Problems shifting from third to second
 

Hey guys,

I was at an AutoX event over the weekend, and experienced an odd problem with my car. I tried searching for the issue, but couldn't find anything solid, so my apologies if this has been addressed before. This is basically what would happen:

The course was much faster and wide open, and required to go into 3rd gear for this one. I'd shift into 3rd gear, and would try to shift back down into 2nd turning ever so slightly before a chicane, that turned into a hairpin afterwards. This is where the issue showed up. When I would try to shift down from 3rd to 2nd, right before the chicane, it felt like the gate for 2nd wasn't even there, and was just a wall. I would then coast through the chicane while fighting to get into 2nd gear, and then only right after that element, there was a spot where I could point my car straight, and only then would the car go into 2nd. Happened every time. Driving home from the event, and driving into work today, the car shifts normally and with no issues at all. 2nd gear has always felt a little clunky, it's not buttery smooth like it is going from 3rd to 4th or anything, but it's been like that for as long as I can remember.

Is this a normal thing with the car and I just need to adjust the way I drive, or is this a known issue? I run with the Kartboy Short Shifter, but that's the only mod that I can see that would cause this problem. Transmission oil hasn't been changed, no shifter or trans bushings or MTEC Springs or any of that jazz, just the short shifter.

Thanks beforehand for the help, and sorry if I posted in the wrong area, I figured the AutoX community could better help me understand this issue.

Were you heel-toe'ing or otherwise rev-matching the downshift?

I was. It's not perfect, by any means, I usually get within 250-500 rpm off the correct spot when I do mess up my heel-toe, but it was there. I would try to heel-toe right before that chicane, wouldn't go in, so I'd coast through rev-matching trying to get 2nd to go in.

Ah ok. I was going to suggest that if you weren't already doing it. You probably know this already, but just to confirm, you want to rev-match before you slot the shifter into the gate.

My transmission can be notchy on cold upshifts, but it's very smooth on downshifts as long as I heel-toe/revmatch.

Yeah, I've always rev-matched, and if the car is going straight, it's fine. I'm just wondering if the high rpm's mixed with the slight cornering is normal with all cars, or if it should be going into 2nd, and just isn't.

Unless you're double clutching it (clutch in, put in neutral, clutch out, rev, clutch back in and get into gear), it won't have a single effect on how it goes into gear. Heel/toe without a double clutch is only so that when you release the clutch you aren't having to bring the engine up to speed with the clutch (and possibly locking the drive wheels).

More on topic, how is downshifting to 2nd under similar situations but not mid corner? ie - is it possible you're just missing the gate while cornering?

I'm with wparsons. You sure you didn't just miss the gate? I can heel toe on the street no problem. I can heel toe at the track no problem. At an autocross? Things are a little more hectic and it's harder for me to get it right if I'm busy managing my other inputs to the car at the same time. Things don't always work quite how we plan in the heat of battle.

I'm notorious for banging gates in my friend's car like they're bent over the table asking for it. And I get to autocross that car regularly enough. For me personally, muscle memory is everything when I'm shifting and something as simple as moving my seat forward or back can throw me off. If that shifter is a new install, you might just need more time with it.

How many miles on the car? I had a crunch/grind going into 4th gear at high RPM which resolved itself after 7,000 miles or so. If your car is still pretty new it may change character a bit as it wears in.

I don't have a real answer here but I have experience something similar on a different car. From what I gather the transmission mount is somewhat flexible and it appears the rear attachment point of the shifter is mounted to the body?

That being the case it could be that under certain cornering loads the reverse lockout plate might be preventing you from moving the lever far enough to go to 2nd gear?

I have seen the install thread for the Kartboy lever and I know the lockout plate is adjustable, and it seems like moving it further to the left might help the problem. The trans mount insert and rear shifter bushing may help, too. I'm not really trying to sell you parts but I would guess this is what that trans mount insert is designed to help.

Thanks for the responses guys! The car shifts fine into 2nd every other time, this is the first time I've experienced the issue. I'm pretty sure I wasn't missing the gate, because I sat there coasting trying to get the shifter to go into the gate, but it just wasn't there. At one point, I just held the shifter against 2nd with the clutch in, and as soon as my car was straight, it "fell" into 2nd gear.

The car has just over 7,000 miles on it, so that could be part of it. I've also been looking into getting some new transmission oil, I figured that'd probably help. I know the reverse lockout has caused some issues before, but I have it mounted as far left as it can go, as recommended in the Kartboy install thread. The shifter has been installed for over 6,000 miles now, so it should be fine. With the exception of the slight crunch going into 2nd, it's completely fine otherwise.

There are cars where the OEM engine and transmission mounts are such that, when turning, it's very possible to miss an otherwise totally makeable shift in the way the OP describes; or, much worse, money-shift it by doing a 5-2 or 4-1 downshift. This happens with some frequency on BMW E36 M3s, and almost always results in a lunched motor. I see it at least once every year.

I wonder if @CSG Mike or anyone else can speak to the likelihood of this occurring with the twins.

If you were actually hitting the gate, you might just be feeling the resistance of the 2nd gear synchro, which will feel like a wall until it's job is done.

The synchros are like little clutches for each gear to speed up/slow down the transmission input shaft and clutch disk.

When you're downshifting, you're using the synchro to speed up the tranny input and clutch disk. If the shift is delayed, the tranny input shaft speed will fall too low, and the gap becomes huge and the synchro has a TON of work to do.

Rev matching at this point has no effect, because you're only revving the clutch plates, and they're not connected to the transmission until you let the clutch pedal out. The tranny input and disk is free spinning, slowing down further until the synchro generates enough friction and forces the shaft to speed up and it clicks into a gear.

As wparsons mentioned, using a double clutch will engage the clutch in neutral, which will use the engine to speed up the clutch disk and tranny input, so the shaft is brought up to speed and the synchro doesn't have to do anything. Then, gear engagement is effortless.

I haven't had any issues... a lot of it can be attributed to a newer driver not being used to having lateral G acting on them *as theyre shifting*

Proper shifting technique should eliminate this.

Hey Mike, want to show me how to drive sometime? :D

I am pretty new to AutoX and all that jazz, but I haven't been doing too bad, usually placing 1st or 2nd in the Novice class, and I have done a total of 4 events. I was sure I was handling the situation correctly, but I couldn't get an instructor or anyone else to drive my car Sunday morning to see if anyone else ran into the issue with my car. Another BRZ driver had the same issue, but maybe we're both doing something wrong? :iono:

Are you running the stock rear transmission mount? I know I can feel my shifter move around A LOT over bumps (STILL haven't installed the mount insert sitting in my garage :( ), if it's moving under lateral load it could be moving enough that it's blocking the gate. I'd look at this, especially since you mention that once you straightened out it went in no problem.