clutch problems again.
 

So I have a 91 that has a freshly rebuilt motor (S5 NA) and a trans and driveline out of a 88 vert. It has a new slave cylander, good working master, slightly worn clutch disc and pressure plate, new pilot and throwout bearings. The first problem I ran into was that the clutch release fork had slipped off its pivot point on the transmission in the bell housing. It would go into gear just fine, but when I let off the clutch the car would hardly move. After fixing that problem I let off the clutch pedal and no movement what so ever.

I have plenty of movement in the clutch at the slave and fork, the car goes into all gears just fine, no excessive noise, all new or good working parts.

I'm stumped.:scratch::blush:
Hopin for some help here guys.

Thanks in advance, Rob.:icon_tup:

Could be the clutch disk was installed backwards... Seen this before... Either that or the pressure plate is still being held down by the throw out bearing/fork

Good idea, but I had a friend suggest that I check that and the clutch is installed properly. It is and ouuble checked.
I have also tried installing a different fork thinking the plate was still being held down. After doing so there was still nothing.

Is the clutch just that worn out? Is the clutch slipping or does it just feel like there is no engagement?

About 2k miles on the disc and pp. I don't think it would be worn out. :)
It is not slipping. The hydrolics are functioning properly from what I can tell and the transmission is going into gear just fine, just when I let out the clutch pedal NOTHING.

If its not slipping it may not even be engaging. Did you get your flywheel resurfaced? Is the disk contaminated?

Improperly torqued pressure plate??

Correct. It is acting as if it is not engaging although it seems as if everything is in order.
Yes the flywheel was resurfaced. My machinist took about .004 off.
Everything is very clean in the bell housing and rear plate. Not likely to be contaminated.

Did you confirm that both the flywheel surface AND the pressure plate mounting surface was ground down?

Yes. The disc and PP only have about 2000 miles on them. I scuffed up the pressure plate slightly with steel wool ensuring there were no hot spots or any uneven wear.

I mean on the flywheel itself. If the flywheel clutch surface was machined and the pressure plate mounting surface (on the flywheel) was not then you could have this problem.

Or if the pressure plate mounting surface was machined less then the clutch surface.

All of the friction surfaces are fine. :)

I am not talking about the friction surface.

Why would you machine down the pp mounting surface. Never heard of that before...

A picture of inside the tranny bellhousing showing the throwout bearing and shift fork would help in the diagnostics.

Allow me to demonstrate my zomg paint skills.



As you see, if you don't machine them at the same rate you won't have very good clamping of the clutch.

Gotcha. I see exactly what you are saying. Nice artwork BTW that helped alot.
Do you think .004" would make that much difference on a disc that move MUCH further than that and alows for much more wear that that?

The full length of the clutch pedal travel is nowhere near the amount of travel required to fully dis-engage the clutch. If you have access to another manual car try seeing how little you can move the clutch and still shift with no issues. Be sure to do it with bare feet to really understand how little you need to press the clutch to disengage it.

Plus its process of elimination, if everything else is good about the clutch system except that.....you may have found your problem.

Rob,

Are you using clutch components from a S5 or S4?

Hey Doc. :)
IIRC they are all S5 clutch components.

I was hoping you were going to say S4 as their is a difference in the pressure plate, Release bearing and even fork. Although I don't know what the difference is between the fork and the bearing the pressure plate should be a height difference which would explain the no engagement issue.

Still has to be an engagement issue that the disc is not fully seated when the pedal is up. I have not played with a S5 transmission in my FB swaps just S4's so I don't know if the pivot ball for the fork sits in the same spot as the S4 and that may be causing the issue. This is one of those things that I would have to be there to look at it. :)

Come to think of it I will have to check. Since the trans is an S4 and all else is S5 I may have to change the pivot ball and fork on the transmission. That sounds like where the problem lies.

Can anyone confirm a difference in S4 / S5 transmissions and release fork pivot balls?

I doubt that the S5 components are causing the issue. If the PP height was different between S4 and S5 then aftermarket companies would have to make two specific flywheels for S5 and S4 cars.

In regards to the fork, plenty of people are running S5 trans on an S4 car without engagement issues so I also highly doubt that being a problem.

The pressure plates are different part #'s. The disc are the same for the N/A and height differences will cause this issue as I had it happen to me when they had a boxed wrong pressure plate. I installed everything and had the same exact issue as RW has. Took it apart and compared the pressure plates and the height was different. Got a replacement and installed it and no more issue!:)


Like I stated the release bearings are different for the S4 & S5. I don't know what the difference is because I have never compared them nor have one to compare at this time. This is for "Stock" parts and the aftermarket have their own components.

Also how do you know that those using the S5 trans on their cars are not using the S4 clutch components including the fork? The transmission may not be an issue but the components of the clutch can be. :-)

The S4 and S5 forks are definitely different. They are different Mazda Part numbers. The pivot pin is the same.

If it is an S4 trany you need to have an S4 fork.

The slave cyl is the same for all years 2nd gen N/A.

Also all the aftermarket clutch kits and components including pressure plate and throwout bearing i have used have been useable on either an S4 or S5.