I replaced the clutch while the transmission was out. New LUK SMF clutch that replaced a LUK SMF clutch. After replacement, the truck would not take gear from neutral, and crept when started in gear. Engagement is like 1/4" off the floor. The clutch hydraulic system was not opened during the transmission R&I.

After R&I, the slave cylinder developed a squeak. I accidentally hit the clutch while the slave was not attached. Fearing damage, it was replaced. After a thorough bleed, the truck behaves exactly like as described above, no change. Out of caution, I replaced the master too. Maybe I over extended it when I hit the clutch? After a thorough bleeding, the truck still behaves as described above.

As usual with my stuff, there's some weirdness.

Number 1, the throw out bearing was installed backwards when I removed the transmission. The fingers of the pressure plate had been riding on the fork. Despite this, the clutch had felt good.






Since the issue was present as soon as the transmission was reinstalled, and did not change after the clutch hydraulic system overhaul, I don't think this is a hydraulic issue.

I did my best to bench bleed the slave cylinder. After installing I let it hang and gravity bleed. I let it hang and cycled by hand the push the air up thru the system to reservoir. Then I bled with the clutch. Satisfied there was no air left, and with the problem not changing, I went to get a master cylinder too.

This is weirdness Number 2. The master cylinder installed in my truck is, according to the parts stores, for a gas burner. The diesel listings all had the outlet of the master on the end towards the front of the truck. Mine has the outlet straight down. So I bought one for a gas burner. It was working before, right? Again, thoroughly bled the system, throwing a pressure bleeder into the mix.

Absolutely no change. Pedal basically engages at the floor, truck creeps in gear.

I did notice that the clutch fork wobbles a little, video here.
https://drive.google.com/file/d/1w06...usp=drive_link

I know a common issue on these trucks is the pedal bushing, but this truck has the heim joint mod. I checked, and there is no play in the pedal.

If I messed up the install, I think the only place would be the little spacer/plate/whatever that shares the flywheel bolts was on the back/clutch side of the flywheel, and that's where I put it back. Throw out bearing was reinstalled opposite of the above pictures, and like the diagram below.





Where do I go from here? I think a new clutch fork is a good idea because of the damage, and can be done without pulling the trans again. Did I put the little spacer in the correct orientation? Does it really matter?

Is the gas burner clutch master weaker than the diesels? I really should have just gotten the master/slave assy that is pre-bled, but that ship has sailed.

If anyone followed my other thread about diagnosing a misfire, Sign of bad injector(s)?, a set of injectors from Rosewood cured the misfire. its still not running 100% because I haven't been able to drive it since the injector install.

As always, thanks for any assistance.

 

Sure you got the clutch disk facing the correct direction? I also dont recall any spacer behind the flywheel but I use a Southbend clutch and only used what was sent in the kit. This is the kit and everything that came with it. https://www.southbendclutch.com/clutches/1944-5OK-7869/ maybe LUK does the SMF different I don't know.

 

The tin spacer does go between the engine block and the flywheel, which if I read right, is ow you installed it. The single mass flywheel/clutch I have used had this side towards flywheel printed on the clutch plate. Is it possible the it was installed backwards as 96SD mentioned? Was the old clutch operating as it should? You stated that you have the hemi joint installed, but are the bushings in the peddle assembly good? Those slave cylinders can be a bitch to blead sometimes, maybe there is still air in it.

 

This is a response to 96SD


Oh man, the clutch. The new clutch was not marked with a "flywheel side". The old one was. So I matched it the old disc that was labeled.

BUT...

I forgot the large bellhousing adapter/spacer when I installed the flywheel/clutch/pressure plate. So they had to come back off. I was pretty frustrated with myself during reassembly. It's possible I wasn't as particular the second time around.

I'll try to see how the disc is in from the bottom, hopefully I can confirm without pulling the transmission.

It never crossed my mind. Thanks for the insight, this is why I posted.

 

No, I put it on the clutch side, the flywheel is touching the crank. That's where it was before. I want sure if it was a spacer, or a plate to spread the bolt force evenly across the flywheel. But whoever put it there also put the throw out on backwards, so...

No play in the pedal, good and tight.

It's possible I may have put the clutch is backwards, see my above post.

I'm 99.9% certain the issue is not Hydraulic. The system has been thoroughly bleed, and the problem was present even with the old hydro system that I had never opened.

