Don't try to save missed shifts!

Fozbo

7M Love
Apr 4, 2005
290
0
16
Norman, Oklahoma
*cliffs at the end :p*

Well a few weeks ago I went down to the drag strip because I had finally worked out all the problems and the maft-pro had been running fine for a few weeks prior. I made three passes, all of them were horrible. I blew apart the upper IC piping in the first two and the third I missed the shift from second to third... and also broke my car. I missed the shift to third and immediately pushed the clutch back in put it in third, and popped the clutch out. During this transition, I heard slight *grind* (miss) followed by a quick high pitched *clunk* when it went in. I was working the pedal pretty fast, so it sounded like one *grind clunk* sound.

Immediately after the run the car was shaking, so I limped it over to the nearest parking spot and took a look at everything I could in the dark, checked all the codes, etc. I couldn't find anything wrong with it other than the obvious shaking (like something is off balance). I limped it home that night (which wasn't too far away) and tested clutch/rpm/other dependencies. It was not dependent on the clutch or gear at all. It was not load dependent. It was however heavily RPM dependent. When I got home, at idle it had a fairly audible tapping coming from where the engine meets the transmission. I parked it for a while since I had a bunch of tests coming up.

I finally got around to looking at it today and this is what I found:

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You can see the cracked bulge pretty well in the picture, but there is also a single crack that runs the whole length of the bell housing horizontal in the picture and up on to where the engine mounts to the bell housing.

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In this picture you can see where the pressure plate has hit along the bell housing. If you put your fingers in there, the gap between the pressure plate and the bell housing is very small.

As far as I can tell, the clutch still works fine, the transmission still shifts fine, it's just the pressure plate and bell housing. All things considered, I think the pressure plate got a little loose and then, with all the pedal working and extreme conditions, the hardware gave out. I don't think it's the flywheel because the starter still works fine.

This is as far as I've gone today, and I will probably be pulling the transmission out this weekend to see for sure what happened and what will need to be replaced. Worst case scenario: transmission shaft bent. Best case scenario: all I have to replace is the bell housing and some hardware.

*cliffs*
Took the supra to the strip, missed third, pressure plate busted and cracked bell housing.

Edit:

This last weekend I was finally able to take the transmission out and see what really happened. Turns out the pressure plate casting broke and tore out a huge chunk of the bell housing. I got everything put back together and I'm back on the road again.

Here is what I saw when I tore everything apart:

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Facime

Leather work expert
Jun 1, 2006
2,716
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60
Corvallis OR
Never heard of misaligning a PP. The locate pins usually do a great job of keeping everything in line. Maybe those sheared off?

Usually a bad shift that causes damage is confined to the gearbox itself, but I have seen some pressure plates explode (did so myself on my 67 Chevelle, turning the flywheel sounded like marbles in a can. But you dont have parts rattling around. Damaged input shaft? Hope not, that more expensive to fix. Good luck on that.
 

IJ.

Grumpy Old Man
Mar 30, 2005
38,728
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I come from a land down under
I'd "guess" it's either broken a drive strap or bent one enough to allow the casting to pop out to the side...

Either way I wouldn't be still driving it till it's inspected and that bellhousing replaced.
 

Fozbo

7M Love
Apr 4, 2005
290
0
16
Norman, Oklahoma
Yeah, the last I drove it was to limp it home from the track. It's been sitting in the garage while I drive an old previa mini van around :p (I'm buying a ~2000 tacoma pretty soon to be my daily driver).

I'm hoping it's not the input shaft for the tranny. But then if it was that, then the pressure plate wouldn't have hit the bell housing and wouldn't have all those marks on it because the pressure plate is attached to the flywheel. Then again, the crank could be bent right at the rear, causing the whole flywheel assembly to wobble around (that would be the new worst case scenario :/). I'll just have to wait to see when I pull it apart and check it out.
 

Fozbo

7M Love
Apr 4, 2005
290
0
16
Norman, Oklahoma
90T04;987660 said:
This happened to my spec stage 3 from the exact same missed shift scenario:

I wonder if it is a SPEC stage 3 thing. I guess it could happen to any brand given the right conditions. It kinda sucks though because the clutch assembly / engine has less than 3500 miles on it and the transmission has less than about 1000 (fully rebuilt). The first obvious thing I'll be looking for is a bell housing; anyone know how much they run?

Looks like I've got less than a month to get it running again so that I can take it to Texas with me for the summer (I don't rely on it for a daily driver though, so no worries, just lack of fun).
 

Rennat

5psi...? haha
Dec 6, 2005
2,844
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Tracy, CA
www.myspace.com
you could try and weld that bell housing back together if you have hook ups. just an idea...

but thats no fun about the PP... im going to be extra careful at the strip now...
 

Rennat

5psi...? haha
Dec 6, 2005
2,844
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Tracy, CA
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why would your friend even bother wasting your money on a spec clutch if hes been through 3 of them... that just seems dumb.

this thread and MANY more like this are why i went with a Southbend DXD Clutch Kit...
 

90T04

New Member
Mar 30, 2005
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Tucson, AZ
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Yea, and I called spec and since I was out of the 1 year warranty period, they didn't care how it failed, it wasn't their problem. They offered to sell me a new pressure plate for four hundred something directly from them.
 

90T04

New Member
Mar 30, 2005
279
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Tucson, AZ
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Rennat;988162 said:
why would your friend even bother wasting your money on a spec clutch if hes been through 3 of them... that just seems dumb.

this thread and MANY more like this are why i went with a Southbend DXD Clutch Kit...

Are southbend clutches supposed to be better than spec? I was thinking of going with an ACT next.
 

Rennat

5psi...? haha
Dec 6, 2005
2,844
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Tracy, CA
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I had an ACT on my last car, i HATED IT. Just plain and simple hated it. The only thing i like about it was that i was FWD, and i could SLIP the living hell out of it...

(and southbend doesnt have lame ass mark up like act and spec)
 

lagged

1991 1JZ
Mar 30, 2005
2,616
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38
new rochelle
i have a southbend 6 puck ceramic clutch disk and i dont like it very much. i holds just fine but it chatters a lot and if you slip it too much it over heats and makes a ton of noise and vibration.
 

lagged

1991 1JZ
Mar 30, 2005
2,616
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38
new rochelle
Rennat;988178 said:
6-puck = chatter. and your not suppose to slip them according to everything i read.
although my friend has a 4-puck and he doesnt really have any chatter...

thats what they say but as we all know on a street car its not possible to avoid slipping the clutch. reversing into a parking space for example requires in most cases that the clutch be slipped.

this is also in comparison to my last car with the same type of disk but from a different company, it was much easier to drive.