Hole in Trans! Are 5-spd and 6-spd cases the same? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

maytag · 08-03-2018, 08:36 PM

My track day today ended disastrously. See photos below. (Car is an '03 S)

I can only guess the clutch exploded on me? I was down shifting at turn 1 (UMC OUTER) and the pedal went straight to the floor.

So, obviously, 5-spd trans are cheaper and more plentiful. Do any of you know if the front case half will fit the 6-spd trans? If I can avoid buying a complete 6-spd trans, I'll be happy about it! Haha

Sent from my SM-G930T using Tapatalk

78F350 · 08-03-2018, 08:56 PM

They are not the same. Maybe the Audi/VW 6-speed cases from the same year range. Possibly even the front 1/2 of a Quattro.
https://s4wiki.com/wiki/01E_6-speed_manual_transmission

78F350 · 08-03-2018, 09:09 PM

I found pics to compare, I don't think the VW/Audi will work either.

maytag · 08-06-2018, 07:18 PM

Thanks again, to all of you who've responded here.
I'm eyeball-deep in projects right now, so I haven't done much.... BUT.... what I HAVE done isn't working for me.... Sunnuva.....

I got to the point where I was removing the bolts holding the halfshafts to the trans. There are 12 of them, and 10 went fine. the last two are kicking my A$$! they wouldn't budge, so I added some heat to the back flange. I cranked on 'em enough that the socket-cap stripped-out. So I welded an allen-socket to the first one..... the socket broke. So I bought another and welded it to the 2nd one.... the BOLT broke, 1" down from the cap. ::sigh::

SO: I'll cut the cap off the remaining one so I can finish getting the #$@! thing out.... and then ....

What do I risk having damaged adding that much heat to that axle-flange on the trans? Is it riding in a sealed-bearing? or does it have a rubber seal / wiper on it that I could've damaged? I tried to contain the heat, but ... sunnuva.....

SUNNUVA>.......

ok......
I'm calming-down now.

In the meantime, I'm sending back the Beluga exhaust to Beluga for warranty, because it's got something rattling inside the mufflers. They're not being super helpful at this point, in spite of them advertising their one-year warranty (I initially contacted them within 6 weeks of purchasing it).... but as long as they honor their warranty, I guess that'll be sufficient.

I'm making a list of parts I want to replace with new as I reassemble. It's growing. haha.

Thanks again, and in advance, for your help & support!

78F350 · 08-06-2018, 08:57 PM

I've used an angle grinder with a cut-off wheel.
Here's the flange. I'm not sure about the bearing, but it's a pretty big heat-sink.

itsnotanova · 08-07-2018, 05:00 AM

I highly recommend not going with a 5 speed as they don't last very well on a track car. I don't know of anyone that has downgraded to a 5 speed. Go with a 987 five speed if you do though

maytag · 08-07-2018, 05:30 AM

Quote:

Originally Posted by itsnotanova

I highly recommend not going with a 5 speed as they don't last very well on a track car. I don't know of anyone that has downgraded to a 5 speed. Go with a 987 five speed if you do though

No, I should have been more clear; I was thinking I could use the front case half, if they were the same, because the 5-spd trans is more plentiful and cheaper. But that's not an option.

I'll keep y'all posted.

Sent from my SM-G930T using Tapatalk

maytag · 08-08-2018, 11:00 AM

Well......
There it is....

Sent from my SM-G930T using Tapatalk

particlewave · 08-08-2018, 11:03 AM

Yikes...
That clutch disc doesn't even look very worn. What brand is it?

maytag · 08-08-2018, 11:13 AM

Quote:

Originally Posted by particlewave

Yikes...
That clutch disc doesn't even look very worn. What brand is it?

Don't know. It's been in the car since I got it in March this year. Showed no signs.... slipping, nada.

Sent from my SM-G930T using Tapatalk

maytag · 08-08-2018, 11:44 AM

Quote:

Originally Posted by 78F350

Here's the flange. I'm not sure about the bearing, but it's a pretty big heat-sink.

Looks like the seal on those axles isn't too tough to replace.
All in all, I'm remaining positive here. I think I should be able to find someone to weld those holes up. I'll replace the axle seals, and should be okay.

I read someplace that a 987 clutch fits, and is more robust. But now i can't find that reference.... waddy'all know?
Those of y'all who track your cars: clutch preference?

What about a lightweight flywheel? Worth it?

Sent from my SM-G930T using Tapatalk

Sveach756 · 08-08-2018, 03:57 PM

Can you expand a little more on the rattling exhaust? I have the same on a new car I bought and it almost sounds like an AC compressor going bad rattle at times, is this your experience. Feel free to PM me to stay on topic.
Thanks
Shawn

maytag · 08-09-2018, 07:40 AM

Quote:

Originally Posted by Sveach756

Can you expand a little more on the rattling exhaust? I have the same on a new car I bought and it almost sounds like an AC compressor going bad rattle at times, is this your experience. Feel free to PM me to stay on topic.
Thanks
Shawn

I revived a previous thread about "fleabay catback muffler". Let's move this particular conversation over there.

Gilles · 08-09-2018, 11:02 AM

Maytag,

Is there a possibility that the previous owner somehow hit the bottom of the bellhousing (transmission) and that a piece fell off and got inside the clutch assembly creating the chaos you ended with..?

It seems that the bellhousing could be welded, good luck!

