Loud thud when going into reverse SMG, strange clutch egements

[BMW_QAS]

You think the solid mounts led to this failure?

100%, Yes. I think they probably began as small stress fractures in the aluminum. From there it was only a matter of time and repeated stress. Those mounts would work better with a steel or titanium crossmember, but not weak cast aluminum.

[Nico]

Before I swapped out to manual my car had semi-similar issues. Took a long time to go into reverse, gear change indicator would blink and the car would not go into gear, only gears selectable were odd gears 1,3,5. As it turns out my car had multiple problems.

The transmission mount crossbar was cracked in two places and the “ears” of the transmission were broken off. Nothing was physically supporting the transmission. Car had aluminum mounts on the engine and trans.

Inside the transmission bellhousing the plastic shift pivot point was broken completely. The shift arm was free floating. The throw out bearing looked original, and had copiously large amounts of sludge and yuck all over it. The clutch disc was worn almost to the rivets.

What I’m trying to say is: You may have multiple issues. Don’t rule anything out until you or a mechanic you trust looks at the system as a whole.

Good luck,

-Steve

Could be, my car has never had an issue engaging any gear after the motor replacement though.

Took it for a drive yesterday, this time when I started it up, waited for the RPMs to drop after being cold and no slamming in reverse. Weird.

[eacmen]

Here is the cross brace. The cracks could not be seen by just looking under the car. The crossbar fell apart when the load on the transmission was removed.

You think the solid mounts led to this failure?

[BMW_QAS]

Here is the cross brace. The cracks could not be seen by just looking under the car. The crossbar fell apart when the load on the transmission was removed.

[BMW_QAS]

Before I swapped out to manual my car had semi-similar issues. Took a long time to go into reverse, gear change indicator would blink and the car would not go into gear, only gears selectable were odd gears 1,3,5. As it turns out my car had multiple problems.

The transmission mount crossbar was cracked in two places and the “ears” of the transmission were broken off. Nothing was physically supporting the transmission. Car had aluminum mounts on the engine and trans.

Inside the transmission bellhousing the plastic shift pivot point was broken completely. The shift arm was free floating. The throw out bearing looked original, and had copiously large amounts of sludge and yuck all over it. The clutch disc was worn almost to the rivets.

What I’m trying to say is: You may have multiple issues. Don’t rule anything out until you or a mechanic you trust looks at the system as a whole.

Good luck,

-Steve

[Nico]

I had a similar loud clunking issue when downshifting at higher RPM and what felt like weird shuttering and chatter at low speed. It turned out the front poly diff bushing extruded itself onto the diff and out of the housing. I just replaced it with the upgraded design from revshift. The car no longer has these issues and drives very solid.

I would suggest two things:
1. Run the smg bleed and adaptation procedures again. I ran mine like 5 times after my relocation lol.
2. Check the front diff bolts and all diff bushings.

Good luck and hopefully this helps!

Thanks

[Johnvu]

I had a similar loud clunking issue when downshifting at higher RPM and what felt like weird shuttering and chatter at low speed. It turned out the front poly diff bushing extruded itself onto the diff and out of the housing. I just replaced it with the upgraded design from revshift. The car no longer has these issues and drives very solid.

I would suggest two things:
1. Run the smg bleed and adaptation procedures again. I ran mine like 5 times after my relocation lol.
2. Check the front diff bolts and all diff bushings.

Good luck and hopefully this helps!

[oceansize]

I'd take it the shop cudzich09 mentioned as I've seen them mentioned a bunch over the years but couldn't think of the name. Much better place to start than a dealer.

[Nico]

How many miles on the car?

170k on the chassis, engine has around 100k. Had to replace the whole engine at 155k, took a shit on me

[oceansize]

Drives fine under power. Have tested out redlining in second and 3rd a couple times in s6 and it’s fine. It’s only when driving really slow and when switching to R from N when cold

How many miles on the car?

[Nico]

If it was the front diff bolt you would hear a clunking sound during load change. Many front diff bolts have been misdiagnosed as "M clunk".

If you have a go pro mount it under the car looking at the diff and watch what it does when you shift gears. Or get a buddy to look under the car while you're shifting in a parking lot. If the bolt backed out or bushing gone bad you should see some significant movement when engaging/disengaging the clutch.

My bet would be the adaptation procedure was not run or there may be a physical issue with the clutch (slave cyl, clutch wear, etc). I would start by bleeding the clutch slave (just because its an easy thing to do) and then doing an adaptation.

Drives fine under power. Have tested out redlining in second and 3rd a couple times in s6 and it’s fine. It’s only when driving really slow and when switching to R from N when cold

[eacmen]

Also:

9. Check front diff bolt.

If it was the front diff bolt you would hear a clunking sound during load change. Many front diff bolts have been misdiagnosed as "M clunk".

If you have a go pro mount it under the car looking at the diff and watch what it does when you shift gears. Or get a buddy to look under the car while you're shifting in a parking lot. If the bolt backed out or bushing gone bad you should see some significant movement when engaging/disengaging the clutch.

My bet would be the adaptation procedure was not run or there may be a physical issue with the clutch (slave cyl, clutch wear, etc). I would start by bleeding the clutch slave (just because its an easy thing to do) and then doing an adaptation.

[Nico]

2nd. i bet this is it.

You think it would cause weird clutch engagements when almost idle as well?

[antknee]

Also:

9. Check front diff bolt.

2nd. i bet this is it.

[cudzich09]

Post a new thread stating you are looking for a specialist shop in Chicago, you will get good advice on where to go and where not to go.

Performance Eurowerks
(224) 676-0756

https://www.google.com/maps/place/Performance+Eurowerks/@42.1810877,-87.9385323,17z/data=!4m12!1m6!3m5!1s0x880fbdd5b9f59535:0xa5bb9f0ca90cce07!2sPerformance+Eurowerks!8m2!3d42.1810877!4d-87.9363436!3m4!1s0x880fbdd5b9f59535:0xa5bb9f0ca90cce07!8m2!3d42.1810877!4d-87.9363436