Flywheel/Clutch losing Balance

[NC325iC]

I had my flywheel balanced before I put together my s52 swap into my car. I used the m20 clutch/flywheel/starter. (it was brand new and i didnt want to waste it, wish i hadnt have done that)

Recently i have been getting some vibrations around 2000 rpm under load. I assumed that it was the driveshaft binding slightly and beating the CSB to death due to improper drivetrain alignment as it only seemed to happen under load. So i ordered a set of revshift swap mounts and trans mounts.

Now I know that these mounts are urethane and thus transmit more vibration than stock rubber, but i was more concerned with the alignment of the engine in the chassis so i accepted this. However, the vibration did not go away and has clarified itself to be engine related not drivetrain related.

Is it possible that my flywheel or pressure plate could have become unbalanced? what else could cause a vibration at 2-3k rpm?

[jeffnhiscars]

Unless you lost a bolt I can't see how they could go out of balance. I would also think the symptms would get progressively worse the higher the rpm.

[NC325iC]

yeah but i would think losing a pp bolt would make some additional issues as well. Thats not to say i havent had clutch issues with this setup, because i definitely have. I have an e36 flywheel and clutch that I will have to install next week.

Just wanted to see if anyone had any ideas.

As for getting worse with more rpm, i dont think that is necessarily the case, 2-3k rpm could be a harmonic causing worse vibration then it could calm back down to a less noticeable value. Also since changing the mounts i havent had it up that high.

[TobyB]

I've had pressure plates break before- that gives you some bad vibes.
The friction surface gets loose (a strap breaks,etc) and flops to one side of the bell.

The 2-3k range is low, though- can you completely rule out misfire, lean spot, etc?
Or a misphased/ misaligned driveshaft?

hth

t

[NC325iC]

i can rule out the driveshaft, as it does it while stationary.

I do not think there is a misfire as i was able to drive it without issue before changing the mounts. After changing the mounts the vibrations are too apparent for me to want to drive it.

[berlow94]

So let me get this straight, you had a problem with drivetrain alignment and needed precision made motor & tranny mounts? And you bought from R3vshift? Hahahahah! Sorry to hear that!

Is the M20 flywheel lightened at all? Aftermarket aluminum flywheel? a certain amount of rattle/vibration is normal with a light flywheel/clutch.

[TobyB]

After changing the mounts

well, I think you've nailed the first thing to check right there, if it does it in neutral...

..but yes, broken straps in the pressure plate will do it at idle, too.

t

[Sh3rpak!ng]

Sounds like its a balance issue of the rotating assembly and my money is on it being the pressure plate as TobyB suggested. I suffered the same issue. In talking to bimmerworld/UUC both were not surprised to hear I'd broken stock e36m pressure plates (bent straps). Apparently it's relatively common especially with single mass flywheels.

and FWIW I've had the revshift 24v engine mounts for 2 years now without issues.

[e30rapidic]

I broke a pressure plate strap on my m20 single mass pressure plate. It made a horrible click/scrape around the inside of the bell housing.

[NC325iC]

Quick update:

I started pulling it apart to put the new flywheel and clutch in. I found that when i tried to lower the back of the trans it wouldnt budge. Turns out the the intake manifold was hitting the booster, so I bolted the trans back up and started to pull the intake off to get it to lean properly. Found that the booster and intake are either touching or very nearly touching at all times.

So now I have a new theory. Perhaps the rubber mounts were allowing enough movement (with the rubber mounts there was maybe 1/8-1/4 clearance) under load to allow the intake to contact and transmit engine vibes direct to chassis. So when I replaced the mounts and now it contacts all the time i feel the vibration all the time.

That being said I'm going to continue swapping the clutch out as I have had other issues with it. But now I dont expect to find anything wrong with it.

[NC325iC]

Pulled the trans this morning. As expected clutch looks fine. TOB is shot, but the rest looks good. Looks like there might be a little bit of burn on the flywheel (light brown areas).

The biggest issue and most terrifying thing i discovered though. When I used the m20 flywheel I assumed that I would need m20 flywheel bolts due to the varying thickness of the flywheel. WRONG!!! Warning to anyone using m20 flywheel in their 24v swap, make sure you get the correct length flywheel bolts. There was so little thread engagement on these bolts that they barely got into the loctite, I was able to remove 2 of them by hand and the rest with a small electric impact wrench... these things should be pretty difficult to remove. Scary thought to think what could have happened.

Anyway I am going to continue with the clutch job and probably space up the driver side engine mount to gain clearance to the booster. Hopefully it will fix my vibrations.

Pictures : https://goo.gl/photos/R9xyQEVkmkaR72mx8

[NC325iC]

So I'm worried about using the flywheel spacer that I have. It seems like it may be too thick. Is there any risk in not using it?

Sent from my ONEPLUS A3000 using Tapatalk

[TobyB]

Yes.
The face of the flywheel is pretty soft- the 'spacer' is hardened to keep the bolt
heads from sinking into it. If you don't use it, the bolt heads can sink, the bolts
lose torque, and then... well, you know the rest.

Getting longer bolts shouldn't be too hard- BMW used lots of lengths over the years,
from early 2002's to S54's, and I THINK they're all the same thread.

RealOEM wins for this sort of thing- it usually gives you the details of the bolt

hth

t