Strange issue with my Porsche 924S

EDIT: issue solved, but I'll leave it here for posterity. 924/944 guys this may be something you haven't seen before that is of interest to you....

Did a road trip this weekend down to Richmond (about 100 miles), almost entirely cruising down I-95 form DC in the '88 924S. Car ran great the whole way, cruising mostly around 70mph in mostly rainy weather. Anyhow, as I got off on my exit in Richmond yesterday I rev-match downshifted to 4th then 3rd and then 2nd (though I didn't perfectly hit the revs on 2nd), and then braked into a stoplight. As I came to the light, clutched into put the car into 1st, and it wouldn't go in. At all. Put the clutch to the floor still no-go. As I sat at the light, I tried other gears and it would go into 2nd, 3rd, 4th, and 5th with more-than-usual effort and notchiness. Clutch felt pretty normal, it seemed, but hard to tell since I dont' drive this car all that regularly (but had driven it a bit the day before). But I could sit at a light with the clutch fully pressed in and the car in 2nd and the car would not move forward or anything, so the clutch was definitely disengaged.

Also would not go into reverse. I was about a mile from my destination so I just started in 2nd at several stoplights and then parked on the curb when I got there. We took my friend's car over the weekend to do things since I coudlnt' really work on mine or check on much parallel-parked. My intent was to just limp it back home today using 2nd-5th and figure it out when I got home.

This afternoon I left her house, still not able to put it in 1st, and got myself to the highway, where the car seemed to shift fine up to 5th. Cruised for 30 minutes and then hit a rest stop to take the roof off (parking on a shoulder so I didn't have to back out, not having reverse). Car left running while I did that, in neutral with the e-brake on.

Jumped back in the car to get back on the road and intuitively shifted it into 1st.........and it went right in, no problem. Jumped back on the highway, everything felt totally normal with the shifting, clutch, etc. Then I hit heavy stop-and-go traffic and had to stop a few dozen times. Every time, shifted into 1st no problem at all, and throughout the range. Drove all the way home, 3 hours on the highway about half of it in stop-and-go. Got to my house, and car went into reverse just fine as well.

So now I'm stumped. Car has maybe 1000-2000 miles on a new Sachs clutch kit, reputable-brand new slave cylinder  master cylinder (and all new hoses). The clutch feels totally and completely normal now in every way. 

I have noticed for a few week a kind of metallic sound from the car when in gear or idling in neutral (though not with clutch in), which I assume must be the throwout bearing (though that and the pilot bearing were also replaced when I did the clutch). It's not terribly obvious since this isn't really a quiet car and it has a slightly rough idle that rattles some stuff, but still at a bit of a loss on all this.

I will also note that the car has completely new shift linkage hardware from front to back. Not OEM stuff, but the very nice parts from Only944.com that have really been a joy to shift with up til now. I have never missed a gear or had a shifting issue since I installed this stuff.

Thoughts:

1. Somehow an air bubble in the clutch system got knocked into the stream when I downshifted suddenly and eventually made its way out of the system through the M/C and reservoir as I drove and everything heated up?

2. Throwout bearing somehow got stuck in an odd place and didn't allow the clutch to fully disengage, and then eventually somehow let itself free as I drove? Not sure why this would have still let me get it into 2nd-5th gear though.

3. Somehow something shifted in the car, not allowing the linkage to select 1st or reverse. The car has new motor mounts, but the transmission mounts are NOT new, and I don't know how old they are. They are on the list to do this summer. But since the engine and trans are literally bolted together with the torque tube, not sure the trans could move independently enough to cause this. 

4. The rear shift linkage has spherical bearings on it....I guess somehow something could have binded and then unbinded itself? I can't really see how that could happen, but I guess.

Anyhow, I know there are some 924/944 guys on here, so figured i'd ask first before I jump into the P-car forums where I'm sure the answer will be "take it to a Porsche shop" or something, lol...

At any time during the no 1st and reverse episode did you try those gears with the engine not running?  No 1st and no reverse combined with extra effort required to select other gears sounds like classic-clutch-not-fully-disengaged to me.  It's absolutely possible to have the clutch disengaged enough so the vehicle won't move while in gear and the engine running.  If it happens again, stop the engine, put it in first and keep the clutch in, then start the car.

Apis Mellifera said:

At any time during the no 1st and reverse episode did you try those gears with the engine not running?

Yes. With the car parked and engine off I still could not get it into 1st or reverse, but COULD get it into 2nd-5th. I tried this multiple different times over the weekend while it was parked there. Also rolled the car back a foot and tried it again, same result.

And yes, I agree it seems like classic clutch-not-fully disengaging to me as well. But I still can't really see how the problem actually happened (after 1000-2000 miles of no issues since bleeding the system) and then "solved" itself ~50 miles later. 

1. worked fine when I left my house with the car "cold"

2. didn't work after 100 miles on the highway

3. didn't work after sitting overnight with the car "cold"

4. worked fine again after ~50 miles on the highway.

I also checked the line and master/slave and don't see any evidence of a leak. 

Ok... forget everything I just said.  Likely a mechanical problem inside the gearbox  or a shift linkage problem then.  I can't think of anything else it could be because at that point, the clutch isn't a variable.  It's either gearbox or linkage.  Since you recently serviced the linkage, I'd look there first.

