mesprit87

When I planned to change my DMF I initially didn't plan to change the clutch disc because it had been changed by the previous owner at the dealer in 2009 and the car didn't add a lot of mileage since.
When I pulled the clutch, my initial idea was confirmed, lots of material left.

It's just a few days later that I tried the disc on the transmission shaft... ouch.
Lots of play and the disc would wobble on the shaft. It seems the splines on the disc wore more on the protruding end of the splines than near the disc.
If you look closely you can see a double indentation at the bottom of the splines.

I inspected the transmission shaft and everything seems ok, the disc is out in the bin of course.

Now what could cause a damage like this ?
Could it be that when they replaced the clutch the DMF was already half gone?
What type of damage (other the the noises) can a bad DMF can do?

I'm just making sure that I don't miss anything before I put everything back together and of course gain the knowledge of you experienced lot.

Thanks

nine9six

Im no expert but...
I'd put a mic on the trans shaft to make sure the OD of the splines are to spec. Not sure if the trans shaft spline measurement, should be over wires but it would stand to reason, as 60 deg V threads are measured over wires...It almost looks as if the spline shaft is undersized on the OD, as evidenced by the 70ish% contact patch to the disk splines.

Or...

As the rubber in the DMF fails, the sensor pickup on the OD is not in proper time/sync with the actual time of the motor and causes misfires. Maybe these misfires are hammering the softer splines as engineered into the disk?

Are you throwing any CEL misfire codes?

Can you post a pic of the shaft splines?

NP993

Splines sure look bone dry for a clutch that was serviced only a few years ago.

driveline

Fretting damage. The dmf was not doing its job, and thereby probably doing a bigger disservice than if it had been a plain old flywheel. The couch hub is softer and is the sacrificial part in this case.

Replace the clutch. LIGHTLY coat the splines with grease. You don't want it slinging onto the clutch surfaces.

driveline

clutch hub. Gotta love iphones

nine9six

Yes, per engineering design.

Perhaps the failing DMF rubber portion was so shot that any off-on throttle was causing a hammering effect to the clutch hub internal splines?

At this point the cause is mute, as the clutch needs replacing as previously stated. Time for an RS clutch and LWF, if 96 ot later? ☺

mesprit87

Thanks for the replies guys, I will try to snap a good picture of the shaft.
Nine9six, can you elaborate on the over the wires technique? Never heard of it.
I did consider going with the RS setup but since the clutch was [I]supposed [I] to be new, I prepurchased the flywheel only. I have to plan this stuff since I buy my parts in the states when I go across. The dealer was asking 2400$ just for the part...
So I will give it another go with the original setup and see how long things hold up, maybe the RS setup for the next time around.
NP993, I noticed that too on removal, nice rusty look and dry splines.
Stay tuned
Luc

nine9six

Luc,
It looks like this...You measure with a micrometer over the wires.

mesprit87

Thanks for the info on the measurement, and to answer your initial question, no CEL codes, well nothing that will light up in the dash at least. I'm still getting setup to read the codes.
Here are the shaft pictures, you can see wear but IMHO nothing to be urgently concerned about.


Would you happen to know what values I should be looking at for the shaft? I understand these values could vary depending on the wire used... I have access to .032"-.041", typical aircraft stuff.

Thanks for your help.

nine9six

Unfortunately, no...The measurement is dependent upon the OD of the splined shaft and number of splines, just like a thread. Calculation and spline chart would be in a machinist handbook, or in a google search.

I would say your splined shaft is ok as long as you cant feel, with a scribe or an awl, any wear ridges, where the disk wear marks are on the shaft. Also, I would stone the shaft splines to clean them up.

The spline shaft, is by design, much harder and tougher material, than the disk spline. The cheaper, replaceable part is designed to give up the ghost, as opposed to the more costly splined shaft.

If measuring, dont forget to convert to metric, if not using a digital measuring device with an in/mm button.

P.S. Are you in aircraft/aerospace biz? If so, do you have access to a machinist who will measure for you? Depending on your access to machine tools, there are go/nogo gauges for quick determination of in or out of spec tolerancing.

mesprit87

I am in the aircraft biz but the biz is big enough that I could not bring the tranny in...
Here is a link to my machine
https://rennlist.com/forums/aviation...t-popular.html

Thanks for your time
Luc

vincer77

Don't mean to hijack thread but I am in process of replacing dmf setup with an Aasco midweight flywheel and rs clutch/pressure plate. I found a good deal (well maybe) on a used rs setup. The Disc Plate Has What I Consider Uneven Wear With outer Section SHOWING More Wear THANKS inner. Is this normal?



I put a straight edge on the pressure plate and see that it is higher on the outer section.





When I pulled my flywheel, I found that after 45000 miles it looks almost new.



Thoughts?

There is about 1.6mm material above the rivets on the rs clutch. Should I just install and forget or reline disc and resurface pressure plate?

mesprit87

Hmmm,
The contact surface remains the same but I think it is abnormal wear. Now I don't have enough experience with Pcars to tell you if they have a tendency to wear like this, maybe guys with more experience will chip in.
As for if you're good to go, I would say yes but it all depends on when you want to drop it again.

OverBoosted28

Not an expert, but did my clutch last year. While looking for the parts, I looked at a couple of used items. They looked alright, but I came to the realization, that I did not want to have ANY chance of a lesser part failing prematurely. Go with a new disk and PP. if the flywheel isn't perfect, get that also. If it was a race car, and you'd planned on pulling it after a while, then maybe. Otherwise, do it right, one and done!
To answer your question, no that wear is not normal. It should be pretty uniform. That looks as though the PP didn't have enough clamping force, or even might not be releasing completely and it may have been "riding" on the disc. Good luck

nine9six

Lol, I was thinking on bringing the machinist and hand measiring tools to the splined shaft.

Nice machine!