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Old 01-31-2018, 01:21 PM   #1
FLTFOUR
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Default 6MT “Thud” when engaging 1st Gear

On my commute to work today I noticed a “thud” a few times when engaging 1st gear from a stop light.

This only occurs when: clutch is out, light turn turns green, clutch in, put into first gear. It seems like I can even feel it in the floor and clutch pedal when it happens but idk if that’s just me overthinking it.

What’s going on? This car is brand new...barely 2,000 miles on it!
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Old 01-31-2018, 01:36 PM   #2
inthenameofweez
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Hmmmm. Bushing for trans or diff mounting? The driveline could be shifting during engagement...
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Old 01-31-2018, 01:58 PM   #3
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Quote:
Originally Posted by FLTFOUR View Post
On my commute to work today I noticed a “thud” a few times when engaging 1st gear from a stop light.

This only occurs when: clutch is out, light turn turns green, clutch in, put into first gear. It seems like I can even feel it in the floor and clutch pedal when it happens but idk if that’s just me overthinking it.

What’s going on? This car is brand new...barely 2,000 miles on it!
Warranty! You have one. Take it to the Dealer.
Could be anything at this point except maybe ... oh, never mind
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Old 01-31-2018, 03:26 PM   #4
Infinite0180
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Its normal. Check around here a bit more. Somebody explains exactly what happens and why. I cant remember the specifics though
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Old 01-31-2018, 10:53 PM   #5
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I’ve read that when you depress the clutch and slam into gear without letting the transmission catch its breath you get a resulting thud.

From what I gather it’s due to the fact that the input shaft is still rotating or slowing down from when it was at idle speed. And then the action of selecting a gear halts that motion resulting in a thud.

I actually found that if you depress the clutch and give it a second before selecting the gear then you get no abnormal thud/cluck/ or whatever you want to call it.
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Old 02-01-2018, 10:24 AM   #6
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OK, so now you are telling us that you are slamming gears, but couldn't understand why your transmission was going "THUD!"

Good job.
I see a new transmission in your near future
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Old 02-01-2018, 01:03 PM   #7
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Quote:
Originally Posted by Samurai Jack View Post
OK, so now you are telling us that you are slamming gears, but couldn't understand why your transmission was going "THUD!"



Good job.

I see a new transmission in your near future


Don’t hang on these words so much pal. It wasn’t meant literally. By slamming I mean throwing it in gear without giving it a second to catch up. And this is only from neutral to first while at a stop. Don’t get too EXCITED.
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Old 02-01-2018, 01:17 PM   #8
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Quote:
Originally Posted by FLTFOUR View Post
Don’t hang on these words so much pal. It wasn’t meant literally. By slamming I mean throwing it in gear without giving it a second to catch up. And this is only from neutral to first while at a stop. Don’t get too EXCITED.
You should kill your 1st gear synchro very soon.
Good job
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Old 02-01-2018, 01:31 PM   #9
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Originally Posted by Samurai Jack View Post
You should kill your 1st gear synchro very soon.

Good job


That’s probably the most productive advice you’ve given and you probably didn’t intend it either.

A better way to say this would be: go slow and let you synchros do their job.
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Old 02-01-2018, 07:09 PM   #10
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Originally Posted by FLTFOUR View Post
That’s probably the most productive advice you’ve given and you probably didn’t intend it either.

A better way to say this would be: go slow and let you synchros do their job.
You spend enough time here, you’ll learn it’s not worth your time acknowledging some people. This is why I try to not get involved with the community too much.
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Old 02-02-2018, 06:06 PM   #11
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If you're starting from neutral and depress the clutch, you'll ideally want to snap it into gear pretty quick - if you wait too long, you might end up having the gears come to a rest in a position where you cannot engage the fork. You're not going to damage a think by shifting from neutral quickly.

You should hear a click, but not a thud. Since these terms are pretty subjective, go listen to someone driving a doxbox transmission on YouTube - if you aren't getting a thud that loud, you probably have no issues.