911monty · 08-09-2018, 11:07 AM

Have you scanned the DME for stage 2 over revs? Might show something. I saw something similar where an individual thought it was a good idea to leave the trans in first gear while coasting down a hill with the clutch depressed. Can't even imagine the RPM that clutch disk saw before exploding.

maytag · 08-09-2018, 11:13 AM

Quote:

Originally Posted by Gilles

Maytag,

Is there a possibility that the previous owner somehow hit the bottom of the bellhousing (transmission) and that a piece fell off and got inside the clutch assembly creating the chaos you ended with..?

It seems that the bellhousing could be welded, good luck!

Nope. Good thought, but nope.

Sent from my SM-G930T using Tapatalk

maytag · 08-09-2018, 12:26 PM

Quote:

Originally Posted by 911monty

Have you scanned the DME for stage 2 over revs? Might show something. I saw something similar where an individual thought it was a good idea to leave the trans in first gear while coasting down a hill with the clutch depressed. Can't even imagine the RPM that clutch disk saw before exploding.

Thanks Monty. There are plenty of over-revs stored in the DME. And heck, I'm guilty of some of them myself, at the track. But a simple over-rev of the motor (what the DME is recording) shouldn't cause this sort of failure. What you are describing, (coasting down the hill with the clutch depressed )wouldn't have registered at all in the DME.
But you got me thinking:
I did this at the end of the front straight at UMC (Outer Loop). I only got two laps before this happened, but in those two laps, I was hitting 121mph on the straight, then braking to around 85mph as I start to turn-in at turn one, but continuing to brake down to about 60mph at the apex. When I went for the brakes and depressed the clutch simultaneously, then tried to go for 3rd gear, it wouldn't go in. I tried again; wouldn't go. So I took my foot off the clutch to coast through the corner, but the pedal didn't come up.
SO: I can only guess at what speed I tried to grab 3rd gear, because I was braking aggressively, and I can't see my hands in the HLT video; but I would guess around 90mph. That should not be an issue for 3rd gear (that's about the MPH where I upshifted to 4th. And on a different track configuration, I hold 3rd to 98mph before braking). Yes, I rev-match as a force of habit (I'm a motorcycle-guy, it's truly a habit, haha).
So let's say I was REALLY fast on that particular lap, and hit maybe 130mph (I doubt it). And let's say I was trying to enter turn one much faster than before (possible, as I had some clear track ahead of me, having passed the corvette I had been waiting on previously). Let's say I hypothetically tried to grab 3rd gear REALLY quickly, at 100mph. I really don't know if this is plausible... I don't have enough data. I find it unlikely, but possible. If the synchros engaged and rapidly spun-up the clutch to the RPM's it would need to engage 3rd gear at 100mph, then I would think this sort of failure is, well, possible. I guess. But I would hope the clutch could take that sort of spin-up, should'nt it?

I just found someone on Rennlist who posted these top-speeds for the 6-speed, with stock tire size:
1st=~42 MPH
2nd=~70 MPH
3rd=~102 MPH
4th=~127 MPH
5th=~154 MPH
6th=~190 MPH

seems about right. I just can't fathom me trying to grab 3rd at 100mph should create this sort of catastrophic failure.

I'm ready to learn if any of y'all have a different outlook on it?

911monty · 08-09-2018, 03:21 PM

Well Maytag you asked for it! I'll take a stab here (pun intended..)

.

Let's see if we can get some responses. Wish I could separate your pics for annotation would make life easier., But looking at the first pic of the carnage this is what I see.

First your pressure plate did a decent job of containment could have been worse.
Now look at the 10 o'clock position. You can see the friction disk that remained together attempted to extrude between the gap of the pressure plate. This was repeated @ 3:00 and 6:00 but successfully ejected

At the 1:00 position you can see the friction material crushed/depressed as it impacted the pressure plate bolt flange. Also repeated in several areas.

Notice how all but one (at 2:30 still has a small piece attached) of the friction disk to the hub attaching points separated. Now look at the 5:00 position and you will see the only attachment point that still has 2 rivets. Notice the puckering in the center? This is from a tension break, It appears they all broke simultaneously at the same instant.

In summary this appears to be a high speed event to me.

maytag · 08-09-2018, 06:44 PM

Quote:

Originally Posted by 911monty

In summary this appears to be a high speed event to me.

You are very observant, Monty. Thank you for taking time for me.
I don't think that there's any question it was a high speed event.

The question (to me) is what sort of high speed event should a clutch be able to tolerate? Is this a weak clutch, destined to fail? or did I do something that will result in this same result if I do it again? And if the latter, then what, exactly?
As near as I can tell, it occurred either when I depressed the clutch pedal, or when I poked at 3rd gear, going no faster than 100mph (and probably less than that). Even if I had a brain fart and didn't rev-match (I doubt it, as it's so habitual for me, I even do it on the street) shouldn't the clutch tolerate this spin-up?

Sent from my SM-G930T using Tapatalk

911monty · 08-10-2018, 07:24 AM

The number one thing that causes a clutch disc to explode like that is grabbing too low of a gear at too high of a speed. When you downshift, as you move the synchronizer, the blocker ring has to speed up the mainshaft gear, the counter gear, the input shaft, and the clutch disc. As an example, Let's say your car would turn 6000 rpm to go 80 mph in third gear. If you downshift into third at 105 mph, just the action of moving the synchronizer spins the clutch disc to 9000 rpm regardless of what you are doing with the clutch or throttle. Consider that with the fact that there is typically no clamping force on the disc at that point........poof. birdsnest in the bellhousing. Skipping gears is also the main cause of the money shift, where the DME sees stage 2 overrevs when the clutch is let out.

PS: The above is only intended as an example to hopefully draw responses so that mine are not the only opinions. Your actual speeds and RPM will probably differ.