Hesitated up-shift, Normal or WTF?

Started to notice a couple of months ago that on when i accelerate on an incline, the transmission hesitates to up-shift from 4th to 5th. Increase of the throttle, decrease the throttle, braking, nothings helps. It will only shift if i induce it manually or once i crest the hill. This issue can not be replicated going downhill or on flat plains. I have taken it to the dealer for diagnostics with not success on finding anything wrong. i do have over sized tires, yet this is a problem that started long after my conversion to over sized tires. I have no codes and 86k miles. I have reset my ECU multiple times and even changed my tire size. Any ideas?

 

Without driving it, I would be hard pressed to give you a solid answer. That being said I will tell you that I have driven several Toyotas (Not just the Tacoma) that do this exact same thing when shifting into OD. Oversized tires can increase this issue, though I do note you said it started long after the conversion. How steep of an incline, and how fast in MPH are you going on average?

 

Thanks for the prompt reply. This is my 4th Tacoma, one of which i sold at over 350k miles. I have never had any issues with Toyota transmissions. Hence my repeat purchases. This issue prosiest at any speed i would say above 45 m/ph. The degree of incline varies. but I notice the most on just simple on ramps to freeways both after start up and after the transmissions has had time to warm up.

 

I would suspect the dealer is not looking in the proper place or spending enough time to properly re-create your issue .They need to break down each individual sensor and watch the parameters on the scanner . Only then would I suspect a mechanical hydraulic issue

There are a few parameters that have to be met before the transmission shifts into 5th gear and they are all computer controlled , however this doesnt mean that the issue will set a check engine light or code . The computer could be commanding the transmission to upshift into 5th gear but the mechanical valve body has to respond to the electronic command .
Is the vehicle at operating temperature ? What does the pcm see when the issue occurs
Is the transmission at operating temperature ?What does the pcm see when the issue occurs
Throttle position sensor - if the pcm sees your foor to the floor - no 5th gear What does the pcm see when the issue occurs .

Also agree with Bamatoy . These transmissions have delays upshifting to 5th gear
Does the computer know you are actually in overdrive ( gear selector could be out of alignment ) .What does the pcm see when the issue occurs
Does the brake switch function correctly ?What does the pcm see when the issue occurs
Does the speedometer function correctly ? What does the pcm see when the issue occurs
Does the input speed sensor and the output speed sensor function as it should . Some times these drop out and the pcm doesnt catch it .What does the pcm see when the issue occurs
These are the 6 basics that the pcm needs to see before it will allow the trans to shift into 5th gear . Then there are the mechanical hydraulic components of the transmission that have to respond to the commands of the PCM in order for the transmission to upshift

 

I think it is the nature of the beast. Mine does it on one hill every time and will not shift out of third. Same thing, leave off the gas, hold steady, or give it more gas it won't shift out of third. After I slow down for the next corner, it shifts fine.

 

The 4th to 5th shift is nothing like 1 2 from the factory... Its smoother and the only way for this to happen is for it to slip. I've had a tech with me with his techstream lappy with him as I drove hard and he monitored temps and solinoid readings. Those laptops with the proper software and membership levels yield some awesome data.

We were able to recreate it 1 time and everything looked fine on the software.

I have noticed that disconnecting the battery negative terminal for about a half hour seems to clear any of the settings of the transmissions "memory" or whatever the right term is. The trans iirc is supposed to learn to an extent your driving habits.

I think that cresting a hill is an odd thing for the trucks computers to figure.... If u hold it in 4th till u crest, it may be assuming ur still climbing and it would want to allow some slip instead of going into lockup so it can raise the rpm. So switching from 4 to 5 as u crest may confuse things.

Manually shifting just before u crest will cause it to wanna kickdown or slip to raise the rpm as its still under load from climbing also.

Shifting after u crest and u let off the gas, the computer may be trying to activate injector shutoff and then u throw it into D which might confuse things as I think it locks up while using injector shutoff to make use of trans/engine braking instead of cooking the transmission.

When letting off the gas, I think the rpm drops to a certain point and injectors shut off and then come back online to a degree after hitting a certain rpm. I did some reading the other night but I was very tired. Shifting at the right point manually may throw a wrench into the game as the truck went from lockup and engine braking to u upshifting which like I said earlier is a sloppy shift and let's the trans slip and rpm fluctuate for a second or two.

There's also the possibility ur trans was getting hot depending on the grade/speed/ grill obstructions/ length of grade/ number of recent grades and ambient temps.

Another factor..... When is the last time u had a trans drain and fill or flush?


In the end, I suggest asking a tech to ride shotgun again and ask him if he can monitor things through his laptop as u drive. They can change some settings like lockup to try and narrow down the problem.


Free item to try tho, is the battery negative terminal off for 30 minutes... Could be purely psychosomatic but I swear I felt the trans alter its shifting characteristics when I do this.


A Lil medicated right now, I hope that wasn't all just jibberish to ya.

 

get a scangauge II and setup the trans temp code... the scangauge is a very handy tool. So is the ultragauge, but it doesnt offer any kind of trans temp readout... If it did, I woulda kept it due to the parameters per page vs the scan gauge.

