Not sure 5.29's were the right choice for me, thoughts?

New to the forums here and I'm looking for some advice / perspective. I have a 2020 Tundra that I've been building for the past year. The build currently includes Icon Stage 9 suspension, Nitto Ridge Grappler 35x12.5x17 tires on Method 704's, a Leitner bed rack, full overland skid plates, and sometimes a tent.

When it comes to gears I spent countless hours researching whether to go with 4.88's or 5.29's and probably read every thread in this forum on the subject. The standard advice seemed to be 35 or smaller tires go 4.88, anything larger go 5.29. It seems though that there are a lot of people here that have gone with 5.29's on 35's and love it. I spoke with multiple shops that work on many Tundras, including SDHQ, and spoke with Nitro Gear and Revolution Gear. Long story short, advice was down the middle. Even taking into consideration the extra weight and potential for even more weight in the future if I add a bumper and sliders and driving condition of maybe 70% highway and 30% off-road / dirt-road, about half the people I talked to recommended 4.88's and the other half recommended 5.29's.

Ultimately I went with 5.29's because of the additional weight I was adding. In terms of the driving experience they've been a massive change over stock in my opinion. With stock gears and tires, the truck wouldn't shift in to 6th gear until I hit about 75mph. Now the truck is in 6th gear at 55-60mph, depending on how hard I'm accelerating. RPM's are what you would expect from the typical calculations, at 70MPH the truck is running between 2100 and 2200rpm. The thing that's really driving me crazy, and making me question whether or not I should have gone with 4.88's in my case, is how quickly the truck moves through each gear and the drop in fuel efficiency. With stock gears and tires the truck was getting about 15.5 - 15.8 indicated mpg per tank and now it's getting about 12.8, and that's with mostly highway driving living in rural Texas.

I understand Tundra's don't get the best mileage to start with but that 3mpg loss shaves nearly a 100 miles off my range on a single tank of gas. My intention with the build was to balance being fully capable off-road but also perform well on the highway getting places. I've read about folks getting near stock fuel efficiency with 35's after re-gearing and so I can't help but wonder if I over did it with the 5.29's. My questions for folks here are: Are you running 35's with 5.29's or 4.88's? How much additional weight are you carrying? What's your gas mileage? If you have experience with both, what would I notice different in terms of drivability if I re-re-geared?

It makes me sick thinking about spending that money again but having a truck that doesn't meet my needs might be worse.

TL;DR Not sure 5.29's were the right choice in my situation, thoughts?

 

Did you adjust the PCM calibration for the gears and tire size?

 

Yeah, I forgot to mention I installed a Hypertech so the indicated speed is spot on.

 

35? 5.29 all day

 

Yeah, calibrate for new gears and tire size and you'll see a big improvement.

I think the hypertech speedo calibrator allows changes to gears and tire size.

 

You might also have the transmission control module reset so you can relearn shift points, etc.

Full disclosure: I wouldn't go higher than 4.88 gears with 35s for the reasons you are experiencing. I know a lot of people will claim it's great, but it definitely makes the truck less enjoyable as a daily driver.

 

@dirtydeeds

He will set you at ease. You made the right choice.

 

Also take a long drive to where you know the mileage then compare to what truck thinks you traveled. Then get gas and see what the true number is for mileage.

 

5.29 was the right choice.

if your mpg ‘went down’ something is wrong because that is not what happens

 

They Hypertech does allow adjustments for both but I found that when I adjust for the measured tire size and the new gear ratio, the indicated speed is way off. Right now I just have it set to adjust for tire size and the speedometer is dead on.

Any ideas what could be wrong?

 

So it sounds like you actually haven’t programmed the ECU that your gear ratio is 5.29. The Hypertech does not do it. You’ll need something like an HP Tuner.

 

If I remember correctly, that only corrects the speedometer and odometer. Correcting the actual PCM does not correct the speedometer, but does correct shift points etc..

 

Thanks for suggestion, I'll have to do some research and give that a try. In the mean time, I'm still curious if anyone has a similar set up, 35's and 5.29's, maybe with a corrected PCM, and can actually say they get 15mpg highway.

