Solid subframe bushings clunking

[Bmac]

Hey guys,

I'm having an issue with clunking in the rear after the install of solid aluminum Turner rear subframe bushings. I had a local indy shop to do the install as I don't have a press and I knew I wouldn't be able to do it myself. It was good for a bit but after the first few weeks I noticed a clunking sound which I'm pretty sure is due to the solid subframe bushings. Everything else in the rear end has been upgraded over the last couple of years.

Has anyone else experienced this? I did a fair amount of research before deciding to go solid as this car is my daily driver and I didn't want a drastic increase in NVH, but didn't see anything about clunking. My indy told me he's seen it in E9X M3's previously. Pretty much all the other mounts and bushing in the car have have been upgraded, but none of those were solid because it seemed like they would all cause NVH issues wehere people with solid subframe bushings said that wasn't the case, and that's also the place where they make the biggest difference in performance. It tightened up the rear end considerably and if it did increase NVH, it didn't do so by much, but I don't want to live with the clunking from the subframe. Does anyone have any suggestions that might help? I'd like to fix it if possible, but if I can't I will have them pulled and replace them with something different.

 

[martymil]

I tell my customers and friends dont do these as the vibrations can be annoying and tend to loosen other things around the rear end.

When something vibrates it causes other things to loosen and you have to keep going back and checking everything.

Put the car on the hoist and pull the wheels off and check the hand brake shoes inside the rear discs and all the nuts and bolts.

Check the rear body brace and exhaust hangers

 

[Bmac]

Thanks for the suggestions. Right after the subframe bushings were done the e-brake cable snapped and was replaced, but I will take a look at the parts you suggested. The car does vibrate more than stock, but I don't think it's enough to cause any issues, and it's really not bad considering most of the suspension, mounts and bushings on the car are stiffer than stock.

The car has Bilstein B8 shocks with Dinan springs, 335is motor mounts, Rogue transmission mounts, Dinan fixed camber plates, M3 front sway bar (with stiffer bushings), M3 control arms front and rear, M3 diff bushings, Monroe rubber rear shock mounts, Megan Racing toe arms, Meyle HD end links all around, and a defiv-style diff lockdown kit. Other than the subframe bushings which were the last thing done and replaced stock bushings with Whiteline inserts, I've deliberately avoided anything too stiff or too low because I can't live with a lot of NVH. I wanted something more competent for the track without compromising comfort too much because track & autocross time makes up a fraction of 1% of my total driving time.

 

[ShocknAwe]

Check the metal mounts around the "bushings". They can crack sometimes.

 

[martymil]

its not so much the nvh but the road and the bushes are transferring the shock directly into the subframe and connected parts.

Every little sharp bump that use to get absorbed by the rubber bushes now gets directly transferred into the chasis.

Also they create stress fractures in the metal just like solid camber plates where repeated hits will cause strut tower failure and that is dampened
by the spring and shock.

 

[The Banshee]

Check the metal mounts around the "bushings". They can crack sometimes.

This is especially true depending on how the inserts are installed. They are hell to install. The shop that did mine made an aluminum block to reinforce the subframe to prevent cracking and bending of the subframe itself during installation.

 

[Torgus]

I tell my customers and friends dont do these as the vibrations can be annoying and tend to loosen other things around the rear end.

I and many others have ZERO NVH from the solid subframe bushings. All of the newer BMWs come with solid subframe bushings iirc from the factory.

What exactly have you seen loosen on the rear end?

Now solid rear diff mounts with LSD and a lockdown kit? Sure NVH, as to be expected and possible diff clunk when going into reverse.

@Bmac When do you get the clunk? Is it repeatable? I highly doubt it is from the subframe mounts.

 

[silverstreak18]

Put them in the freezer over night, put a bit of lube on them and they press right in with the proper tools. They don't add any noticeable NVH by themselves. The biggest NVH increase is going to come from a diff brace or solid diff bushings.

 

[martymil]

The problem with factory diff bushes on m3 rear ends when used in high hp applications they tend to break the diff bolts and under certain stock applications.

I've broken at least 4 x 10.8 grade bolts and 2 x 12.8 grade bolts that hold the diff in place, since swapping to solid diff bushing I havent broke once since and I run the weaker 10.8 grade bolts now.

I have a tiny little whine from the solid diff bushing but I can live with it, I've been in a car with solid frame bushings and stock diff bushings and the nvh was unbearable on our poor roads compared to mine but it was nice to drive on good roads.

So it really depends on what type of roads you normally drive on.

 

[houtan]

Any updates?