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Old 05-30-2016, 12:43 AM   #1
barryl80
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Default Accidental downshift on highway

Hey all

So I was driving on the highway a couple of nights ago somewhere between 60-70mph when I tried downshifting from 6th to 4th gear... except I went into 2nd instead. When I let off the clutch the RPMs immediately shot up and the engine revved hard. I put the clutch back in within a second, or at most two and went back into 6th. I don't think I fully let off the clutch either. It's a new 2016 WRX with barely 500 miles (still in break-in period!) on it so I'm hoping I didn't do any damage. Everything seems to be fine both driving and idling - no weird smells or sounds, no smoke, no burning clutch smell. I heard a clank in the rear a couple of times after this but I'm almost sure that's been there since before this happened.

So here is my question: What were my RPMs at when I downshifted to 2nd gear from 6th at 60-70mphs? I only had a split second to look at the tach but but I think I saw the needle at about 6500 (I may be completely off here) or so and it just stayed in place. I just wanted to confirm this since I'm worried I may have gone into or past the redline... like 8k+ or something. Also, what kind of damage should I be looking out for? There is a very subtle vibration in the clutch when I press or release it, at about the bite point. This only happens if the car has been off for many hours (4+?) and goes away after using the clutch pedal a few times. I'm not sure if I'm just out looking for problems now and this was there when I got the car lol.

Anyway thanks for any help
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Last edited by barryl80; 05-30-2016 at 02:26 PM.
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Old 05-30-2016, 01:30 AM   #2
just slothing
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according to my cackle asians somewhere between not-high-enough-to-break-it-obviously and 19000 rpms.

this has happened to me at least several times each in many cars and none of them ever had tranny failure or trouble.
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Old 05-30-2016, 01:47 AM   #3
powder8
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if something breaks take it to the dealer and tell them its broke and you don't know why. if your car isn't modded chances are you'll get whatever it is fixed for free. excluding of course brakes tires suspension and other "wear" items.
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Old 05-30-2016, 05:37 AM   #4
Jkmaynard
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Don't worry about it your under warranty drive the piss out of that thing trust me no matter what you do it's a boxer engine and they bite the dust eventually my 06 I did there proper break in and it still crapped out at 84k going from a stopped light moving about 15mph 4th cylinder took a crap...
So for giggles my brother has been driving the hell out of his 07 from mile 1 brand new to 138k and nothing me I drive my 05 sti like I stole it granted it has a built motor still if you broke something take it in you have 500 miles on it lol
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Old 05-30-2016, 09:29 AM   #5
mishapopa
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Ouch... You should get a short throw to help avoid missing gears. You've definitely gone well into the redline.
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Old 05-30-2016, 06:26 PM   #6
MaddMax
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Go into 2nd gear and get up to 35mph. Look at your rpms and multiply by 2 to get the approximate rpms at 70mph. It's my understanding that the 2015+ WRX can do 61-62mph at the 6700rpm redline. Based on this, it sounds like you maybe exceeded redline by a few hundred rpm assuming you fully released the clutch. Given this, I highly doubt any damage was done. Typically if someone misshifts, the damage is immediate, heard, and felt. In many cases the valves float and kiss the pistons or the clutch blows up.

Next time you want to grab a quick shift into 4th from a taller gear, simply push the shifter into nuetral, invert your hand (thumb down) and pull directly back. It should slide easily into 4th and keep you from pulling to the left and into 2nd.
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Old 05-31-2016, 01:51 AM   #7
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Again the car is fine if you fudged anything up it would of manifested pretty much instantly
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Old 05-31-2016, 06:23 AM   #8
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What were the rpms?
Uhhh, WAY too high if it fully engaged, which it may not have.
Nothing you can do about it now, you probably caught it when the clutch was still slipping because honestly if you threw it in 2nd at 70 I'd guess you'd blow the motor if it fully engaged.

You should start by never skipping gears again until you get more experience with stick and/or this particular car. Go to 5th next time.
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Old 05-31-2016, 07:18 AM   #9
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Quote:
Originally Posted by just slothing View Post
according to my cackle asians somewhere between not-high-enough-to-break-it-obviously and 19000 rpms.

this has happened to me at least several times each in many cars and none of them ever had tranny failure or trouble.
There is not really any way that you can damage a transmission from a mechanical over rev situation.

