Gear Hunting - My Solution found by accident

Hello everyone. We are all familiar with the 3rd Gen Tacoma infamous Gear Hunting, you accelerate - or at least you are trying to get moving but instead the engine revs up and ends up in a gear too low to get you going anywhere, until you think you figured it out, either drive with the ECT or get a Re-Program, or just live with it!

Well, here is my report:
2021 Tacoma TRD Sport 4x4 DC SB. 60,000 miles. Drove to Mexico - 1000 miles trip from Utah to Hermosillo. After Flagstaff I experienced a back-fire on level on cruise control at 70 MPH and about 2,500 RPM's. Suddenly the engine went "BANG" in the rear and reved' up to 5,500 RPM until I took it out of cruise control - and I wondered "WHAT THE HEY". Then a minute later, same thing. Then nothing. Got an oil change (was due) in Tucson. Arrived in Hermosillo, took the car in to Morelos Toyota which took me in without an appointment and while there, I thought maybe it's time anyway to get a sparkplug job and the brake fluid compartment was getting low. So I paid them total for the 100,000 KM service and sparkplugs change US $600, and ....

They found the problem that caused the back fire, the harsh REV UP. The Drive Shaft Sensor plug from the engine ECU harness connector was defective and randomly wiggled. Instead of charging me $5,000 US ($2,800 for the harness and the rest labor- which Karl Malone would have done), they fixed the cable - plug terminal that connected to the Drive Shaft Sensor for FREE. I have still the little cables.

The result: At first my truck ECU- system was really confused - it had to be taught new driving habits (mine), and frankly, I discovered within 1 mile of driving, that the stupid REV-UP Gear Hunting illness normally famous in the 3rd GEN Tacoma, has completely disappeared. Problem solved.

I am driving like a brand new Tacoma. I am so psyched, I just did my transfer-front/back diff and transmission fluid service, checked the coolant pH and cool-vs-heat capacities, and flushed the power steering. I tell you my friends in the Tacoma community, it is a real joy to drive that truck without the ECT when I don't need to be on ECT, and without the constant gear hunting.

Disclaimer: I know squat. And this is my experience, and certainly for many, maybe the gear-hunting is chronic and associated to a different problem. But in my case here, I think it is safe to say, my Tacoma came from the factory with a faulty ECU harness, and yes, it bothers me... I drove 60,000 miles with this problem thinking this is normal.

Thanks - and best wishes
TF

 

I bought my Tacoma new and it has never had the gear hunting issue so my harness must be good. What I find strange is your truck never through a code?

 

No, never. And not even after the backfire event. In Mexico, the Toyota dealership was just so good, they said they can't find a code, they just hunted down the possible problems knowing from me what I told them what happened. I think, because the computer needed to learn from scratch, they must have reset the complete master computer, I guess.

I don't know what ultimately was the fix, the repaired harness and solid connection to the Driveshaft sensor unit, or the resetting. Maybe both. Maybe my computer system just worked around the harness issue and as a side effect / symptom was the gear hunting. The Mexicans told me that if the connection is not solid, the transmission can slip or hunt for gears, not shift correctly. The slipping was evident, that was the REV-up from 2,500 RPM to over 5,000 as it backfired, or right after... I really don't know. I heard by surprise the bang and thought some other car next to me on the freeway must have backfired when I heard felt my RPM's up high and looked down onto the Dash and quickly took it out of cruise. The car didn't speed up with the REV-UP... that was the transmission slipping, apparently.


I am wondering what all sorts of problems many of our peers are going through that leads to their version of gear hunting.

 

@TacoFranz - thanks for your insight

 

I have a 22 and I honestly never experienced any “gear hunting” everyone always talks about.

 

Faulty speed sensor connector may have been responsible for the backfire and violent shifting, but the "normal" gear hunting will be back. Try driving more often with adaptive cruise control; that should cause gear hunting to return more quickly.

It was a lot worse prior to the 2020 mid-cycle refresh.

 

My ‘21 had the gear hunting issue right from the start. I damn near got rid of the thing until getting it tuned which makes it liveable but still not great in my opinion.

 

Driving through Flagstaff ( Northern Arizona ) on cruise control?.... wow.... those hills and inclines are brutal
I'd never do such a thing.

As far as this 'hunting' is concerned I've never had an issue with it. I guess I'm glad I don't I have no idea
what the deal is.

 

I am cautious with cruise control. It was level and slightly down hill where I had it on at 70MPH.

