Looking for advice on 3rd gen shift problems (not the normal complaints)

I'm having issues with the shifting in my 2019 AT off-road and am in search of some advice.

I'm familiar with the normal 3rd gen AT issues, and what I'm experiencing is not any of those.

The truck has had progressively more difficulty shifting over the past couple months. When the truck chooses to shift is fine (or at least behaves like a 3rd gen). However, I get a dip in power whenever it does shift. And I need to be mindful of how hard I'm using the throttle or it was worsen the issue.

Problem started becoming noticeable a month or two ago. Seems to be mostly associated with shifts between gears 1-3. And if I need to gun the engine (I like in Oakland and merge lanes are rare), it has attempted to downshift, try to engage, not, shift back to the higher gear, then try again.

It didn't start suddenly, and has been a slow progression worsening. I first noticed it this summer when I was on a several week road-trip with all my gear in the truck. But didn't think too much of it at the time and figured it was the transmission responding to the extra load. When I got home and unloaded it, the problem went away (at least initially).

T-SB-0092-20 update performed earlier this year. At first I thought the issue was related to the ECU relearning my driving habits in the first months post-update. But it's gotten progressively worse.

Other things that happened not too far before that trip I first noticed were: 1) 30k mile service, but I didn't see anything on the list that might have caused. 2) One time descending a hill, the transmission went to downshift, decided the not to because the RPMS were too high, then decided to anyway and engaged roughly enough that the tires screeched from how hard the shift was.

As far as differences from stock. Truck has 33in tires (w/ suspension) and 5.29 gears. And an additional 450 lbs weight in form of camper and sliders. I'm mindful of payload and don't overload it.

Lastly, I've tried searching the forum for other threads, but haven't been able to find anything specific to this. If there's something that I missed, apologies.

Any thought would be much appreciated. Cheers!

 

It sounds like internal pressure leakage, but I’m far from a transmission expert.

if someone can tag gearcruncher he can have an educated assessment and advice.

if it were me I’d do a pan drop, inspect for damage in the pan, then a fluid fill and adaptive reset as a starting point.

 

Nearly sounds like the same issues my buddy constantly bitched about in his 2019 trd auto but he got pissed off enough, and traded the truck after the dealer told him they found nothing wrong. His tacoma never put out the same power/acceleration from the get go, or a 25 mph roll-on as my 2020 did.

 

@gearcruncher ?

 

upper plenum ACIS connector rod may be broken. ??

 

I think my issue is a bit different (or I'm not understanding your buddy's issue correctly). For me, it's the getting into and out of the gears that's problematic.

Since T-SB-0092-20 (or before with ECT on), truck mostly selects the right gear. And with the regear to accompany tires, it has decent power/acceleration in that gear.

It's bad at engaging/disengaging the trans while switching gears.

 

Yeah, thats different. His truck just had sooner upshifting points than mine even after having the same tsb my truck has. It had no issues going into gear, or shifting to the next one. His truck just wasn't on the same performance level as mine or others.

 

Are you tuned?

 

Me? no tune, but i've been accused of one.

 

You should try getting it tuned, I think it'd help for sure.

 

Thanks so much for the reply! And sorry so slow (long workday).

Mileage is just short of 40k miles.
I'm not familiar with Toyota scanner / scope, but happy to look into if you give me a pointer.

Regarding 5.29s and what I'm experiencing, I changed gears Sept 2021. They were in for 9-10 months before I felt the first thing when driving with load. And didn't notice it in daily driving for another 3 (had gears in for approx 12 months). Would change your intuition about whether a tune would make a difference?

I'm headed to the dealership on Thurs. Will get a tech to go on a drive with me and see what they report.

Thanks again!

 

(Edited for my updated thoughts after I pondered this a little more.)

Hey @mattrent, curious if you ever figured out what was going on with your transmission?

My 2020 is experiencing very similar symptoms. It will occasionally fail to go into gear for a few seconds, then downshift way too hard and sometimes spin the tires. Mine is also on 33's. I bought it used from a dealer and don't know if it was re-geared. I had it tuned (OTT) which improved but didn't eliminate the issue.

Mine seems to be at its worst when starting from a stop on uphill inclines and turning. So maybe it wasn't re-geared or was re-geared poorly?

It's under warranty but I don't trust the dealer mechanics to diagnose it. I'm taking it to my trusted mechanic in January.

 

Solved my issue. Leaving this here in case anyone in the future wonders...

The transmission fluid was almost 3 quarts low. As soon as I added one quart the problems disappeared. Went through the official check and fill process and ended up adding 3 and only needing to drain maybe a quarter quart max. I strongly suspect the dealer I bought it from screwed it up during their "service."

As a side note, to properly check your Taco transmission fluid you'll have to put the truck in transmission temp check mode. If you look on Youtube you'll find a bunch of videos for 3rd gens talking about jumping pins on the OBD. This is unnecessary on 2020 and newer models (also impossible, one of the referenced pins isn't populated). You just start the truck, shift through all the gears a couple times to circulate the fluid, shift to N and leave it for a couple seconds, then shift back and forth between N and D until the D stays on solid. Then shift to Park. The D will then do one of three things: 1) Disappear - you're under temp, wait for it to warm up, 2) D on solid - you're at temperature (between 99 and 120 F), remove the check plug and let it drain until it comes out as a "trickle" rather than a solid stream (if nothing comes out you're low), 3) D flashing - transmission is over temp, turn off the truck and let it cool down. There's a mechanic with a Youtube channel called "The Car Care Nut" whose videos were helpful.

Also, you'll need to bypass the transmission cooler, if you have one, to do the temp check accurately. Not sure what models do or don't have them, but my 2020 OR does. It's as simple as pushing in a "button" type thing and sticking a tiny drill bit or allen wrench through the holes to keep it pushed in while you do the temp check. Don't forget to undo this when you're done.

 

Most likely the previous owner ef'ed up