Apis Mellifera said:

Ok... forget everything I just said.  Likely a mechanical problem inside the gearbox  or a shift linkage problem then.  I can't think of anything else it could be because at that point, the clutch isn't a variable.  It's either gearbox or linkage.  Since you recently serviced the linkage, I'd look there first.

so you don't think the thowout bearing has anything to do with it, then?

but yeah, plan to check the linkage and what I can on the trans without dropping it. And see if this issue returns.

If the engine is off, the clutch is no longer in play.  Granted it might be slightly easier to shift initially with the clutch in but once the gears are aligned, you can shift all you want into any gear with or without the clutch because the input shaft is not rotating and the various gears stay sync'ed with the layshaft until the engine is started again.  Since you couldn't select 1 or R with the engine off, it can't be the clutch or T/O bearing.

broken fork/borked syncro.

the transaxle I put in my 951S was that way, wouldn’t shift between 1st/2nd without double clutching and absolutely wouldn’t shift into 1st when it was cold.

I don't know about the 924, but on my 911 there's a special tool that centers the shift lever while the linkage is serviced or the cables are replaced.  Is it possible that one cable is longer than it should be?  You could test this by manipulating the shift levers on the gearbox if it happens again.

Bent fork is what I had in mind in my earlier post.  Especially since you where attempting to match revs, which if done quickly and in spirited fashion, sometimes involves forceful, heavy-handed shifting.  I had a Ford T5 that died because of that very scenario.  But, it could be the linkage... and that might explain the self-healing.

well, I think I've figured it out, and it's pretty dumb. Got under the rear of the car and the shift linkage looks fine (car is shifting fine sitting "off" in my garage). And I noticed that where the long linkage main rod comes to the back of the car, it goes through a bracket hat has some kind of hard plastic lining "tube." well, that tube had slipped out the back and looks like it must have been getting jammed between the metal bracket and the linkage bolts at the transmission. There were a few "dents" in the end of it where it was hitting the linkage bolt I guess. So I reached up there and pushed the plastic tube back into the bracket, so hopefully that fixes the problem. In this pic (not mine) you can see it on the left sticking out of the metal bracket. Don't really get why this piece really exists, but it has some little notches on it that are supposed to hold it in place, so maybe they're just a little weak. I'll stick some epoxy up there to hold in in place I gues.

Apis Mellifera said:

I don't know about the 924, but on my 911 there's a special tool that centers the shift lever while the linkage is serviced or the cables are replaced.  Is it possible that one cable is longer than it should be?  You could test this by manipulating the shift levers on the gearbox if it happens again.

Bent fork is what I had in mind in my earlier post.  Especially since you where attempting to match revs, which if done quickly and in spirited fashion, sometimes involves forceful, heavy-handed shifting.  I had a Ford T5 that died because of that very scenario.  But, it could be the linkage... and that might explain the self-healing.

924/944 linkage doesn't have cables. It's a solid rod from the shifter all the way to the transaxle, so the only adjustment is at the rear linkage itself.

and here's a pic of mine....I already pushed the tube back in, but it's pretty apparent that the end was getting smashed into the linkage bolt when I tried to shift into certain gears and was just jamming the whole linkage...

*whew*

irish44j said:

well, I think I've figured it out, and it's pretty dumb. Got under the rear of the car and the shift linkage looks fine (car is shifting fine sitting "off" in my garage). And I noticed that where the long linkage main rod comes to the back of the car, it goes through a bracket hat has some kind of hard plastic lining "tube." well, that tube had slipped out the back and looks like it must have been getting jammed between the metal bracket and the linkage bolts at the transmission. There were a few "dents" in the end of it where it was hitting the linkage bolt I guess. So I reached up there and pushed the plastic tube back into the bracket, so hopefully that fixes the problem. In this pic (not mine) you can see it on the left sticking out of the metal bracket. Don't really get why this piece really exists, but it has some little notches on it that are supposed to hold it in place, so maybe they're just a little weak. I'll stick some epoxy up there to hold in in place I gues.

The dents are to hold the tube in place, shove it forward until it clicks.

its there to help keep dirt and debris out of the “bellhousing” area.

Stefan said:

irish44j said:

well, I think I've figured it out, and it's pretty dumb. Got under the rear of the car and the shift linkage looks fine (car is shifting fine sitting "off" in my garage). And I noticed that where the long linkage main rod comes to the back of the car, it goes through a bracket hat has some kind of hard plastic lining "tube." well, that tube had slipped out the back and looks like it must have been getting jammed between the metal bracket and the linkage bolts at the transmission. There were a few "dents" in the end of it where it was hitting the linkage bolt I guess. So I reached up there and pushed the plastic tube back into the bracket, so hopefully that fixes the problem. In this pic (not mine) you can see it on the left sticking out of the metal bracket. Don't really get why this piece really exists, but it has some little notches on it that are supposed to hold it in place, so maybe they're just a little weak. I'll stick some epoxy up there to hold in in place I gues.

The dents are to hold the tube in place, shove it forward until it clicks.

 

its there to help keep dirt and debris out of the “bellhousing” area.

Yeah, I pushed it in til it clicked (2nd pic). I was referring to the dented-in rim of the end (compare my pic to the Google pics before it), and how it clearly had been getting smashed by that bolt.

Yeah, I saw that on some of the cars, seems to be a bit of an issue with that bolt.

Worn bushings back at the trans can cause that.  Or improper attachment of the rod. There is a notch the lock bolt has to go in to for proper alignment. That bolt should have a pointed end on it that centers it in the divot/notch. Also safety wiring those is a must. I believe the factory bolt had holes in it for that. I know mine does.