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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sun, Jul-21-2019, 08:22:55 PM   #1
Cubieman
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Default Thump sound when putting car in gear

Every so often when I put my car into 1st gear when ready to depart from a stoplight I hear a thump from the trunk area. It's not an extremely loud sound, but it's enough to take notice. Someone told me it's my trunk floor flexing...huh?
I have a 2004 and subframe has been reinforced.

I've also heard this noise when shifting into higher gears on occasion but it seems to be most pronounced when putting it into 1st. Doesn't happen all the time so its kind an intermittent deal. Seems to happen more often after the car has been driven hard.
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Old Sun, Jul-21-2019, 08:31:41 PM   #2
Drewster
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Default Re: Thump sound when putting car in gear

At a stop light? Every manual car does this.

Essentially, when you're sitting at a light in neutral, foot off the clutch, it means the crank, flywheel, clutch, and input shaft are all spinning at the same speed. When you clutch in and pop the car into first, the inertia of the still-spinning clutch and input shaft makes the trans and driveshaft go "thunk" as the synchros dissipate that energy and bring everything to the same speed (0).

If you're saying it happens as you let off the clutch and apply power, you likely have a trashed bushing somewhere either on the diff/ driveshaft/ etc. and should check it out.
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Old Sun, Jul-21-2019, 08:45:53 PM   #3
Cubieman
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Default Re: Thump sound when putting car in gear

It's just when I put my foot on the clutch and put it into 1st gear. Just strange to me that it's an intermittent deal.
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Old Sun, Jul-21-2019, 08:52:02 PM   #4
cgeromi
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Default Re: Thump sound when putting car in gear

Little trick I do with all manual transmissions is from a dead stop I cycle into 2nd gear then into first. Definitely relieves any stress compared to just putting her into 1st. I've owned many many 5 speed cars and all have made it past 250k miles with no synchro issues.

Also if first is a little wonky I'd dump the gear oil and go with some fresh. Never hurts.

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Old Sun, Jul-21-2019, 09:35:59 PM   #5
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Default Re: Thump sound when putting car in gear

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Originally Posted by Cubieman View Post
It's just when I put my foot on the clutch and put it into 1st gear. Just strange to me that it's an intermittent deal.
It probably corresponds to how much of a hurry you're in, but it might not hurt to bleed the clutch slave if you've never done it (with the assumption that the clutch isn't 100% releasing)
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Old Sun, Jul-21-2019, 11:19:31 PM   #6
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Default Re: Thump sound when putting car in gear

Another "M-Clunk" sighting.
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Old Mon, Jul-22-2019, 12:18:36 AM   #7
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Default Re: Thump sound when putting car in gear

Good thing you dont own an smg lol. You’d be terrified!


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Old Mon, Jul-22-2019, 01:27:56 AM   #8
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Default Re: Thump sound when putting car in gear

I think 1st gear is straight cut gear not synro. Same with reverse. Someone correct me if im wrong. What you hearing is normal.
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Old Mon, Jul-22-2019, 02:28:13 AM   #9
Cubieman
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Default Re: Thump sound when putting car in gear

This may not be best practice, but many times I will downshift from 4th 3rd when comming to a stop then just put it into neutral and coast on up to the light. I only do this when I know its going to a be a long light etc.
It's always been put into my head, brake pads are cheaper than clutches...
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Old Mon, Jul-22-2019, 02:38:08 AM   #10
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Default Re: Thump sound when putting car in gear

Quote:
Originally Posted by cgeromi View Post
Little trick I do with all manual transmissions is from a dead stop I cycle into 2nd gear then into first. Definitely relieves any stress compared to just putting her into 1st.
I do this as well when doing lots of stop-and-start through stop signs etc. The trans doesn't want to go directly into first because of the clutch inertia Drewster mentioned.

Quote:
Originally Posted by Cubieman View Post
Every so often when I put my car into 1st gear when ready to depart from a stoplight I hear a thump from the trunk area.
Check your diff bushings. Mine are shot and every time I take off too quickly or change speed (slowing down in gear) it clunks really loudly. Currently not driving it until I get the time to pull the diff and replace them.
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If you wanna make REAL donuts, run Crisco in your diff.
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Discussing Thump sound when putting car in gear in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)