Slow RPM Buildup and weird shifting sound
 

Hey guys, i need some help diagnosing my car's problem, it currently has :

Fully Catless Header-Back exhaust (exc. Overpipe still stock)
Tuned with Dastek Unichip Q4 Piggyback
HKS Inlet Tube
HKS Drop in filter

The rest is pretty much stock. Ive got the tune 2 years ago without any problems, but in the recent months i noticed that when accelerating, WOT from 3rd to 4th gear, the RPM doesnt climb straight, it even drops for a second before starts climbing up. And it makes an unfamiliar shifting sound everytime i shift near redline on every gear, its just most noticable on 3 to 4th.

It happens if the car's quite warm after 10 mins driving redline, but i think it also happens even when the car's relatively cold. I cant remember since when these things happen, but im pretty sure its not like this even after 1 year since its tuned.

I showed the video to my tuner, and he said its the AT being too hot but why does it happen on an NA car ? or is it an ATF issue ?

Video :
"https://youtu.be/KFM14jSY4Rw"
"https://youtu.be/UHcsrUdXnx4"

ps : Speedo is -10% off due to oversized tyres, 235/45 and 255/45 on 18" wheels

I'd suggest you do a complete flush of the AT and put in new ATF.

:iono:

is complete flush the same with drain and fill ? because ive heard people say that this car should never be completey flushed because it'll damage the fins or smt like that.
I also changed the ATF by doing drain and fill just once last year, using total LVMV atf recommended by the workshop since i cant find suitable motul/redline atf here.

in my case, should i continue drain and flush with the same total lvmv or try to find motul/redline?

What I was getting at with my use of the term "flush" would be to follow the procedure in the maintenance manual which has several steps, not just to drain it out and refill.

As far as what ATF to use, I'd just use whatever is within spec as suggested by the manual.

I don't have an AT so, I never looked into it.

Hopefully others will come along with some good advice - ;)

Back in the day ..... hmmmm ..... back in my day, average cars didn't have automatic transmissions. - :iono:

afaik the total lvmv meets the specifications as stated in the manual, any idea why this problem still exists ? i did the atf change last year, but as far as i remember this problem exists way before that.

i live in indonesia where the weather is quite hot, but there are lots of other places hotter than here, yet i havent seen any threads about a problem similar to mine :iono:

Well, I don't know what to tell you, Blackedout86 - :iono:

My only thing was to suggest fresh ATF or have the transmission rebuilt. However, with these cars, I understand there is a little computer thing that tells the transmission what to do when. Maybe it needs to be looked at?

If you want to completely flush the ATF, you'll have to do drain and fill 3 times.
https://www.ft86club.com/forums/show...55&postcount=1

One member here had some issues with the clutch slipping at the track and he elaborates on what happened on this post, but he is also boosted.
https://www.ft86club.com/forums/show...t=18868&page=7

im taking the car back to the tuner who installed the piggyback, i surely hope its just something wrong with the tune lol. If its not then flushing the ATF is my only hope since rebuilding the trans is impossible here.

reading the clutch slipping thread makes me nervous, i cant even find the recommended ATF ive seen in this forum like motul gear 300, redline d6, eneos, lucas etc for this car here, let alone finding a workshop that can rebuild the trans.

the car is relatively rare here, subaru's official workshop is closed permanently, i even once took the car to toyota dealership for general maintrenance and the mechanics asked what car is the 86 ? man i took off right away, true story.

If this can be fixed by flushing, im looking at a dead end.

His case is an extreme scenario. He was tracking hard on a 100+ degree weather and his coolant temp was also very high. AT uses the coolant to warm up the transmission on cold startup, but this also affect the transmission negatively when it's overheating.

You can flush with Toyota ATF WS and be fine. No need for fancy brands if the transmission isn't seeing extreme heat

Flushing an automatic isn't too bad. While I don't know how/where/whether the drain & fill bolts for BRZ/86 automatic transmissions exist, this is what I did on a Mazda/Ford auto transmission:

Find the transmission oil drain bolt. If it doesn't have one, I suggest taking the oil pan off. That way you'll clear out any gunk as well. While you're there, also change the filter. Let the oil drain overnight. It will be a lot. Turn the rear wheels (if possible) to turn the torque convertor while in Neutral, to get out any hidden oil in the TC. If you can measure how much oil has been drained, you can add the same amount back in through the trans dipstick tube (if it doesn't have fill hole). If not, keep adding slowly until you reach the dipstick tube mark.
Most likely you'll end up filling too much oil. Please make sure you have a suction pipe to pull out any excess oil. This will be a patient weekend project.


