# Weird clunk noise when i shift into REVERSE on start up. Help?



## dddrew. (Jul 28, 2010)

Is it normal for a car to start up as a cold start every time you turn on your car? Every time i start my car (even when its warm outside, and i've already driven it to work and back), my car will idle at 2500 RPMs. Even if i push my clutch in all the way it still keeps idleing. It takes, what feels really long, about 30 seconds until it starts dropping (even if the clutch pedal is pushed down or not). While it's idleing at that high, if i go to push down the clutch pedal and move the transmission into reverse, i'll get this loud clunking noise. It's a 5speed tranny with one of those shifters that you push down and move into 1st gear position to get into reverse, so it feels like im putting a lot of force in it. I also notice this when i start up my car and drive for 3 feet (in first gear obviously), the gear will catch really weird, and the idles don't lower for a couple of seconds. But the thing im most worried about is when i go into reverse. I don't think im doing anything wrong, it just doesn't seem normal for a car to idle that long and not drop RPMs when i push the clutch in and move it into a gear... 

When i sit for 30 seconds and let the RPMs lower, it shifts into reverse fine. When i go driving somewhere and decide to reverse somewhere, it shifts fine. Just whenever i start the car it wont shift correctly. 

edit: I have a mkv 2007 jetta 2.5l 5 speed manual tranny.


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## edb4 (Mar 4, 2009)

The "clunk" is just the sound of your non-synchroed reverse gear meshing up. This is normal. 

The high idle doesn't sound right, however.


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## dddrew. (Jul 28, 2010)

edb4 said:


> The "clunk" is just the sound of your non-synchroed reverse gear meshing up. This is normal.
> 
> The high idle doesn't sound right, however.


 Wait, what? So it's normal for the transmission to make the loud clunk/bang noise and the car shake before i even let go of the clutch to start moving?


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## edb4 (Mar 4, 2009)

Short answer: Yes. Normal. 

Long answer: When you first start the car, your high idle will cause your transmission input shaft to spin at the same speed as the engine. When you disengage the clutch and attempt to shift into reverse, that input shaft is still revolving quite quickly, while the output shaft is not moving at all, since the wheels are not moving. Once you push the gear selector into the reverse position, the teeth of the gear must align with the selector's collar in order to engage. In all forward gears, you have synchros that will match the collar speed to the gear speed in order to ensure that the gear teeth are aligned and do not grind. In reverse, this synchro is absent, so the "crunch" you hear is the teeth being forced to align. The reason why you might not hear this noise often is if you try to shift into reverse while engine speed is at idle, it's much easier for the teeth to catch without grind. However, since you're trying to engage reverse while engine speed is higher, you'll create a more noticeable grind. 

If that doesn't make sense, pictures: http://www.howstuffworks.com/transmission.htm 

Also, the light jump you might feel when you engage reverse in such a situation is normal. Basically, even though the engine is not connected to the transmission during the shift, parts of the transmission are still in motion. When you try to connect the in-motion parts of the transmission to the parts that are stopped (connected to the wheels), that sudden loss of momentum has to go somewhere. It will usually result in very minor movement. 

TL;DR: Your reverse gear is fine. Worry about that high idle.


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## dddrew. (Jul 28, 2010)

edb4 said:


> Short answer: Yes. Normal.
> 
> Long answer: When you first start the car, your high idle will cause your transmission input shaft to spin at the same speed as the engine. When you disengage the clutch and attempt to shift into reverse, that input shaft is still revolving quite quickly, while the output shaft is not moving at all, since the wheels are not moving. Once you push the gear selector into the reverse position, the teeth of the gear must align with the selector's collar in order to engage. In all forward gears, you have synchros that will match the collar speed to the gear speed in order to ensure that the gear teeth are aligned and do not grind. In reverse, this synchro is absent, so the "crunch" you hear is the teeth being forced to align. The reason why you might not hear this noise often is if you try to shift into reverse while engine speed is at idle, it's much easier for the teeth to catch without grind. However, since you're trying to engage reverse while engine speed is higher, you'll create a more noticeable grind.
> 
> ...


 Thanks, i must have exaggerated the high idle though, i just took another look and it idled around 1800 RPM, it just felt like it was a lot higher. I understand how it's making the noise, but why? Shouldn't there be some type of counter to avoid this problem? Im assuming over time this is bad for the transmission if i keep doing this? Is it normal to always turn a car on and forcefully wait 20-30 seconds until you can put it into reverse? Or are you supposed to live with the noise and don't mind it? It scares the crap out of me when i do it. 

All the other manual cars i driven have never had this type of problem. It just didn't seem normal to me.


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## Tubaplaya (Mar 29, 2008)

dddrew. said:


> Thanks, i must have exaggerated the high idle though, i just took another look and it idled around 1800 RPM, it just felt like it was a lot higher. I understand how it's making the noise, but why? Shouldn't there be some type of counter to avoid this problem? Im assuming over time this is bad for the transmission if i keep doing this? Is it normal to always turn a car on and forcefully wait 20-30 seconds until you can put it into reverse? Or are you supposed to live with the noise and don't mind it? It scares the crap out of me when i do it.
> 
> All the other manual cars i driven have never had this type of problem. It just didn't seem normal to me.


 The reverse thing is normal. I drive an 07 rabbit 5spd and it does the same thing. I found out that if you put the shifter into first and THEN into reverse it doesn't grind anymore. Do this obviously while the car is warming up. I like to let my car warm up for the 20 secs or so before I drive it. In all my previous vehicles I never did and it was weird but I got used to it over time.