 

No violent shifting. It was semi-level with a bit downhill and the cruise control was set at 70MPH and truck was going 70MPH at about 2,500 RPM, a bit lower - it's not like I always look at it (my wife and I were talking so I was paying attention to what she was saying). That's when I was surprised with a bang (metal sound like I drove over some sheet metal), and the rev-up to over 5,000.

gear hunting coming back prognosis? That depresses me. I hope not. I am heading back down to Mexico in end of May. I will take it back to the MEX Toyota dealership for a shock and mount replacement. Drives me nuts, left front shock mount has been clunking ever since I bought the car brand new and of course it never clunks "supposedly" when the mechanics at the dealership drive it, the dip is never aggressive enough for these mechanics. But that said, the Mexicans surprised me very positively. I wonder if they have a solution for the gear hunting - they seemed to be unfamiliar with the problem. My brother in law has the same year same Taco and he has no idea what I am talking about when mentioning the gear hunting. I wonder if this is a US-exclusive bonus, just for us "made in Mexico" LOL, or it's custom-ordered by the dealership "I want 10 TRD Sport Tacoma Trucks WITH GH (gear hunting) feature, and 10 without."

 

Was at the dealership last week for a different issue and I was lucky enough to spend some one on one time with the shop foreman. I printed out and showed him this TSB because it was very relevant to how my truck drove. He didn’t know about it at first but hooked up my truck to the Toyota computer. He said “oh yeah, you’re eligible for this update. Let’s do it.” It took 10 minutes and he didn’t even charge or look up warranty status. It made an immediate difference in transmission shifting and drivability. Not earth shattering, but a significant difference for sure.

My MPG went up by about 1.5 as well.
Check into it

 

This. Much better with a custom tune, but I think there is still room for improvement.

 

This is some great info. Thank you. I read on that report "Delay / Hesitation" and I go "Yea exactly". This is good news. What of course really pisses me off is the fact that "here we are" - You and I, trying to figure this out because the literal majority morons in the dealerships for one or the other reason are idiots on purpose or for genetic reasons. So, if like one other commentator had suggested, the shifting gear hunting and/or delay and hesitation is coming back, I have still the option to get this problem resolved before my Odometer hits 80,000 miles - so about a year and a half from now. And that is also completely unreasonable, people, if you think about it how much money we spend on our Tacos and our willingness to put up with this unreasonable crap. The Toyota concept of Loyalty is just a one-sided one, us being loyal to a shamble.

Thanks. Best Wishes
TF

 

My 2021 Taco Engine / Transmission Codes - Info is 2GR-FKS / AC60F.... Does the "F" make a difference with the Transmission?

 

In the AC60F automatic transmission, the "F" stands for Four-Wheel Drive. The AC60F is a variant of the AC60, specifically designed for use in vehicles with four-wheel drive capability.

 

So, this could imply then that my engine - transmission combination could also be the cause for these reported drivability concerns reported by Sabbathu. For the moment I don't experience lack of power, delay/hesitation, or frequent shift change. After the Morelos Toyota Dealership in Hermosillo fixed the ECM / ECU harness connection to the Driveshaft Sensor, I experience frequent lack of power and so I took the truck back to them a few days after the repair and they adjusted the Idle UP but also told me it will take a little driving for the computer to adjust to the correction (in now receiving correct or better more accurate driveshaft information). And it happened exactly how they said it would. The frequent power lag and hesitation disappeared - the idle-up adjustment was helpful. I am now about 2,500 miles later, and so far it still works all like a champ.

 

Im curious at what rpm is your truck showing on the tach at full temp idling in drive?

 

In 'Park' motor running idle is at 1000 RPM and when putting it into drive - idle without pushing the pedal, the car starts slowly running along on level at 500 - 600 RPM.

 

What was your idle in drive before they raised it? 500 - 600 is normal rpm at idle in gear with foot on brake.

 

I don't know what that was. That low idle happened after they fixed the camshaft sensor connector (I was wrong- it was not the drive shaft sensor). After that sensor connection was repaired on the harness, I experienced random low power and hesitations. That's when I took it back in, and as a 'brief fix' they upped the idle and told me that the power hesitation will go away after the computer has relearned. Everything started going normal. We are back home and after the repair I put on about 2,200 - 2,300 miles; it runs great and shifts smoothly, no hesitations or power shortages. I hope this conversation won't jinx it.