Issues with 5.29 Gears

Hi all, I’ve been having some issues with the 5.29 gears I had installed in my 2021 Toyota Tacoma and I’m hoping to receive some guidance on what I can do to resolve it. My mechanic who installed the gears says that he has not seen issues like these in the 80+ Tacomas he has worked on and is struggling to resolve them. I’m going to bring it to another mechanic for a second opinion, but I wanted to get your advice first.


1. The truck will not accelerate beyond 88mph. I can feel it electronically cut out the throttle once I get to that point. Prior to installing the gears, I asked the mechanic if this would be an issue since I read online that some people experience it. He told me this was an issue that only happened with Chevrolet trucks.


2. The gas mileage has fallen considerably since installing the gears. This is especially frustrating since improved gas mileage was the main reason I wanted the gears. I often drive from San Diego up to Mammoth Lakes (roughly 400 miles) and used to get 19-20 miles per gallon. This has dropped to 15-16 mpg since the gear swap. For regular around-town driving, it has dropped from roughly 15.5 to around 14.


3. The truck is shifting in odd places. When I’m starting from a stop downhill, the truck starts to roll when I press the gas but doesn’t seem to engage the gear until I’m going around 5mph. When I am braking while going downhill, it often downshifts and causes the RPMs to spike to around 4k until I come to a near complete stop or put it in neutral.


If anyone has any advice on how to approach this next, I would love to hear it! Thanks!


Truck Specs:

2021 Toyota Tacoma TRD OFF ROAD 4WD Long Bed

Falken Wildpeak A/T3W 285/70R17

Method 701 17x8.5” 6x5.5”

Icon Stage 3 Lift Kit

Hypertech Speedometer Calibrator

 

For the speed limiter, it was about 108mph stock. For whatever reason, the speed limiter is sensed by the AT output shaft speed. Now that you have 5.29s, the limiter is blocking you at a lower speed. A tune can easily take care of that, as well as the shifting issues.

 

1. Is a common known issue, your mechanic doesn't know what he's talking about.

2. I don't buy that you got 19-20mpg driving up a mountain with 285s.

The transmission has no idea you changed the gears.

 

You got 19-20 mpg going 80+ on stock gears and 285s?

 

Actually everything sounds right about normal.

 

as all the others have said - your experience is normal. You will need a Tune to fix the speed limit issue and shifting issue - the mileage will improve with time but not appreciably. Gears do not increase mpg - they decrease mpg and increase torque. More RPM = lower mpg. DM @tonered or @mZiggy and they can set you up with a Tune to fix the fixable. Totally worth the investment.

 

1. Known issue, what's happening to you is normal.

2. How are you calculating fuel mileage? Can't use the truck's calculations displayed on the dash. Fill up, measure distance (odometer corrected by tire size), and divide by how much gas you pump back in. But you shouldn't expect fuel economy to increase with lower gears.

 

Also retune expectations while you’re at it.

 

Nobody said that though.

 

Normal results with the gear swap.

 

why do you need to go above 88 mph? anyways, all these issues are normal when you change the gearing. the ECU doesn't know it has a different gear ratio. You need a tune to make everything work properly.

 

I wanna know, what crystal ball you were looking into, and thought you would get better mileage, top speed, and better shifting? You changed the whole dynamics of how the truck was designed/engineered.

 

You win today.

 

Can I win twice?

 

Well, only one winner per day. Unless you mod that BTTF Toyota Pickup with a Flux Capacitor?

 

These people might get mad at me if I tried. </thread hijack>

 

Bruh did you read the OP?

.....
"I often drive from San Diego up to Mammoth Lakes (roughly 400 miles) and used to get 19-20 miles per gallon."
.....
"Falken Wildpeak A/T3W 285/70R17"
.....

OP didn't explicitly say 19-20mpg at 80mph, but it's reasonable to assume he was since he's complaining about not being able to go over 88mph. Also guessing he's in Cali, where grannies are driving 80+

 

Hahaha! Sweet Pickup!

We wouldn't need to see the Flux Capacitor, but Mr Fusion might be a bit obvious.

 

I remember thinking I had a huge mpg drop on an old truck when I changed from 32s to 33s.
But it turned out it was just a change of season. Cold air, wind, etc have by far the biggest impact.

Having said that, did you not think that going like 90ish mph with 5.29s would be good for mpg?
The only thing lower gears do to lower mpg is to increase rpm, and there's a little compression loss turning the engine.