THE INFAMOUS THUMP THREAD
06-28-2007, 07:41 AM
#11
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Originally Posted by SenderGreen,Jun 28 2007, 09:55 AM
Sounds like something in the transmission spins even when the car is at idle, or perhaps takes a few seconds to spin down after coasting to a stop. Maybe when first gear is engaged it brings whatever is rotating to an abrupt stop causing the sensation. Just guessing, I have no idea
thats exactly what is happening, and its completely normal. just hold the clutch in for a couple seconds before throwing it into first, or just put it into first softly/slowly. i had this on my old 03, and also on my 06.
06-28-2007, 07:54 AM
#12
This was explained a while back. When you shift into first gear, you are engaging the layshaft. The thump you feel is the layshaft going from a dead stop to the rpm of the engine. This is normal, and is not a problem.
06-28-2007, 08:38 AM
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MY02 does the same thing. My friends 06 Mazda RX-8 does the same thing. This is how u tell its normal. come to a stop on a small hill, and put it in neutral, then put it in first. U feel the bump. then, keeping your foot on the brake. put it into neutral again, and then put it into first. you DONT feel the bump. now roll a bit and do the same thing, and put it into neutral, then into first. u feel the bump again. its perfectly normal, its the play between the gears on the input shaft and 1st gear in the trans. there is going to be play in the gear, and when u roll to a stop. ur never perfectly aligning the gears. its ok. ive had my trans rebuilt under waranty for the "1st & 2nd gear grind". and mine still does the BUMP. its perfectly normal there is nothing wrong
06-28-2007, 05:25 PM
#16
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Originally Posted by fit4897,Jun 28 2007, 11:38 AM
MY02 does the same thing. My friends 06 Mazda RX-8 does the same thing. This is how u tell its normal. come to a stop on a small hill, and put it in neutral, then put it in first. U feel the bump. then, keeping your foot on the brake. put it into neutral again, and then put it into first. you DONT feel the bump. now roll a bit and do the same thing, and put it into neutral, then into first. u feel the bump again. its perfectly normal, its the play between the gears on the input shaft and 1st gear in the trans. there is going to be play in the gear, and when u roll to a stop. ur never perfectly aligning the gears. its ok. ive had my trans rebuilt under waranty for the "1st & 2nd gear grind". and mine still does the BUMP. its perfectly normal there is nothing wrong
even in nuetral, there are plenty of 'things' still spinning in the tranny due to its connection to the engine. when you quickly put the car into first gear...the 'thump' noise is from everything thats been turning coming to a complete stop due to its connection to the prop shaft, then the diff, then the axles, then to the wheels, which are not moving.
06-28-2007, 07:30 PM
#17
Anybody who knows what a "layshaft" is probably has the correct answer. 
06-28-2007, 07:45 PM
#18
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hey everyone - happy to see there is intrest in this thread and the thump is at least common enough to inspire conversation: SenderGreen, other threads about this subject are in line with your suggestion. really great insight! i took the car for a drive today and found i had a lot of trouble simulating the thump. i made a point to shift quickly into 1st after depressing the clutch, and i still couldn't force the car to thump. it's ironic that you can't make problems happen when trying to understand them, they just happen when it's not helpful. sucks. the posts coming are great. more would be great too, especially any tech savvy posts that descripe in detail what physically happens to cause the thump. thanks everyone.
06-28-2007, 11:02 PM
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I love when people who have never experienced something themselves tell someone else they are wrong and proclaim that they know exactly what is going on. 
I noticed the thump as soon as I bought my 05. It is more prominent when the car is cold, especially when I just start it and haven't moved yet. Holding the clutch in longer does not help. I have held the clutch in and put it in and out of gear several times without releasing the clutch, it thumps every time and the car moves forward a fraction. It has nothing to do with going into gear too soon or driving habits.
I don't have any idea what a layshaft is, nor do I profess to know exactly what makes it happen. But, unlike others here who have no idea what they are talking about, I won't tell someone else they are "wrong!" and go on to provide an answer I pulled out of my ass.
I noticed the thump as soon as I bought my 05. It is more prominent when the car is cold, especially when I just start it and haven't moved yet. Holding the clutch in longer does not help. I have held the clutch in and put it in and out of gear several times without releasing the clutch, it thumps every time and the car moves forward a fraction. It has nothing to do with going into gear too soon or driving habits.
I don't have any idea what a layshaft is, nor do I profess to know exactly what makes it happen. But, unlike others here who have no idea what they are talking about, I won't tell someone else they are "wrong!" and go on to provide an answer I pulled out of my ass.
06-28-2007, 11:18 PM
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Originally Posted by FISH22,Jun 28 2007, 08:25 PM
even in nuetral, there are plenty of 'things' still spinning in the tranny due to its connection to the engine. when you quickly put the car into first gear...the 'thump' noise is from everything thats been turning coming to a complete stop due to its connection to the prop shaft, then the diff, then the axles, then to the wheels, which are not moving.
A "thump" that is hard enough to move the car can't be good for the gearbox.
I've never seen it when a car is shifted properly, and would never consider it normal.
I do know what a layshaft is, but that doesn't help me know what these guys are hearing and feeling, and I'm not even sure they're all describing the same thing.
