New Clutch, CMS and SC: But Still Slipping

[ConstantVigilance]

I have a 6.9 idi with a zf-5 and SMF.

A few weeks back I noticed my clutch becoming softer, or "squishier". After some more driving, I suddenly couldn't go faster than 35 or so.

I found some information about inspecting your clutch pedal linkage and fire wall. Fire wall seemed fine, but my master cylinder push rod opening was warn like an oval and the dowel pin was very warn with about an 8th inch taken out. I found the "Heim Joint Clutch Pedal Modification, By Ron Butts", on this site, and followed the steps.

The clutch still "slipped".

I recently replaced the clutch master cylinder, so I went ahead and replaced the slave cylinder. Made no difference.

I then replaced the master cylinder anyway (they did a warranty swap), and when that didn't work, I replaced the hydraulic line.

Each time I did all these things, I would bench bleed the setup and reinstall. The clutch always felt the same. (albeit SOME difference after the heim joint mod, but still limited to 35mph)

I dropped the transmission. The clutch was warn but dry. The pressure plate "spring" was very warn... and the release bearing was also warn, both were it pushes against the pressure plate and probably an 8th inch marks warn into it from the release fork. The fork was warn also.

I finally ordered a new fork and clutch kit from LUC.

I ordered the "" LUK 07131 (Daily Driver) RepSet®"" from RockAuto.

A previous owner installed the SMF, so I got it machined and reinstalled it.

Today, I finally got the truck back together. First thing I noticed was the clutch pedal felt much stiffer than before. (keep in mind, I have not re-bleed the system sense installing a new hydralic line). This gave me hope, for sure.

Pulling out of the drive I let the clutch out and could hear the engagement of the clutch. Like the sound your breaks make when you free spin the tire when its up on the jack. Its a rubbing sound. I can hear this clearly because I have not reinstalled the tranny shifter boot. I can't tell for sure, but it almost seems like they continue to rub even after the clutch is all the way off. The motor bogs down and gets louder so I can't hear so well.

It DOES begin to engage almost immediately and continues to engage until I'm most the the way up.

But I am still only able to go about 35mph. In fact, the rate of slippage feels no different than before.

I would greatly appreciate any ideas. My first thought, of course, is that the flywheel had been re-surfaced too many times.

Thanks, in advance.

 

[DrCharles]

If your hydraulic cylinders are worn out (or the mechanical joints worn from use), that will not make the clutch slip. You'll be unable to DISengage the clutch with the pedal to the floor. Won't go into gear with the truck stopped, and will grind reverse badly.

Since your new clutch/pressure plate is slipping and there's no oil or grease on it, I have to wonder if it's the wrong one or installed incorrectly... Isn't the LUK 07225 the correct part number for SMF conversions?

 

[ConstantVigilance]

Correct, it is, however, I already had the SMF conversion, so I ordered the kit without the flywheel. The old clutch and pressure plate were the same LUK parts. That is, I ordered the same parts I was replacing.

I absolutely could have installed it incorrectly. I have a knack for screwing stuff up. I wonder what I could have done wrong.

 

[Macrobb]

Get under the truck and push(by hand) on the release fork(effectively pushing the slave cylinder into it's retracted position).
It should take some force(big spring in there) but should move slowly at least another 1/2 inch.
Can you do that? If it doesn't move at all, the hydraulics are holding things up. If it moves, it's something else.

 

[ConstantVigilance]

Macrobb, thank you for the response.

Sure enough, I couldn't budge it. It's an awkward position to reach up and push on it, but I pushed with everything I had and it didn't move.

I'm thinking maybe I did that clutch-pedal-heim-joint modification wrong. not leaving enough slack in the pedal. I'm going to remove it and shave some of the shaft off and reinstall.

I'll let you know how it goes.

Whats strange is that it was behaving the same way before that mod; albeit the clutch was torn up.

Thanks again... I miss my truck

 

[Oledirtypearl86]

Did you do the throwout bearing when you replaced the couch. Where the new clutch is slipping I'd check and make sure everything is adjusted right I'm not sure on the adjustment process but my clutch starts to grab with kicker about 1 inch off floor and is fully engaged 2 -3 inches from top also just thaugut of it I had a 99 7.3 with a zf6 and it was slipping pretty bad turned out to be the slave cylinder I found this out by having someone push the clutch pedal while I watched the engagement process and noticed a few seconds later the slave would kind of jump a 1/8th inch but it wasn't fully extending

 

[ConstantVigilance]

Problem solved!

Macrobb pointed me in the right direction. When I did that heim joint modification, I didn't take enough of the shaft off. It only took about an eighth of an inch of excess shaft, to engage the clutch enough to slip it.

It never occurred to me that this was a problem because the clutch was slipping exactly the same amount before I did the heim joint modification.

Thanks for the responses, gotta love this forum.

Sent from my SM-G930V using Tapatalk

 

[IDIBRONCO]

I'm glad to hear that you got it fixed easily.