Ok, so it's been a while since I've played in the FTE sandbox, my apologies! Been busy with other things, which means: 1. no issues with the truck (good thing!); 2. busy at work (good thing); and 3. PMS budget re-routed to other hobbies (not necessarily a bad thing, depending).

Anyway, coming home after a trip this weekend out of nowhere my ZF-6 wont engage! Downshifted coming down a hill, let out the clutch, engine at idle and nothing doing on the transmission. Pulled over (that's the short version...), nothing engaging in any gear. Clutch pedal has "normal" pressure, but I think I recall that in these trucks that pressure is actually provided by the pedal system and not the pressure plate/clutch. This is very new to me, as prior to this any failure I've seen in the clutch system has failed ENgaged, and not DIS-engaged. Nearest I can make of it would be a throwout fork/linkage failure of some kind.

Any other input?


Background (the long part):
[Note: in the following descriptions I use "6th" for top gear and "1st" for lowest gear, contrary to what's displayed on the stock ****. If this is non-standard here, let me know and I'll change my frame of reference for the future.]

Holiday weekend camping/4-wheeling trip to Marble CO out of Denver CO. Left Denver Fri afternoon with the camper loaded (est ~4500#, prob higher with all the * my gf has squirreled away in there...) and flat towing the Jeep (est ~4000#+). Lots of traffic on I-70 W, and several times caught up in it. The 2 biggest pulls are the Eisenhower tunnel approach and Vail Pass. DP in 40T hit 1350 on the EGTs pretty quick, and had to back off to stock several times. After about 14mo of owning this truck, this would be the first time I've ever had to firewall the go-pedal! Most uphill time spent in 5th, with a rare drop to 4th due to traffic and not being able to keep speed. EBV did a great job holding the truck back on the descents, with a downshift 6th to 5th to help out on the steeper sections. Was slightly chagrined by the fact that my buddy with a newer Cummins (Dodge mega-cab w/ shortbed, much lighter camper but his 4-runner is slightly heavier than my Jeep) was making better time than I was. But then once we got to Glenwood Springs for dinner found out from his wife that pretty much everything was redlined including his transmission. I bumped 1350 on the EGTs a few times, but everything else was just warm.

Spent a great weekend in Marble, some decent 4-wheeling, some GREAT pics (will post later once I get a chance to pull from the camera), perfect weather. Stayed in the Bogan Flats campground in White River NF, just outside of Marble. Beautiful site, will definitely be back. Anyway, all good things must come to an end, and on Mon it's time to head back. Checkout isnt until 2:00 (very nice!). So a leisurely morning packing up, lunch in Marble (the Cookout Shack has GREAT bbq!), and then the ride home.

Surprisingly, traffic was very light the entire trip (prob a good thing). Vail Pass E-bound is a gradual pull until the last bit, and was able to keep her in 40T until the very end where I had to drop to stock and a very short stint in 4th. The Eisenhower approach is another good pull E-bound, but here was able to stay in 40T and some feathering to keep the EGTs below 1350. As before, the EBV did a great job on the descents to keep the speed in check with very rare use of the service brakes and an occasional downshift to 5th for help.

Here was the fun part:
On the last descent (fortunately!) into Denver, engaged the EBV just over the crest of the hill and rode that most of the way down in 6th. Near the end there's a steeper section, decided to drop to 5th for the extra braking power. Dump the clutch, downshift, release the clutch... NADA. Engine at idle, truck in gear, no compression braking AT ALL. WTF? I'm stunned here. Back to 6th, back to 5th, even 4th. Nothing. Pumping the brakes to keep the speed down, but still completely confounded - never seen a clutch failure DIS-engaged before. The gf starts to get a little freaked here (we're already passed the last runaway truck ramp!), but she managed to stay composed. Well, she managed to stay quiet anyway! I wasnt too worried because the service brakes were doing well, we were nearing the bottom, and there's enough uphill at the bottom that I knew we'd get stopped ok. Getting home after that was my concern...


So we got to the bottom with the speed still well under control, rolled off the Morrison Rd exit and on to the shoulder and stopped. Slight brake smell, but not really bad. Truck runs fine, but any gear selected from R, to 1st, to 6th gets absolutely nothing to the drive train. No noticable issues looking underneath (not like I'd be able see a clutch problem anyway, but you gotta look - heck, I even had the hood up at one point even tho I knew darn well the issue wasnt under there). Driveshafts all connected and looking fine. Locked hubs and tried 4WD but still no response.

Again, this is the first time I've seen a clutch/pressure plate failed in the DIS-engaged mode. Before I've only seen failed engaged, and you can limp home in a gear low enough to start out in with the engine off. The only thing I can come up with is a throwout fork failure, and I'm open to other input as to what to look for.

I figure I'm already in for dropping the xfr case/transmission, if it's not already the issue should I plan on changing out the clutch plate as well while I'm in there (just turned 129k)?

Thanks for readin the ramble, and even tho I'm now dealing with a broke truck I'm EXTREMELY pleased that it failed when it did - on the very last descent on the way home. No ruined vacation here! Just some inconvenience and the embarrassment of being towed home by a Dodge. Tho I'll admit that I'm impressed at how the Cummins did pulling both it/camper and my F350/camper (the girls drove the toads home) about 10mi to the house, and mostly downhill. Tho he wouldnt tell me what his temps were on the uphills and I suspect he was pushing it trying to show off. His truck, not mine.


Anyway, input on what to check out appreciated!
J

Edit - What the "rig" looked like during the trip:

 

Logically, I see three possibilities: 1) The throwout fork jammed in the released position, 2) The center tore out of the clutch disc, and 3) The input shaft of the transmission failed.

