Trans shift 3-4 flare

I recently bought this used 2017 with 115K on it. After a few days I noticed a 1 time cold 3-4 shift "flare". RPM's jump up several hundred but it's ok after that. I read about the possibility of the trans being too low from the factory but I haven't got around to checking it. I'm a long time German car tech that loves Toyota's and work alot. I just added some Lucas trans additive and now it's gone. Just curious if anyone else had this issue.

Rinnie

 

If you recently bought it the "flare" as you describe may be a learned behavior (The "i" part of VVT-i is "intelligence" it learns driver behind and modifies maps to get best performance and efficiency to driver) stored in the ECU from the previous owners driving habits, I'd recommend resetting the ECU to relearn your own driving style.

Simple to do, just pull the battery terminals and let it sit for an hour or so.

Your fuel economy and throttle response may go down for the first tank or two after which as it relearns your unique behavior.

 

OP, I had the same issue you describe when my truck was new. My transmission came from the factory 1 quart low and I also had the transmission TSB done. I had both issues addressed around the same time, so I am not sure which one fixed the problem. Check out Post #10 on the link below for a copy of the TSB. Good luck.

https://www.tacomaworld.com/threads/new-transmission-tsb-software-fixed-shifting-issues.559737/

 

That is not a complete reset. It can help with some things though. The better / faster route on the battery reset is to pull both terminals (negative off first and on last) and touch them together for 10sec. That allows the capacitors to drain down faster.

The full reset would be clearing the Learned Values for both the engine and transmission. Details on how to do this are in the 1st Post of the ECU Update thread.

 

I agree, that's definitely the better way and that's usually the way that I do it however instructions don't always translate so well via text online when people aren't experienced with that sort of thing and telling people to do that method always makes me nervous because I'm afraid their next post is going to be help somebody told me to short my battery posts together and now my truck burned down.

 

You are not wrong. It was a major issue with folks that have the same bike as mine. Always blowing out ECUs when installing the battery backwards.


I have a bit more confidence with the Taco as it would take some serious fuckage to stretch the terminals to be backward or attach to a miss-installed battery.

 

Welcome to the forum

At 115K I would get some new genuine Toyota ATF and do a fluid change, you can verify the proper fill level following a procedure often discussed here. (I have a manual so I never have studied up on it.)

Here is a thread to get you started: https://www.tacomaworld.com/threads/3rd-gen-auto-trans-fluid-change.548642