[e90_enjoyer]

Hi there,

Trying to diag some drivetrain slop/slack on my 330i. Car is a 2006 with 135k miles.

Usually it will occur when I shift and don't get the rev match perfect and let the clutch out too quickly (i.e. low speed 1-2 shifts), and also in higher gears on the highway. If I step on it in 6th, then let off, and quickly get on it again, you'll feel it.

It feels like a dull thunk/thud under the driver's seat around the trans area almost. It isn't audible really, it's just like a driveline shock.

I recently did my engine mounts + the trans mounts. I did not notice any sheared bolts on the engine mount brackets, but even if that was my issue I feel like it would be much louder/violent. It feels more like a bad bushing or something as it's dull/rubbery feeling.

I've read it could be the guibo, but I looked at the front one and it looked fine. I have not looked at the rear one nor the CSB, it's on my list for next time I'm under the car. I don't get any driveline vibrations whatsoever, otherwise I'd just do both of them. Last shop I took it to told me to keep an eye on it as it showed some minor cracking but I'm not sure which guibo they were referring to.

I also read it could just be the flywheel? I've never driven a car with a DMFW. Mine does exhibit the idle rattle that seems to be common but otherwise no other symptoms.

Any other tips on what else to look for? I'm doing front control arms soon, I'll check the csb and other guibo. Just would rather not replace something that's fine lol. Thanks in advance!

[jacbo]

Look at the diff bushings especially the big rear bush. Try and move the diff and you'll see if it's split. Mine was shot and had very similar symptoms to yours.

I did my guibos and centre support at the same time. I noticed cracking as well but the real test is once you get the guibos off and compare to brand new parts. when i slid a screwdriver into the bolt hole and levered it, the cracks would open up even further so these were super loose compared to new guibos.

No more clunking sounds... I replaced all this at around 148k miles but my diff bush was split since around 130k but it took me two attempts and extra tools to eventually get it out the subframe.

[Maxmax73]

E30 or E46 M3 transmission mounts help a bit, if you feel like things are moving around too much.

[Suvorovo]

330xi 6 Speed. Have the same clunk issue when not properly rev matching on first and second gears. No issues or slipping in higher gears. Guibos and rear diff bushings are fine. I also replaced my motor mounts around 1k miles ago when I noticed a broken off engine bracket bolt. If the center support bearing was bad, you'd have horrible noises all the time. I found that reducing the speed at which you depress the clutch reduces the driveline backlash.

I think it's just a symptom of a worn DMFW. I'm at 124k miles with original clutch and you're at 135k. It sounds like it's about time to replace.

I'll be doing clutch/DMFW once I finish refreshing the engine with new DISA Valves and PCV. (PCV is fine, you can test yours by opening the engine oil cap while the car is running and checking for massive suction. Good PCV makes a fast blubblubblub sound when running)

Jacbo, what special tools did you need other than bushing puller/press?

[whyzee125]

There are a lot of parts that can and likely will be worn at that age. Subframe bushings, diff bushings, giubo, CSB, all rear suspension arms. Even your flywheel can cause this if it's original

[e90_enjoyer]

Originally Posted by Suvorovo

330xi 6 Speed. Have the same clunk issue when not properly rev matching on first and second gears. No issues or slipping in higher gears. Guibos and rear diff bushings are fine. I also replaced my motor mounts around 1k miles ago when I noticed a broken off engine bracket bolt. If the center support bearing was bad, you'd have horrible noises all the time. I found that reducing the speed at which you depress the clutch reduces the driveline backlash.

I think it's just a symptom of a worn DMFW. I'm at 124k miles with original clutch and you're at 135k. It sounds like it's about time to replace.

I'll be doing clutch/DMFW once I finish refreshing the engine with new DISA Valves and PCV. (PCV is fine, you can test yours by opening the engine oil cap while the car is running and checking for massive suction. Good PCV makes a fast blubblubblub sound when running)

Jacbo, what special tools did you need other than bushing puller/press?

I still haven't gotten under the car, but from what I've read you can use the $70 bmw bushing puller set from Amazon and a 3 inch PVC pipe + a small 2x4 to yank the big diff bushing out. Vehicular DIY did a video:

I agree it could be the DMFW - but I'd reallllly hope it isn't, that's a big job 😭. I'll check the diff bushings out soon. I have a GoPro I may stick under the car and see if i can get a shot of the movement

[jacbo]

yeh that video is a good guide. i got a more comprehensive puller set so didn't need to get creative on bigger bushing using PVC pipe etc. Mine was also badly seized in (UK car) so had to get blow torch on to get it out.

For front diff bushings i would recommend a ratcheting 18mm spanner. hard to get access with a ratchet wrench so i was struggling with a standard 18mm spanner. Pretty easy job all in all just quite time consuming