When shifting gears in motion, you will be forcing your synchros to work harder by shifting quickly. That being said, even if you're slamming the gears as fast as possible, modern transmissions were designed to shift quickly AND last 150k miles or more... that's why they don't even put an oil filler on a lot of new ones. You won't be doing anywhere near the amount of wear as if you skipped gears (i.e. a 1st to 3rd/4th/5th up-shift) or downshift regularly without rev matching. These are the things that cause synchro wear/damage as they are dealing with a much larger speed mismatch between components.
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Old 02-03-2018, 09:26 AM   #12
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Quote:
Originally Posted by fltfour
I’ve read that when you depress the clutch and slam into gear without letting the transmission catch its breath you get a resulting thud.
Quote:
Originally Posted by dankor View Post
You spend enough time here, you’ll learn it’s not worth your time acknowledging some people. This is why I try to not get involved with the community too much.
He openly admitted he is slamming gears. Pretty clear there, and now he is complaining, and so are you?

Slamming gears it not healthy for the transmission, especially if you are expecting a long life out of it. Some people don't care about that, others do.
Forcing the transmission into a gear when it's not designed to do that gear shift at that point in time is also bad for the transmission.

Last edited by Samurai Jack; 02-04-2018 at 12:00 PM.
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Old 02-03-2018, 06:38 PM   #13
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I've been daily-launching and flat foot shifting an 04 STi 6MT for 100k miles. Just did a rebuild at 110k with all new gears/synchros/bearings and it was immaculate inside.

Only thing that was worn was a noisy rear transfer case bearing.

I was impressed =)
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Old 02-04-2018, 08:01 AM   #14
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Those are things that are rough on the clutch, but not so much the transmission.
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Old 02-08-2018, 11:17 PM   #15
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Quote:
Originally Posted by mrsaturn7085 View Post
Those are things that are rough on the clutch, but not so much the transmission.
Well, that's because it's a well-built transmission. Not sure I'd be daily-launching the 5MT at 4500rpm like I do in the 6MT.

My axles are really the weak point.
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Old 02-22-2018, 05:32 PM   #16
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Originally Posted by dankor View Post
You spend enough time here, you’ll learn it’s not worth your time acknowledging some people. This is why I try to not get involved with the community too much.
Yeah I've come to realize that this community is crap based on the condescending attitude you encounter 90% of the time. These people seem to grow fuzz on their kiwi's real quick when they're behind a computer screen.

Quote:
Originally Posted by mrsaturn7085 View Post
If you're starting from neutral and depress the clutch, you'll ideally want to snap it into gear pretty quick - if you wait too long, you might end up having the gears come to a rest in a position where you cannot engage the fork. You're not going to damage a think by shifting from neutral quickly.

You should hear a click, but not a thud. Since these terms are pretty subjective, go listen to someone driving a doxbox transmission on YouTube - if you aren't getting a thud that loud, you probably have no issues.

When shifting gears in motion, you will be forcing your synchros to work harder by shifting quickly. That being said, even if you're slamming the gears as fast as possible, modern transmissions were designed to shift quickly AND last 150k miles or more... that's why they don't even put an oil filler on a lot of new ones. You won't be doing anywhere near the amount of wear as if you skipped gears (i.e. a 1st to 3rd/4th/5th up-shift) or downshift regularly without rev matching. These are the things that cause synchro wear/damage as they are dealing with a much larger speed mismatch between components.
Thank you for your response. I was looking for somebody to break this down exactly like you have. I'm new to manual transmissions and especially to our quirky little Subaru 6 speed therefore naturally I have some questions and some doubts about normal operation.

I have not experienced the "thud" since the original days of the post. Quite honestly it only happened a few times and it was a new event that never occurred before therefore I was wondering if anyone else has experienced this. I get the "click" when it engages and thats it, no "thud".

At this point the car is perfect and I love every moment of driving it. There is nothing better than bonding with the car while performing a perfectly executed downshift and buttery smooth shift changes. Every drive is fun and I get to perfect my techniques.

Last edited by FLTFOUR; 02-22-2018 at 05:38 PM.
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Old 02-23-2018, 01:11 PM   #17
mrsaturn7085
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Happy to help - not to sound high and mighty here, but I'm probably one of maybe three members on NASIOC to have rebuilt the 6MT in my garage (3 times in 6 months, no less - and through no fault of my own) so I'm pretty familiar with the ins and outs.

It is a very stout transmission and by design, even with internal damage it will likely make a LOT of noise long before it grenades itself. This is really helpful as you can pit the car and pull the transmission before any further damage occurs. The 2000-2007 6MT is probably one of the best designed transmissions I've ever opened up - it was designed from the ground-up for our cars and engine output - aside from a few select specialty tools, it's dead-simple to work on.
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