The issue is the motor. The valves start to float somewhere around 8k or 9k RPM. When that happens, your motor destroys itself because the pistons smash the valves.
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Old 05-31-2016, 07:21 AM   #10
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Quote:
Originally Posted by rtv900 View Post
What were the rpms?
Uhhh, WAY too high if it fully engaged, which it may not have.
Nothing you can do about it now, you probably caught it when the clutch was still slipping because honestly if you threw it in 2nd at 70 I'd guess you'd blow the motor if it fully engaged.

You should start by never skipping gears again until you get more experience with stick and/or this particular car. Go to 5th next time.
You can guess all day long, but you'd be wrong.

If he was going 70mph, and shifted to second, he's only 5mph faster than the car is geared go in second.

That really isn't enough RPMs to float the valves.

It would take going into first at 70mph to really **** yourself.
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Old 05-31-2016, 08:41 AM   #11
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Quote:
Originally Posted by Annihilator817 View Post
You can guess all day long, but you'd be wrong.

If he was going 70mph, and shifted to second, he's only 5mph faster than the car is geared go in second.
fair enough

my 'opinion' is that 5 mph faster than redline, or a few hundred rpm I guess over redline on a BRAN NEW motor is way too fast.

and again, what's done is done, hopefully its fine.
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Old 05-31-2016, 08:44 AM   #12
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It was done to mine at 7k miles.

Into first gear from the top of 2nd (65mph).

My motor is healthy at 50k miles.
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Old 05-31-2016, 10:38 AM   #13
Gallo2011
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Find the video of Tommi Makinen on the Nurburgring in the white STI. He shifted from 5th to 2nd and briefly revved the engine to about 8500 RPM. Didn't even blink and the car didn't either.
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Old 05-31-2016, 10:45 AM   #14
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As for Makinen not blinking, getting back on WOT immediately after a mechanical over rev is thought to have a chance to save the motor. A sudden rise in cylinder presses might be enough to bend the bent valves back.

I know its been done on BMWs many times.


This is a video of my car, the mis-shift occurs as the car passes through the finish gate.

To be honest, I'm extremely surprised there was no apparent damage.



Last edited by Annihilator817; 05-31-2016 at 11:20 AM.
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Old 07-12-2016, 12:50 AM   #15
J2Rad
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Just picked up my 2017 wrx last month, and I've done the exact same thing. Coasting in 6th @ 70mph and trying to quickly downshift and rev match to 4th. I knew it was in 2nd as soon as I heard the engine start screaming at me. Really only a half second and it never actually hit red line. But still it's a little unnerving. Really thinking about installing the brass shift bushing and shift stop as my very first mod. I've read it significantly improves the feel of the shifter.
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Old 07-12-2016, 06:21 AM   #16
rtv900
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Quote:
Originally Posted by J2Rad View Post
Just picked up my 2017 wrx last month, and I've done the exact same thing. Coasting in 6th @ 70mph and trying to quickly downshift and rev match to 4th. .
I love the 'rev matching' thing people think they are doing.
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Old 07-12-2016, 07:15 AM   #17
Notbrick
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I'm questioning the circumstance need to shift from cruising speed in 6th gear to immediate 4th?
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Old 07-12-2016, 08:04 AM   #18
rtv900
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Originally Posted by Notbrick View Post
I'm questioning the circumstance need to shift from cruising speed in 6th gear to immediate 4th?
The circumstances would be somebody thinking they need to launch the rpm's up to 5000-5500 in order to rip past someone or just accelerate insanely fast up to triple digit speeds.
In other words, no rational reason at all.

What I can't understand is how someone could 'think' they are taking the extra time to 'rev match', yet be so hasty as to throw it in 2nd by accident.
No idea how one pulls that off, or why anybody would do something that quadruples shift time to rev match on a synchronized transmission where you wouldn't even know if you did it right anyway. . . . .because you know. . . .it's SYNCHRONIZED!
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Old 07-12-2016, 08:12 AM   #19
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Originally Posted by rtv900 View Post
The circumstances would be somebody thinking they need to launch the rpm's up to 5000-5500 in order to rip past someone or just accelerate insanely fast up to triple digit speeds.
In other words, no rational reason at all.
That's where my thought was going. We have quite a beautiful 5th gear right above it.
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Old 07-12-2016, 10:06 AM   #20
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Originally Posted by Jkmaynard View Post
Again the car is fine if you fudged anything up it would of manifested pretty much instantly
x2^^^
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Old 07-12-2016, 11:07 AM   #21
J2Rad
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Quote:
Originally Posted by rtv900 View Post
The circumstances would be somebody thinking they need to launch the rpm's up to 5000-5500 in order to rip past someone or just accelerate insanely fast up to triple digit speeds.
In other words, no rational reason at all.

