Gear Rattle Question

[Heylin]

Due to a slipping clutch, I had my stock clutch on the Mitsubishi Colt upgraded at Autoclutch (Refaced with Kevlar\Carbon), Flywheel resurfaced, Uprated pressure plate fingers).

Prior to upgrade there was only slight rollover \ gear rattle in neutral, after upgrade when running it has massive gear rollover in neutral, and all gears, especially when coasting off throttle.
Tried some different fluid mixes to no avail.

So I have had the whole lot removed for inspection

- strip box down (check all internal bearings for play) all OK
- replace input shaft bearing (slight growl)
- balance pressure plate, disc + flywheel (apprently this doesnt get done at Autoclutch)
- replace transmission to body torque rod (bushes were shot)
- refill with Redline Gl4 75W85

Havent run the car yet as waiting on clutch balance to happen, but thought id check to see what else I should be looking at before putting it all back together.

Realistically everything seems to point to the clutch side of things (most likely an imbalance) as that was the only thing changed, but the other components may have magnified the issue.

One key symptom was the sound changed from really bad to bad depending on where everything locked up when clutch was released (balance ??)

[sergei]

In my opinion gear rattle does not come from imbalance, but the nature of L4 engines with flat cranks: the power pulses are not even (also applies to H4 and V8 with flat plane cranks).

Slightly off-topic but here is video explaining the solution to this problem:
https://www.youtube.com/watch?v=A42YsR0ZYLI

You could solve this by following:

use massive flywheel.
use softer centre on clutch.

[Heylin]

Yep I understand about engine torque pulses and gear lash \ clatter.

What I dont understand though is the issue barely existed prior to changing the clutch slight rattle in neutral, now its 4 times louder, in all gears, and especially bad when deceling \ coasting.
ie I went from a 2/10 to an 8/10 on the rattle scale.

Bearing in mind the plate and disc are still factory, just with uprated fingers and facings. The hub damper springs are factory, the flywheel has not been lightened (other than the thousandth of a inch they take off with resurfacing)

The only things that come to mind are

- imbalance of the clutch disc, plate or flywheel (leading to extra torsional vibration)
- vibration transmission increased using kevlar vs organic
- possible misalignment on assembly ??

[matt dunn]

I had the same thing happen on my EVO years ago when I owned it and put a good clutch in it.

Although I had put a solid centre clutch in it you are probably seeing the same noise.

Are you sure that the springs in the plate are still standard?
It seems that it will be that the springs in the clutch plate are so stiff that it is not absorbing the speed pulses from the crankshaft,
which rattles the gears back and forward in the gearbox.

Does it only do it on decel at lower revs?
not when on decel high in the rev range?

In the end I went back to a standard clutch in my mitsi to make the car quite again,
as the noise was so bad that I wouldn't have been able to sell it.

[Heylin]

Damper springs are stock, autoclutch only did the facings on the disc.

The rattle is coming from countershaft gears, happens mainly on idle, all low gears on anything but constant throttle, and decel in all gears at all speeds.

Really bugging me as the whole ordeal so far has costed nearly 1000 dollars, and im lucky enough to have a friend who owns mechanical shop to do the install and dropping of the box. Box out 3 times so far in just over a year.

[matt dunn]

Seems very weird then.

[Heylin]

Update, got clutch back from balancers today and they drilled out about 5 grams from flywheel, and also a few spots on the pressure plate.

They also noted the spline/hub on the disc had both axial and radial play... Not sure if this is normal but being Sachs brand I wouldnt run it past the germans to engineer some self correcting offset and aligment into the spline/hub.

Next step is to look at identical new unit and determine if normal.