 

I had a brain fart, I was thinking bell housing bolts not flywheel bolts when talking about the spacer. I believe that spacer was used on the dual mass flywheel, and is not needed on the single mass units. The single mass flywheel kits I used had new bolts for the flywheel to crank and did not have that spacer. Sorry for the confusion. I don't think that the spacer would cause your problem, and you have it placed right.

 

Poke your head under the dash and look at the zigzag bracket (name slips mind) and depress the clutch pedal. I am not wondering if that slipped or moves a hair.

I had issue with my dually and that after heim joint deal. I had to replace that bracket.

 

I had that on mine for years, even after replace clutch

My pedal assy was shot and ordered a new one

red is where my bushings were gone

 

Thanks for the input, guys.

The clutch disc center has a "flat" side and a "domed" side. The flat side is the flywheel side. The domed side faces the pressure plate/rear of truck. Here are photos of the old disc, the flat side is clearly marked "Flywheel side".




I can look thru the pressure plate and clearly see the "domed" side of the clutch disc. The clutch disc is installed in the correct orientation.

Here is a video of the pedal in action. There is just a hair of movement at the white bushings. The swing arm, or zig zag, is not slipping.
https://drive.google.com/file/d/1-1B...usp=drive_link

I'm both relieved and disappointed the clutch is not in wrong. So glad I don't have the pull the trans again, but it would have been nice to get come closure.

So, what now? I think I will proceed with the new clutch fork. You can see in the second picture the tines of the fork have some wear.

 

Is it possible there is a different throw with this clutch? In a way that the swing arm will need to be adjusted? Thats the last idea I have as long as the hydraulics are bleed properly. When I put my swing arm on I made sure to get rid of all the play in the master and then tightened the new arm.

 

It's been a while since I installed my clutch, so my memory might be hazy or bad here. I do not recall a "spacer/plate/whatever" on the clutch side of the flywheel. I don't think it's related to your problem based on your description of where it goes, but I am still curious about it. Did the OEM clutch and flywheel have such a spacer?

What does it look like when you have a helper push the clutch pedal while you're watching everything with the inspection cover removed? Does it look like the slave cylinder is not getting enough motion through the pushrod, or does it look like the clutch fork and pivot are doing a bad job of translating that motion to create separation between the clutch, flywheel, and pressure plate? Something else?

 

The clutch set removed from the truck was a LUK SMF kit seemingly identical to the LUK SMF kit i put back in. Theoretically, the only thing I changed was flipping the throw out bearing around.

We can back up to just after I installed the transmission, because nothing I've done since has changed anything. At that time, the clutch hydro system had not been opened. I simply popped the slave off the trans, and popped it back on later. The pedal was unaltered from when I took everything apart to reassembly. The only things I had changed were the flywheel, clutch, pressure plate and throw out bearing. I confirmed that the clutch fork is seated properly on the pivot in the transmission, and the little spring clip is engaged.

Since then I have replaced or confirmed proper operation for the pedal assy and the clutch hydro system.

So it seems like either a faulty part or user error when assembling the flywheel/clutch,pp.

Luk has a tech support line, I'll try giving them a call sometime tomorrow.

I just don't understand how the clutch was working so well with the throw out bearing on backwards, and the clutch fork engaging the pressure plate fingers. Then I "fix" it and it doesn't work. Story of my life, LOL

 

The spacer looks like this, but only about 1/8 thick. Its just thicker than sheet metal. Its diameter is just larger than the bolt pattern on the flywheel. I confirmed on the workbench that it would not interfere with the clutch. It sits down in the hub of the flywheel. I put the flywheel on the crank, put the spacer on the flywheel, bolts go thru both spacer and flywheel. I have done VW clutches that were setup this way, so it didn't seem strange to me.

Farmert said that the spacer was likely used with the DMF, and not needed with the SMF. I placed it back in the same location as it was removed, on the transmission side of the flywheel.




I don't have a helper to help me with the clutch for a day or two. I did watch the system in motion as someone pushed the clutch. Everything seemed to work ok. I didn't think the measure the actual throw of the fork at this time. The truck didn't have the transfer case in yet, so I wasn't aware of the issue at that time.

 

Wonder if they had to adjust the swing arm to match the goofed up TO bearing? Hmmmm

 

When I replaced the clutch master, I removed the swing arm. I marked it before removal. When putting it back on, I positioned it to take the slack up on the pushrod. It went back on the same spline that it came off, and my marks lined up. I tried to move it one spline counter clockwise, but this would preload the master/pushrod a little which I can only assume is bad.