Street twin disc clutch failure (ugly)

[NIsaacs]

This application is on a 1995 F-Super Duty, 7.3 diesel and the ZF 5 spd. This was installed 3 years ago along with a rebuilt transmission. Let this be a lesson for you DIY's and even professional clutch installers. I was involved, with my brother, (his truck) we are both considered good mechanics.

The part# on the clutch kit box is right for the application, everything appeared to be a direct fit, replacing an aftermarket single disk, which replaced the oem dual mass. We did NOT measure for depth/clearance, even thou we are both anti dual disk in general. The distributer assured us it was a direct fit, that he installs them all the time. The pictures will show that the flywheel is too shallow for the input shaft/throwout bearing fitment. It needs to be about 1/2-3/4" closer to the transmission.

You can see the input shaft barely reached the pilot bearing and inter disk. The throwout bearing housing hung up on the end of the slider tube. It extended itself too far past the end of the slider tube and locked/cocked there on the return/engage with the end of the slider tube. The clutch never slipped. The stress/mismatch damaged the slider tube/input shaft/input shaft bearing race and front transmission case and started leaking oil, that was the reason for removal.

Per the clutch distributer, the manufacture will send a new replacement, N/C, that they have had some depth/clearance issues with this application in the past. Huh...after all this time?

 

[GCroyle]

Nick,

Hopefully the input shaft is not damaged at the pilot, that's important.

The last two pics really tell your story. Input shaft only went into the spline by what, 1/4" maybe 5/16" or so. And not fully into pilot bearing.

The wear indentations on the bearing face have been seen before on other app's frankly forgot what the likely cause is, have to look in books at work.

IIRC repair kits like this are available for the input shaft pilot surface. This is for reference only, not a recommendation http://www.dieselsite.com/inputshaftrepairkit-zftransmissions.aspx

Gary

 

[HHhuntitall]

Sounds like your distributor or his sales rep sold you a 6 spd ZF clutch......

 

[GCroyle]

The 5 speed spline is 1 1/4" and uses the round collar release bearing shown. 6 speed spline is 1 3/8" with the "square" collar bearing.

 

[NIsaacs]

Sounds like your distributor or his sales rep sold you a 6 spd ZF clutch......

That's what we think, that the flywheel was miss-packaged. The 5 spd input shaft is 9.5" long, the 6 spd is 10.400.

 

[NIsaacs]

Nick,

Hopefully the input shaft is not damaged at the pilot, that's important.

The last two pics really tell your story. Input shaft only went into the spline by what, 1/4" maybe 5/16" or so. And not fully into pilot bearing.

The wear indentations on the bearing face have been seen before on other app's frankly forgot what the likely cause is, have to look in books at work.

Gary

We think the throwout bearing not releasing all the way held more tension on the pressure plate fingers then is normal and wouldn't allow any surface to surface slippage?

 

[HHhuntitall]

We think the throwout bearing not releasing all the way held more tension on the pressure plate fingers then is normal and wouldn't allow any surface to surface slippage?

OH, definitely had bearing pressure... hence the wear into the bearing surface on BOTH sides. I'm surprised it didn't slip, to be honest. But it's pressing the opposite way to create clamping pressure..... It was releasing pressure. The pressure plate just had enough pressure to hold it. That looks like a South Bend, to me, so that's a testimony to what they can be. That's probably the worst worn bearing I've ever seen.... Just like riding the clutch all the time. I've seen it before when someone installed the clutch fork the wrong way, but the clutch slipped, so it had to be pulled apart..... Those grooves on the bearing face are unreal.... WOW!

As Gary pointed out, they use a different size spline. So I'd guess either mispacked or some custom clutch that got shuffled around somewhere.... maybe a return some crooked customer sent back with parts mixed in the box.

 

[NIsaacs]

Update:
Finally got the new clutch replacement, it is basically the same thing. It is about 1/8" closer to fitting. Not good enough! Still 1/2" too short. The clutch distributor don't have a clue so he gave my brother the manufactures number. That conversation mostly went south. That they don't care that his 13" single disk is a direct fit or that he has a home built, cobbled up mix and match truck, bought new in '95. That they have numerous twin disk Ford clutches out that do fit the application. In all fairness, the top two guys were not available for several weeks, so he talked to #3.

He will most likely go back to a single with a ceramic disk.

 

[HHhuntitall]

Hmm, I'm surprised you didn't get better service... I've talked to them on custom trucks dozens of times, and always had great service... that's disappointing...

 

[NIsaacs]

Hmm, I'm surprised you didn't get better service... I've talked to them on custom trucks dozens of times, and always had great service... that's disappointing...

Yes, pretty much my experience too (poor). No return call yesterday, so he ordered a Valair Single, good for 600 hp, they don't make a twin for his rig. I am sure they get a lot of calls that make no sense, so they are probably head shy. You are probably a big distributor so you have some pull. Won't be a third time.

 

[RVTRKN]

My first call would be SBC (South Bend Clutch) for the DD application. At the least, they can give you some insight.