Throwout forks usually fail by buckling at the mid-point where they contact the throwout bearing. That means that they leave the clutch engaged. In order to have your problem, the fork would have to be intact, but jammed in the released position. Try to remove the clutch slave cylinder. If it won't come out normally, it could be jammed in the released positon. If it comes off, check the fork to see if it is sitting in the proper position. If everything looks OK, proceed to remove the tranny.

Once the tranny is out, you can check out the other two possibilities. I think you would have heard/felt a major "bang" if either one of these had happened, so I am hoping that the clutch release system is the culprit.

 

Good info Jock, thanks! I hadnt considered (2) or (3), mainly because like you mentioned I would have expected some noise associated with the failure. This was nothing! I had the radio on, but definitely not blaring and would have heard something like that, I think. The only noise I heard was at one point messing around with it on the side of the road I did hear a moderate "klunk", but at this point the failure had already occurred - and it could very well have been the Jeep shifting on the tow bar.

I'm going to jockey the truck into my driveway tonight, and hopefully I can check out the clutch slave.

Jim

 

So are you saying it goes into gear, but you have nothing??

If that is the case I think it would be a tranny issue, not a clutch issue.

Even with a clutch failure you should have been able to get it into gear to help you slow down. My clutch is in need of attention and therefore have not been using it much at all the last couple of weeks. Finally ordering parts this week so I should be back to pushing the pedal.

Edit: Just read about the possibility of jammed fork. I had not thought of that!

 

Ok, my background is all in mechanical clutches, and maybe that's why I'm not seeing what's going on here.

In the hydraulic world, what are the chances this could be the slave cylinder?

 

Correct, "shifts" normally - ie I get the same friction/bumps that I would normally encounter, so it feels to me like the shifter is operating the guts of the tranny - and not just flopping around disconnected.

Based on the symptoms I'm inclined to say a busted input shaft, however I would have expected a decent "knock" and/or jolt at the time of the failure, plus I would also think there would be some residual noise when in gear with the clutch disengaged (the shaft parts spinning against each other), but maybe that's expecting too much. Same with the center-clutch disintegration.

Also, my understanding is that the ZF-6 is a pretty beastly tranny, and it certainly wasnt being abused at the time (or at all, since I've owned it) - like I said, when I let the clutch out on the hill I felt/heard absolutely nothing, just eased right out with no compression braking and engine at idle. Quite the moment!

Still wondering about the slave cylinder possibilities, but I need to research a bit more into hydraulic clutch functionality...

J

 

I've had a master cylinder failure where the clutch went to the floor and didn't come back up. When pried up, the pedal was useless. My recent slave cylinder failure was caused by a small leak. As the slave wore out, it became difficult to shift into gear. Pedal felt normal, but with the engine running it didn't want to go into gear without really pushing on the shifter (most notably 1st & 3rd). Engine off it shifted through all the gears fine.

My hydraulic failures don't seem to match your issues. Pulling the slave is the easiest thing to check first and will hopefully give you a place to go from there. Any chance your short throw shift kit messed up somewhere?

 

That's definitely something to consider, tho as I said the shifting "feels" normal just sitting there, not sloppy at all. Just like it always has. There's definitely guts moving around in the tranny when the shifter is operated.

Added a pic to the original post of what the "rig" looked like ready to roll, and here's what we did to get it in the driveway and up on the RV pad [once again, VERY happy I installed a front hitch!]. Note: my buddy's Tojo is geared much lower than my Jeep, plus I couldnt drive both at the same time...

 

The slave cylinder should turn counter-clockwise about 1/8th of a turn then come out. You might be able to see the fork with a mirror and flash light. If the slave won't turn and come out, then it has jammed somehow. It should be easy to check those.

 

The slave came right out. Here's what it looks like, I assume that's bad?

I also assume it's best/easiest to just replace with the pre-filled master/slave assembly, too.

 

If it is just extended all the way, then it is not necessarily bad. The plastic tab thingy on the end is what holds it together for assembly and it is intended to break the first time you use the clutch.

Is the shaft bent, or just cocked to the side because the piston is extended all the way? If you push the rod back in, does fluid come out in the master cylinder resevoir?

If you look in the clutch housing with a flashlight and mirror, do you see anything wrong?

 

You had the same experience that I had.
The shift fork wore out in my transfer case and the transfer case dropped to neutral.
No going anywhere under my own power and I was 110 miles from home on the top of Mt. Rainier.
One $500.00 tow bill later I was home.
Cost me $450.00 to buy the rebuild kit for the transfer case.
The thread that I started with pictures:

https://www.ford-trucks.com/forums/3...ce-needed.html

.

 

*F*, I was hoping it was just the slave, but reading the first post in Dan's thread, sounds dead on to what I'm seeing. Off to read the rest of the post (thanks Dan!)...

 

The repair job is easier than it looks.
I was very apprensive at first, but at the end of it all the hardest part of the whole job was getting the halves separated.
It required a porta-power spreader to get it apart.

 

Not familiar with the porta-power spreader, can those be rented somewhere?

Also, reading the rest of your thread sounds much like my issue. Playing more with the t-case now, during shifting I feel the "normal" bumps moving between 2H, 4H, and 4L, plus the dash lights (4WD, Low-Range) operate as expected. Would this still happen during the shift fork failure?

And recommendation on sources for rebuild parts (in addition to drivetrain dot com)?

Looks like I get to dive into my t-case (ironically, I was hoping to be working on my Jeep t-case this spring instead - installing a 4:1 in place of the stock 2.73:1).