thud,thump sound from drivetrain?help!

[fun2k]

Just recently i bought a bmw 1m ,was fortunate enough or rather very lucky to have stumbled upon one standing at the dealer,been searching for it since very very long time.

I will skip the review for later,im still in the break in period ,done about 500km.
The problem is when im on the motorway above 80km/h or above 3rd gear and if i let off/on the gas abruptly there is a knock like sound(not so loud that the passenger cant actually hear the sound but the driver can feel it coming from the back for the car).

Basically if youre loading or unloading the drivetrain at above 80km/h it feels like there is some play in the driveshaft or backlash?

should i take it to the dealer? or is this normal for it to have a little backlash?
thx

[eeghie]

Originally Posted by fun2k

Just recently i bought a bmw 1m ,was fortunate enough or rather very lucky to have stumbled upon one standing at the dealer,been searching for it since very very long time.

I will skip the review for later,im still in the break in period ,done about 500km.
The problem is when im on the motorway above 80km/h or above 3rd gear and if i let off/on the gas abruptly there is a knock like sound(not so loud that the passenger cant actually hear the sound but the driver can feel it coming from the back for the car).

Basically if youre loading or unloading the drivetrain at above 80km/h it feels like there is some play in the driveshaft or backlash?

should i take it to the dealer? or is this normal for it to have a little backlash?
thx

Congrats and welcome!

During break in it's advisable to go of the gas not too abruptly as at such instances you are wearing in the alternate flanks of your differential cogs. Some backlash yeah, but obviously can't tell about yours. If you think there's something wrong, call or see the dealer.

looking forward to that review

[Dan Parker]

As said, take it to the dealer. Your diff may be bad. It will be important that your service advisor or mechanic can duplicate it as that's going to be critical in the case they think it should be replaced.

[MDORPHN]

Originally Posted by Dan Parker

As said, take it to the dealer. Your diff may be bad. It will be important that your service advisor or mechanic can duplicate it as that's going to be critical in the case they think it should be replaced.

Agree.

And if it was an older E46, I would have guessed torn rear subframe.

Neil

[fun2k]

thx for the advise ,i guess il have to take it to the dealer tomorrow.

[fun2k]

Went to the dealer today,said everything is ok and that its normal for manual cars especially M cars to do this.

i would really appreciate it if someone else can also try the following on their 1m and see if they produce similar results... "at about 60-80mph put the car on cruise and then just as you turn it off (through the stalk not brake)you can feel a slight "dhug" coming from the drivetrain".

[miula]

Originally Posted by fun2k

Went to the dealer today,said everything is ok and that its normal for manual cars especially M cars to do this.

i would really appreciate it if someone else can also try the following on their 1m and see if they produce similar results... "at about 60-80mph put the car on cruise and then just as you turn it off (through the stalk not brake)you can feel a slight "dhug" coming from the drivetrain".

Mine does it as well as many others. It also thumps if you abruptly let off the accelerator in 5th/6th gear at 70 - 90 mph. The dealer last year said it was normal and attributed to the dual mass flywheel. There was a lot of discussion about it in the past if you search the forum. It has been posted many times...

[mad4che]

Mine does it too.... didn't notice it until after break-in when I took it on my first real road trip. Kind of annoying... you'd think that this is something that shouldn't be happening in a car of this caliber.

[flzrider]

It has been discussed before and it seems to be normal.

My guess would be that it is caused by the M3 rear diff. The thud can be felt from the rear of the car.

[Maximus_Prime]

Originally Posted by miula

Mine does it as well as many others. It also thumps if you abruptly let off the accelerator in 5th/6th gear at 70 - 90 mph. The dealer last year said it was normal and attributed to the dual mass flywheel. There was a lot of discussion about it in the past if you search the forum. It has been posted many times...

+1. It's just another quirk in our car's personality. I swear, with all the thumps and thuds that come of out the 1M's drivetrain, all my passengers either think that something's broken in my car or that I don't know how to drive it. Of course then I let the beast loose and they all seem to get really quiet

Here are some of the threads miula is referencing:
http://www.1addicts.com/forums/showthread.php?t=589890
http://www.1addicts.com/forums/showthread.php?t=565832

[rapter]

Originally Posted by miula

Mine does it as well as many others. It also thumps if you abruptly let off the accelerator in 5th/6th gear at 70 - 90 mph. The dealer last year said it was normal and attributed to the dual mass flywheel. There was a lot of discussion about it in the past if you search the forum. It has been posted many times...

Normal noises on mine, these thuds happen all the time

[fun2k]

Thankyou so much for everyones input on this,i was so worried that i might be the only one and since im planning to keep the car for a long time(although that usually never plans out ,last car was a 2010 gt3 which i still regret selling) this small thing kept bothering me every few minutes.

i guess they have kept some tolerance in the parts for heat expansion in the joints??

btw the car is amazing, even in second gear with light - medium throttle the car wants to go sideways.

Oh and this forum is amazing! very helpfull and honest feedback. Im glad to be a part of this community.

[rapter]

Originally Posted by fun2k

Thankyou so much for everyones input on this,i was so worried that i might be the only one and since im planning to keep the car for a long time(although that usually never plans out ,last car was a 2010 gt3 which i still regret selling) this small thing kept bothering me every few minutes.

i guess they have kept some tolerance in the parts for heat expansion in the joints??

btw the car is amazing, even in second gear with light - medium throttle the car wants to go sideways.

Oh and this forum is amazing! very helpfull and honest feedback. Im glad to be a part of this community.

What surfaces are you driving on that "light-medium" throttle input makes the car want to drive sideways??? Mine is rather planted at light-medium throttle.

[fun2k]

i guess it was on a slight curved road i might add and one time on a straight road,but it wasnt a perfect road surface(kinda like the one that little shiny surface).this was at 38deg cel outside temp.

im still running in the car so havent really done a lot of hard 2nd gear pulls.

[robgus]

It's even mentioned in the manual of the car.

[fun2k]

actually i didnt get the manual with the car,and when i got it after 1 week from the dealer its mentioned as "clicking" noise instead of "clacking" which is why i was worried.

[TheSt|G]

Yeah, you guys have M clunk, which is a side effect of the M Variable Lock differential. Completely normal.

[fun2k]

Originally Posted by rapter

What surfaces are you driving on that "light-medium" throttle input makes the car want to drive sideways??? Mine is rather planted at light-medium throttle.

Just finished the 1200mile break in. Im happy to report in M mode 50-70% throttle in second gear the car loses traction on all surfaces and this is in hot weather 38-40 deg C and my tyres are practically new.so i guess 1st gear is pretty much useless on this car. The stock power in this car feel way more than i had anticipated, my 135i never lost traction like the 1m in 2nd gear especially on straights. i also feel unlike others have stated there is some turbo lag compared to my 135i(i couldnt detect any lag in that car from any rpm).