Downshift from 6th to 5th at high speed
 

Hi folks,

I picked up a 2013 BRZ a couple months ago, and the first thing I tested on my test drive was to see if this issue was present with this car, and it was not. However, a couple days ago I had the dealership perform transmission service and now it has the same issue my first BRZ had: when you shift from 6th to 5th at 70mph+, there's a synchros crunch.

I'm going to have my local mechanic put Motul 300 to see if resolves the issue, but a question, how many of you had this issue resolved by the tranny fluid?

Thanks!

reading other's responses on WHICH fluid relieves symptoms is hit or miss. possibly due to local climate conditions, but not telling if brand mentioned will solve problem.

If it wasn't there before the service but was after then changing the fluid is probably not the answer. What was the "service"? What could it have changed? I would talk to whoever performed it and see what they have to say before I did anything.

All they did was replace whatever fluid was in there (no way to know) with the OEM Subaru fluid. They did both the transmission and differential. Nothing else was done to the car.

Ahhhhh. Well in that case then maybe the different fluid would indeed be worth a shot.

My '13 was completely fine until 15k when I had Toyota flush out tranny/diff fluid. I got 65k now and 5th gear still grind but I just live with it.

This is what I do to minimize grinding:

* Precise and quick shift and no granny shift.
* No rev match shift. Yes, my 5th gear hates rev match.
* No down shift above 3k.
* E85 also minimize 5th gear grinding. Weird right? But it does helps..

That is very weird. Any theory on how a different fuel affects the shift?

Hate to say it but no down shift above 3K is unacceptable. If you want to speed up when you're at 70mph and can't downshift, then you might as well drive a Prius... :lol:

Worst case scenario is I'll do the same as I did with my first BRZ, request a new transmission from Subaru. But the process is a pain in the ...

I'm not sure but E85 vs 93oct is like night and day for both engine and tranny. Im struggling with my clutch work on 1st from stop with 93. But it's butter smooth with E85..

I get the engine but am baffled how it has any possible impact on the tranny.

My wild guess is that smooth engine means smooth tranny?

Pretty smooth engine on gas too though. Maybe somebody will jump in and enlighten us (thank god Gforce/the Ubertwins can't).

I just floor it on 6th. It's not that bad at 70mph on E85 lol. But then mine's got about 25hp over stock :)

The only times I can think of needing to downshift at 70+ mph is 1) Emergency 2)Track racing and 3) driving like an asshat. In the time it takes me to rev-match, downshift and floor it, gaining the necessary speed to pass, I can just put the pedal down in 6th and be going as fast as I need to, frankly. Might as well save your clutch if you are just on the highway.

p.s.--the fuel does not come in contact with the transmission, which is what I think @Tcoat is trying to get at. The assertion that E85 somehow makes your shifting smoother is pure butt dyno.

EDIT: This is with my stock FR-S. Using e-85 or FI, even a tune might change the most effective parts of the powerband. That said, still seems unnecessary to me.