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## edb4 (Mar 4, 2009)

dddrew. said:


> I understand how it's making the noise, but why? Shouldn't there be some type of counter to avoid this problem? Im assuming over time this is bad for the transmission if i keep doing this?
> 
> All the other manual cars i driven have never had this type of problem. It just didn't seem normal to me.


 Sure, you can avoid the grind by either easing the shifter into reverse much slower, tag a different gear first (punch first gear, then move into reverse without engaging the clutch), or wait for your idle to drop to a reasonable level. No, you're not damaging your transmission because of this grind. You'd do more damage to your transmission by dumping the clutch at full throttle just once than you would grinding into reverse 100 times. If you ever managed to break a dogtooth because of shifting into reverse, you'd probably be the first person in automotive history to manage to pull it off (exaggeration, but still pretty solid.) 



dddrew. said:


> Is it normal to always turn a car on and forcefully wait 20-30 seconds until you can put it into reverse? Or are you supposed to live with the noise and don't mind it? It scares the crap out of me when i do it.


 When you first fire up your car from cold, you should let the idle drop down to normal before driving off. There's a reason why the car starts up with a high idle. However, the high idle when the car is already warm sounds like a problem. 1800rpm is to be expected from a cold start, but when already warm, you should drop from the initial 1500-1800rpm startup range to about 800rpm in less than 5 seconds. I don't know what the problem could be, to be honest. Others from the 'tex should chime in here. Do you have any mods? My first guess would to be to make sure your temp sensors are working properly.


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## rags2riches (Jan 2, 2010)

I think dude may be exaggerating the high idle. My car takes about 20 or so seconds to come down from high idle after a cold start. He never really said it happens after the car is warm. He said even after he drives to work and back. Well, was he at work for eight hours because that is certainly enough time for the engine to cool down and have to cold start again. Please elaborate on this. Does it do it every single time you start it even after it has warmed up and remains to be so. If so, it could be anything from you MAF sensor to you throttle position sensor or even cam position sensor. Does it idle smoothly after it warms up and the revs drop? OR does it sound kind of rough like maybe it is out of time or something. He could have a worn timing chain guide and a stretched timing chain causing his engine to have bad cam timing and bad valve timing which might explain the long time it takes the engine to calm down after cold start. I would try to explain the situation better so as to get a more accurate diagnoses.


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## dddrew. (Jul 28, 2010)

I do not have any performance mods done to my car. Like i said, it idles around 1800 RPM for quite a while. Im for sure it's more than 5 seconds, probably 20 seconds to be on the safe side. I just turned on my car today to move it for somebody and they were looking at me like "wtf?, why aren't you backing up?" after i turned on the car. Had to let it sit for a while before the RPMs finally dropped. Even after waiting a while i said **** it and put it in reverse, got the same crunch / car shake.

I mean, if i drive somewhere to pick up something from the store really quick, it'll start up fine on the way back (no long idle). But if it sits for more than an hour it feels like a cold start or atleast the RPMs are just chilln up at 1800a while lol... I wouldn't be making such a fuss about it if it wasnt true.


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## edb4 (Mar 4, 2009)

dddrew. said:


> Im for sure it's more than 5 seconds, probably 20 seconds to be on the safe side.


Get a stopwatch.



dddrew. said:


> Even after waiting a while i said **** it and put it in reverse, got the same crunch / car shake.


 A guy goes to the doctor and says "Hey doc! It's hurts when I do _this_!" The doctor looks at him and says "Well, don't do that anymore!"



dddrew. said:


> I mean, if i drive somewhere to pick up something from the store really quick, it'll start up fine on the way back (no long idle). But if it sits for more than an hour it feels like a cold start...


Start expecting a cold-start ignition routine from your car when the car is cold.

I see no issues here.:thumbup:


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## Gunbunny08 (Nov 13, 2008)

Yeah it is defintely normal. i drive an 08 rabbit and it does the same thing and its always more noticable in the morning. but i also noticed that it happens much more often and its much louder on hills. even slightly slanted driveways like mine.


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## vwluger22 (Jan 25, 2005)

Tubaplaya said:


> The reverse thing is normal. I drive an 07 rabbit 5spd and it does the same thing. I found out that if you put the shifter into first and THEN into reverse it doesn't grind anymore.


 x2 on this almost all manual VW trannys you got to do this. :thumbup:


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## OcDub4Life (Apr 13, 2009)

It's normal to have it idle high on a cold start up. It's an emissions thing. On cold starts the ecu holds the exhaust valve open for longer in order to warm up the catalytic converter faster. Cats only work when theyre hot. Its not a warm up period. You shouldn't wait for it to stop, it's there just in case you decide to do so, but if you start driving it it will warm up faster. There is no need for you to worry about it. 

Your tranny is fine as well, happens to me all the time and like the other poster said if you don't want it to "clunk" when going in reverse put the car in reverse then start the car. That way you are in gear and your snychros are lined up with the output shaft. Just don't forget that you are in gear and try to walk away from the car and you pop the clutch. 

I don't even wait for the idle to die down in the morning, I start mine up, put it in gear and let the clutch out without even giving it gas. It's my lazy way to start my morning drive. 

Also don't forget you could have checked the DIY for the explanation for the high idle 

http://forums.vwvortex.com/showthread.php?1992178 Explanation at the bottom 

http://forums.vwvortex.com/showthread.php?3218553-**2.5L-Inline-5-FAQ-and-DIY** Fourth post down


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