[Bktwo24]

2nd that, shadowtrench is 100% correct and that is your problem. I learned that like genny26 did…the idiots at the shop that balanced my tires reinstalled the staggered rims incorrectly front and back. Messes with the wheel speed calculation and thinks they’re slipping. The calculation “error” doesn’t become large enough to activate tc until you’re at highway speeds. Getting on the accelerator hard while going ~65+mph will immediately trip it.

You didn’t mention, but did this problem happen to start soon after you installed the new tires with the improper ratios?

P.s. now is the perfect time to change your tranny fluid if you plan on keeping the car longterm

Also I don’t really have service records of the car and don’t know if it has ever had the trans fluid changed. I know about horror stories with other cars that sometimes changing the fluid makes it shift worse because the metal shavings that flake off in the trans over time with use get flushed out and they provide “cushioning” in a way if you know what I mean. That’s why I’ve been so hesitant towards doing it. I’ve been told sometimes it’s best to leave it if it shifts fine. Which it does shift well overall but sometimes there’s a gimmick between 2-3 and 3-4.

 

[Bktwo24]

So stock was 225/40/19 (2080mm)and 245/40/19 (2131mm). So + 2.3% increase in circumference.
Now you have 245/40/19 (2131mm) and 265/35/19 (2098mm). So -1.5% difference.

You have increased the front wheel circumference and decreased the rear. Your rear wheel needs to rotate more than your fronts now to travel the same distance which means a different calculated speed. Now the calculations think you are spinning because the percentage is no longer in spec. The reason you see it at Highway speeds is the wheel speed difference measures higher the faster you go. Typically 80mph is the point when speed readings can be off by 1mph. At lower speeds they aren't as drastically different.

So if I were to change the front tires to a 35 sidewall would it solve the issue the same as if I were to change the rear to 40 sidewall? Also I have the option to pickup some stock Supra tires, 255/35/19 front and 275/35/19 rear, know if that would even fit or rub? Car is only lowered an inch or so.