 

Shortly after my original post I took my taco into a local Auto Transmission shop. To no success were the able to determine the problem with simple diagnostics. Their intentions were to keep my daily driver for several days to try and simulate and diagnose my issue, even after I took a tech on a ride along and reproduced the shift hesitation twice. Better then the Dealership Techs justification to the issue of the tires being to large.
Regardless I continued doing some more research into the source of this problem. Caught knowledge along my journey thorough the forums that a dirty TBV can produce erratic shifting in low gears. After investigating this issue, of course the TBV was dirty. Cleaned that and also discovered the MAF to also be dirty. Cleaned both delicately and reinstalled. reset the ECU, and long behold problematic shifting issues ceased to exist. Situation Normal. Appreciate all your input fellas.

 

Good to hear! Thanks for coming back and updating this thread with your successful solution.

 

***Update*** Sorry to report that the issue had started again. Only this time it seem to happen on any degree of incline, even on a straight away. I have pulled all wheel sensors and checked resistance and cleaned then, also did the same with the Transmission Speed Sensor, and all seem to be checking ok. Next Im dropping the tranny pan and changing out the filter, not so much a flush but ill blow all the lines out with low psi. The hunt continues!

 

************Update*************
So Dropped the pan and changed the tranny filter. As I had stated in my original post, dealer diagnostics found nothing to be wrong. Mechanic stated that the fluid level had checked good and just as important the condition of the fluid looked good as well. Upon my own discovery the fluid at close to 90k (with out towing) looks black, but not gritty. Magnets had not collected any metallic but the fluid was thick, maybe a little thinner then tomato soup. Most important was the fact that i dumped only 4 quarts out and had to put 5 back in the tranny to achieve a good level. Although the hesitation has seemed once again to calm down. Its to premature to determine if it was a solution. I would recommend that others check their tranny fluid if in access of 60k+ miles. I have heard 60k, 80k, 100k, 120k miles for fluid change intervals. Most resent out of the Chilton Manual 30k miles. Choose your poison, for me ill be paying more attention to the "sealed unit" transmission fuilds. Furthermore, the cork gasket that was sealing the pan was completely deteriorated, and the pan bolts were all under torqued. If you do this job i would further recommend FIPG (orange) from Toyota, as the cork gaskets are garbage.

 

Not sure if you have read through this post . Might help
http://www.tacomaworld.com/forum/te...hift-kit-shift-recalibration-kit-2nd-gen.html

 

Ive been calling and calling and all the dealerships say is that the Tacoma is designed to shift this way. when i can almost guarantee it isn't. it will shift three times low and high to just go up a simple hill and even when i throw my foot into the pedal it will decrease speed by 10mph until it downshifts then it acts like im flooring it. and just to check on this issue even though its under warranty they want 140 to fix it. its bullshit and they claim it to be under the "luxury shift" feature more like luxury shit feature. my first and second gen pickups never had trans problems this is my first new vehicle and other than the fact of it looking pretty im not 100% satisfied. put the same amount of lift on my 80's yota and put Billie yellow bodies and the ride will be 100 times better in handling. i had to disconnect my sway bar on my new one just so my head wouldn't hit the damn window when i entered a driveway a little bit at an angle. horse power is nice and it sounds pretty but honestly if the trans cant put it to the ground and the suspension is throwing you around all over the place where is the enjoyment?im a diehard Toyota fan but i have some questionable doubts on this new Tacoma. has anyone looked at the arm angles for the wishbone( a-arm) front end? a wishbone should be parallel but they angled it to give more pressure hence the reasoning to beef up the spindle and upper ball joint the reasoning for these angles it to prevent squatting in the front end but it also limits the droop i would take a lil squat in the front end vs nose dive from fully drooping over a damn rain gutter crossing the road or a speed bump for that matter. my second gen with the wishbone had parallel arms and with a shallow bump and shallow top out stop i pulled almost the same amount of travel as the new mid travel kits for these with stock components! they should realize that the dirt and desert will be a harsh terrain so if they built something that can hold up amazing in the dirt like the old school pickups they should probably stick to it. the trx or whatever its called isn't the truck i described either i looked and almost bought one then was disgruntled when i saw its just a normal trd with bilstein 5100 series shocks, others will argue that they are 7100 series but friend, measure the body diameter. its a 5100. just a few frustrations and some word for thought.

 

All right, another update… I just may have finally got to the bottom of this whole shifting ordeal. Wish I would have considered the solution before but, hind sight is always 20/20. If you are experiencing the problems from the OP, and are running a CAI (like I was) I would suggest removing and replacing it with an alternative intake system. I chose to just replace it with the stock system. Which now that I have it on and parameters are starting to fall back in place I can say that the CAI is a huge waste of time. In less you are running FI. I was not producing any codes of any kind. I did the following to my engine:
Dropped Tranny Pan changed filter and WSF (which was short one quart)
Changed Spark Plugs
Changed thermostat (changed while replacing water pump)
Swapped wheel speed sensors (Front to back)
Checked the charging system
Cleaned MAF and Throttle body valve (most promising result)
Checked resistance on transmission speed sensor
Monitored all changes with scan gauge II
Finally I changed back to my stock intake and instant results of normal shifting points. I have talked to many individuals with this same type of problem. If you are not running a CAI I would suggest doing any of the following on the list. Start with cleaning your MAF and TBV. And of course after trying anything always disconnect your battery for at least 10 mins to reset ECU.
Happy Hunting