 

I have 36s and didn't change shit lol idk about you guys switching gears for 35s . Imo it's just the pedal response that sucks and makes it feel like it needs gears. Get a pedal commander and call it a day. Worked great for me, and I just ran moab this weekend lol

 

The Hypertech is usually wrong when you adjust everything right. You have to just eyeball changes to the unit until three speed matches your gps.

The most common variable is a calculation error. After that, the possibilities are needless and I would just be guessing. But somethings off, 100% of the tine, your scenario should gain mpg, not lose it. (When comparing to stock gearing with large tires)

 

My unpopular opinion.

Turn nannies off, drive exclusively in S mode. I get 11.3 - 12.3mpg (GPS indicated). Highway speeds up to 80mph.

<-------- Topper with 300lbs of gear/ tools in bed. Stock gears w/ 37's for nearly 40k miles.

Single passenger, no tow, except for an occasional utility trailer most of the time.

Transmission fluid looks normal after drain and fill.....YMMV

I'd like gears. Hard for me to justify the cost vs benefit though.

Sorry to hear OP. Time for a 46gl Transflo tank?

edit to add: Daily driver/ work truck, country driving/ interstate, no stop and go commuting.

 

I didn't experience any change in mpgs when I went to 5.29s, I'm honestly amazed you ever got 15mpg to begin with. Something sounds wrong with that much drop.

I guess I'm one of those people I daily drive mine 25k a year and 5.29s makes it way more fun to drive. If strongly care about fuel efficiency, and you actually see a decrease with 5.29s then you have a point. I have only good things to say about 5.29s, out of curiosity what made it less enjoyable for you?

 

Something doesn't sound right, my mpg went up after 5.29s, and that's hand calculated, not based off the display.

I have skinny 35s that measure nearly true 35", I daily drive mine and on most days it weights around 6800-6900lbs, before supercharger I would regularly get 15-16mpg after regear, before that it was around 13-14mpg.

 

I didn't regear my Tundra to 5.29s, but drove in someone else's. High revs, limited max speed was my complaint. I felt like both my my Tundras (a 2016 and a 2020) felt and performed better as daily drivers than the one I drove with 5.29s.

I've also read and heard from my local expert that deeper gears have a smaller pinion gear and are more likely to break. Coupling this with my experience driving one I didn't see any reason to go deeper than 4.88s.

 

Limited max speed? Please elaborate.

 

Truck seemed to top out at around 88 mph, if I recall. The owner said that he noticed this as well and that his max speed had decreased somewhat after regearing. Prior to the regear I think he was able to get above 100mph.

 

The truck I drove had 5.29s and true 35's with something like a 3/2 coilover/shackle lift.

 

I see. It sounds like that person also did not update the ECU/PCM that the gear ratio was changed to 5.29s. I experienced something similar until I finally made the update. 100mph+ no problem.

 

A stock truck seems to be governed by rpm more so than the speedometer/wheel speed sensors. If your ecu is flashed then it's not an issue.

 

35s with stock gearing and fully loaded the truck, getting about 13-15mpg. But, I rarely exceed 65mph, when I really need that extra torque, I turn on the tow/haul mode momentarily.

 

An aftermarket tune is gonna make everything better for ya.

 

I knew something was wrong when I tried to pass a vehicle on a 2 lane road and the governor kicked in while I was right next to the car while there was another vehicle coming at me. Scared the shit out of me. Had to slam the brakes to get back behind the car.

 

It is limited by the speed rating on the original tires, there are different stock limits depending on what tires the truck was equipped with though. The 5.29s throw it off and results in the lower top speed. I lost 1-2mpg with 5.29s(this might be due to the 18+ trucks calculating things slightly different), supercharger makes your results not applicable for n/a.

 

My comment is in regards to what is throwing it off. I always assumed the "governor" was based on the speedometer/wheel speed sensors, but that's obviously not the case. The truck seems to reference rpm and governors itself effectively at ~2800rpm in 6th gear, and NOT based off ~108mph. The rpm governor is based off the stock tires and gearing sure, but the fact it's based on rpm in 6th (presumably) is why the top speed is reduced when regeared. I assume 4.88s have the same issue and top out in the high 90s. Easy to bypass that with a tune, since it's an electronic limiter and not a physical hardware limitation.