HOWEVER, if it is one of those "non-serviceable" transmissions... well.... have fun doing something else during that weekend instead. Not worth sacrificing a fun weekend.

Can you post a data log?

If it is because of the trans fluid here is the procedure, much simpler version. the manual makes it look 10x more difficult then it really is. I have done this at least 8 times now. basically 1 more step than an oil change really.

https://www.ft86club.com/forums/show...2&postcount=12

Do you not have access to toyota ATF fluid?

The noise you mention reminds me of the goose honk you get sometimes on manual transmission with a bad throwout bearing.

Honestly yours doesn't sound bad and its awesome to see someone banging gears at redline in the auto. But keep an eye on it to see if it changes.

im currently using demineralized water + a little prestone super concentrate for coolant, should i replace it with prestone prediluted 33% instead ? will it help somehow ?

i have actually done atf change once last year using total mvlv, because i was trying to fix this issue. apparently it doesn't help, so i doubt its an atf issue.

i even tried unplugging the Piggyback, so the car is basically stock tuned, but the problem still exists. so thats not a tune-related problem either.

Your coolant will have nothing to do with this.

so you followed the leveling procedure exactly?

A data log is one of the best tools for finding and narrowing down mechanical issues. not just tune issues. Regardless stock tune or not. It is a good starting place. Not to mention you said you are using stock tune with aftermarket header and no cats?

what piggyback where you using?

Using tires that are so far off from normal stock diameter tires and especially different diameter front and rear. Can cause the ecu to calculate thing weirdly causing weird issues. Especially how the ecu calculates torque values for the AT shifts. When did you get these tires in correspondence to noticing this issue?

also you have an NA auto 86 with 10% taller tire (which presumably is pretty heavy vs stock wheel/tire) you just don't have any power now in 4th gear with 10% taller tire, your mechanical torque to the wheels is so low now any incline in the road and or gust of strong head wind can actually cause you to temporarily decelerate especially between shifts specifically 3-4.

The only noise i hear is possibly an exhaust leak that is exacerbated when exhaust is warmed up and when shifting because it "blips" the throttle.

i forgot exactly how since it was last year, but it was something like 3x fill and drain, according to the complete atf guide on this forum. I will try to get data log from my tuner for accurate results, but it takes some time, in the mean time i'll try to find any exhaust leaks.

im using dastek unichip, and yes the tyres mess up those things but i can barely feel it, and they were replaced just last month, this problem much longer than that. i was using 225/40/18 before.

The rpm drop was more like the car hesitated to rev and held for a few seconds, because i also tried WOT on downhill roads, it still occurs always after shifting at high rpm, not necessarily redline shifting. but after that it accelerates just fine, going up all the way to 210kmh+ on speedo (prob. 225 actual).

It goes like (roughly) : WOT 3rd gear =>shift to 4th on 7,2k rpm which drops to 4,5k =>going UP to 4,8k then boom it drops back to 4,5k => Going up again normally

not to mention the awful intake growl sound from 4k rpm and up.

The leveling procedure is different then just drain and fill x times, it requires getting the trans to a specific temperature range (between 108f-117f) and then leveling it to the specifications by pulling the leveling plug. Not something you would really forget if you did it or not.

A datalog could help narrow this down a lot, either finding the issue, or eliminating several possibilities.

You can also tune how the Auto shifts, making it shift quicker, and bite harder/firmer, etc.. Alternatively an upgrade valve body will accomplish this as well, but even more so.

Depending on mileage and how you drive it is possible clutch packs could be wearing and slipping. but i think something else is at play here.

i took the car to my regular workshop for the atf change, i showed the complete DIY atf change on this forum to them and asked to follow it completely including the levelling, which as far as i remembered they did.

If it means anything, i just remembered the car went on limp mode once because of backfiring tune (which apparently this car hates so much), and the car goes exactly like the video, minus the CEL. after clearing the code it went back to normal after a few hours, and it never happened again until this problem occured some 2years ago.

Also in limp mode, the car held back when downshifting, similar to fully disengaging the clutch on a manual car on high rpm, but it doesnt happen on my current problem.

So basically my car is in constant limp mode minus CEL and hard downshifting kickback.