but really all that matters is the end result - Less MPG.

You are correct in terms of the numbers. I highly doubt most people are setting up a science experiment in the cab to accurately measure gas consumption to a 10th of a gallon. Most of the data provided is what the on board or aftermarket apps read out.

Also remember most people re-gear after adding larger tires which will have an effect on MPG, so any increase in mpg is just an attempt to get closer to stock.

Also, assuming what Toyota should have done long ago makes no sense when you don't understand all the factors at play.

It reads like you are having a hard time justifying your large purchase. Nothing is a magic pill, everything will have its limitations. You should go test drive a stock Tacoma on the same roads you take now or find a friend with a Tacoma and switch driving so you could get his/hers impression of your Tacoma. The difference between the two might be enough for you to feel good about your purchase. Sometimes it's not about the actual data/numbers but how much more enjoyable the driving is. It sucks you feel like it wasn't worth it, I hope that feeling goes away with time.

 

I should have taken a pic before the the regear, but I was always hovering in the mid 14mpg to low 15mpg. So overall, its 3-4 mpg better. When I take my drive up to and back from sacramento, it tops out around 18.5-19 mpg with the constant cruise control function set somewhere between 65-70. I do have a KD Max tune, but have not had it retuned yet for the gears, tires and cai. I run mid grade all the time, but have the option to run the shit 87 here in california a the tune will adjust overtime for the octane change. All in all, the reger should pay for itself in gas in about 18mos.

Its was steep price, no doubt, but even with the non-updated KD Max tune, there is 0 gear hunting, even when I use the adaptive cruise, which puts the truck into the OEM tune. it stays in 6th most of the time, and can easily pull up a hill in 5th now. I love it, this is how the truck should have driven from the start.

just found this pic from about a week before I had the regear.



This was from the drive home the very first night. Of course this was the break in period, I was keeping it most at 55mph. And the I confirmed with a GPS tracker, my speedo off by -3. So 52mph = 55mph.

 

Gearing has nothing to do with emissions. Have you ever had your emissions tested?

This isn’t the 1980s with carburetor engines. Computers are able to adjust fuel/air mix from 0 feet up to usually 12,000 feet….

People in Florida have the same HP and MPG as those in Utah.

Altitude is often oversimplified as mountain driving and in those cases it’s not “altitude” that kills mpg it’s the changing grades and if the road such as steep ascents and hill climbs.

 

The more rpm you turn, the more emissions you put out. Gearing it tall to keep the revs down will slow down emissions. Manufacturers will absolutely make that performance sacrifice with the gearing on your behalf in order to lower the emissions their vehicles make.

That said, if like the Tacoma, 6th gear is really tall in stock form, and it ends up spending lots of time in 4th and 5th to make up for it, then it may be a wash. But still, low rpm = lower emissions, so the more time it spends at low rpm, the better it is for Toyota‘s ratings.

Besides annual state inspections on my 94 before it reached 24 years old (sniffer in the tailpipe test), no I haven’t. Hard to do that going down the road with various gearing at different rpm levels. That’s the only way you’d know, or on a dyno. But, on the old tests, they’d do it at idle and do it at 2000 rpm. Obviously the rpm level matters.

 

That horsepower comment isn’t true. You lose HP in fuel injected cars as well. Forced induction not so much if at all.

As you said fuel injected car will compensate and keep the a/f ratios, etc the same where as a carbureted will have issues in a drastic elevation change. But HP will definitely de affected.

There is just simply less air to play with which leads to less HP.

 

You actually get better MPGs at higher elevations. Less air, less fuel. Also staying under 50MPH is helpful. Things get extra turbulent at higher speeds. So many variables. I actually got great fuel economy thru the Rockies last year. Still in stock gears though.

 

Hit the nail on the head. Less oxygen the computer throttles back gas. Maybe you get better gas mileage in flat, but I’d still argue it’s the thinner air mostly not the engine being more efficient.

When you're climbing a hill, converting gas energy to potential energy, if you assume the motor is lossless it’s super simple math. If you assume there’s losses, the motor will generally be the same efficiency no matter what. Regearing won’t change much at all. What many are missing you're talking about efficiency. Doesn’t change when you add or remove weight from the vehicle. All that kills your mpg same with bigger tires because you need more energy to move the weight not that the motor is less efficient. If anything the motor will be more efficient with more weight, but still you’d get lower mpg. A car is very inefficient at freeway speeds purely due to the minimal amount of power needed to keep moving. All of this comes down to load. Load is very basic energy calculations. Gas burning releases energy which converts potential energy to kinetic energy. Changing gearing doesn’t change that fact which is basic physics. All efficiency changes will be very minimal unless you talk about a specific speed but nobody drives at 1 speed only in the real world due to hills, traffic, weather, speed limits, etc. Rpm’s has almost nothing to do with mpg. There’s threads on that if you’re so inclined. I haven’t found a chart for Tacomas but on other cars there’s charts that show it can be marginally better at a specific rpm but when your load changes (like going up a hill) it’s a different rpm that’s most efficient (usually it’s higher). The computers will keep you there and your efficiency won’t change much at all. Toyota even describes this in the brochure which creates the unpredictable behavior most people complain about

i got 21 mpg stock and on 35s I get about 17. Before and after gearing there was no change because my truck still is being driven the same speeds, same terrain, etc