What I can't understand is how someone could 'think' they are taking the extra time to 'rev match', yet be so hasty as to throw it in 2nd by accident.
No idea how one pulls that off, or why anybody would do something that quadruples shift time to rev match on a synchronized transmission where you wouldn't even know if you did it right anyway. . . . .because you know. . . .it's SYNCHRONIZED!
While u make a point about the need to quickly shift 6>4 (no rational reason besides weeeeee), I'm a bit confused on why you wouldn't match engine speeds even with a synchronized transmission. Obviously all modern manual transmissions are synchronized, thus the (boneheaded) ability to put the car in second gear while doing 60+. My understanding is that if it was not synchronized, instead of going into 2nd I would be greeted by the horrid sound of metal teeth gnashing (correct me if I'm wrong). I match engine speeds primarily to allow for super smooth downshifts and to greatly limit slip on the clutch plate (as a means to reduce the normal wear and tear). Is this not a reasonable rational for rev matching?
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Old 07-12-2016, 01:52 PM   #22
bdubblu
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Quote:
Originally Posted by rtv900 View Post
In other words, no rational reason at all.
Really?
What about the wooing of a woman?
That moment where you lock eyes with her... there's that undeniable connection...
What's the only thing that can take those emotions to the next level?

A well placed downshift... THAT'S WHAT!




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Old 07-12-2016, 02:35 PM   #23
JordanOfGilead
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Quote:
Originally Posted by rtv900 View Post
The circumstances would be somebody thinking they need to launch the rpm's up to 5000-5500 in order to rip past someone or just accelerate insanely fast up to triple digit speeds.
In other words, no rational reason at all.

What I can't understand is how someone could 'think' they are taking the extra time to 'rev match', yet be so hasty as to throw it in 2nd by accident.
No idea how one pulls that off, or why anybody would do something that quadruples shift time to rev match on a synchronized transmission where you wouldn't even know if you did it right anyway. . . . .because you know. . . .it's SYNCHRONIZED!
Because rev-matching on a downshift reduces wear on the clutch? What do you do, just drop the shifter and dump the clutch? That's really hard on your drivetrain. A quick throttle blip will get you to close enough revs that you save a lot of wear and tear on your clutch and avoid a significant shock throughout the drivetrain. Rev-matching is good for a car, synchro'd or not.
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Old 07-13-2016, 06:23 AM   #24
rtv900
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Originally Posted by JordanOfGilead View Post
Because rev-matching on a downshift reduces wear on the clutch? What do you do, just drop the shifter and dump the clutch? That's really hard on your drivetrain. A quick throttle blip will get you to close enough revs that you save a lot of wear and tear on your clutch and avoid a significant shock throughout the drivetrain. Rev-matching is good for a car, synchro'd or not.
uhhh yes I do just downshift and 'dump the clutch.'
Not sure that's what I'd call a clutch dump but I suppose.

If I'm downshifting for acceleration I'll phase in the throttle while letting out the clutch which engages it with almost no slip if it's done right.
If I'm downshifting to come to a stop I just "dump it", which slips a tiny bit and doesn't make a lick of difference, or at least since I did that on my last car for 10 years and 280k miles on the original clutch I'm assuming it was ok.
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Old 07-13-2016, 02:37 PM   #25
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Rev matching does not take that much time at all once you get used to it. Also, synchros do nothing to match the engine speed to the transmission speed...Also, giving a throttle while letting out the clutch is usually hard on a clutch, especially compared to rev matching before letting out the clutch. It's easy for the engine to rev up when there is no load on it. If you are giving it gas, you are putting a load on the engine and the clutch will take more abuse trying to match the engine/transmission speed.

There are simple calculators to determine engine speed. For a 2015+ WRX, 70 MPH in 2nd gear is 7400 RPM. 60 MPH is 6400 RPM. There is very little chance that an engine blows if accidentally brought to 7400 RPM. And, if there was some valve float or something and a valve hit a piston, you would no right away. I don't think the transmission will have any issues at that speed, too. If the car is fine now, I would not worry about it. Just be more careful next time.
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