Odd shifting behavior

Greetings all,

My '87 TC 5sp (98K mi) has a perplexing issue.    It runs and drives beautifully for the most part.   But it seems that for every time I start it - whether it's been parked for a week or 20 minutes - within, say, the first 10 shifts, it suddenly won't go into (whatever) gear without double-clutching.   After that, the transmission is fine for the rest of the drive, over however many shifts / hours / miles.    It's just this one random fluke "keep you on your toes" moment, within the first few shifts after a start! 

As random and unbelievable as it sounds, I've been dealing with it for a few months now in a variety of situations to rule out all sorts of variables.   The "gotcha" gear could be an up or a down shift, anything from 1 thru R.   It could be while rolling, or from a stop.  It could be uphill, downhill.  All temps.   First drive of the day, or the 5th errand in a run.  The only thing that's somewhat random about is if it'll happen in the 1st, 2nd, 3rd... ...10th shift... either way it's guaranteed to happen "soon" but not the "same Xth".    It's the damndest thing... especially since it never happens again, and everything is smooth and troublefree otherwise.  

I've checked the fluid in both trans and clutch, etc... all seems well enough.   Does anyone have any clue where to even begin to look?

To only stutter once and not in a predictable gear, then smooth out is weird. I wonder if a tranny fluid change would improve it, can't hurt. I had 1st gear synchros go out a few years back. That was definitely predictable but only affected me when stopped, going into 1st gear. I rarely use the clutch when shifting, up or down.

"I wonder if a tranny fluid change would improve it, can't hurt."

The tranny was about 1.5 qts low when I got the car, but managed the 500mi pickup drive (I didn't realize the fluid was low then) OK. I very soon made that discovery, topped it off, and it was much improved... save this odd behavior. It's not getting better or worse; I agree mechanically it almost defies explanation.

"I rarely use the clutch when shifting, up or down." Heh, I'm jealous. I'm far too old for this to be my first manual car, but it is! Better late than never but I've a ways to got before I get that sort of confidence.

Clutch free shifting is a habit I got into in the early 90's when I was big trucking. In those, the clutch was only useful to get rolling from a stop. If you tried using it between gears, the tranny still wanted the engine RPMs to sync with it or it would grind, so, you just quit trying. The T5s in my bird and 88 Mustang both shift effortlessly without the clutch, you just have to get the hang of it.
FWIW, the T5s only hold about 3 qt so being 1.5 qt low is substantial. If it were mine, I'd change it anyway.

Greetings all,

My '87 TC 5sp (98K mi) has a perplexing issue.    It runs and drives beautifully for the most part.   But it seems that for every time I start it - whether it's been parked for a week or 20 minutes - within, say, the first 10 shifts, it suddenly won't go into (whatever) gear without double-clutching.   After that, the transmission is fine for the rest of the drive, over however many shifts / hours / miles.    It's just this one random fluke "keep you on your toes" moment, within the first few shifts after a start! 

As random and unbelievable as it sounds, I've been dealing with it for a few months now in a variety of situations to rule out all sorts of variables.   The "gotcha" gear could be an up or a down shift, anything from 1 thru R.   It could be while rolling, or from a stop.  It could be uphill, downhill.  All temps.   First drive of the day, or the 5th errand in a run.  The only thing that's somewhat random about is if it'll happen in the 1st, 2nd, 3rd... ...10th shift... either way it's guaranteed to happen "soon" but not the "same Xth".    It's the damndest thing... especially since it never happens again, and everything is smooth and troublefree otherwise.  

I've checked the fluid in both trans and clutch, etc... all seems well enough.   Does anyone have any clue where to even begin to look?

I've experienced this. In my case, it was the clutch slave cylinder. The fact that you are mostly having issues at startup clinches it for me, because it sounds like it needs to build up pressure.

It's not the most durable device, for what it does. It's made of an extra-strong type of plastic...but it's still plastic. Even the bleed screw's threads are--the plastic of the body of the thing and very easy to strip, which is why manufacturer LUK advises you don't even use the bleed screw. You bleed it by pushing in the pushrod and letting it come back out, while a helper watches the flow of air bubbles in the clutch master cylinder.

I've had my T5OD transmission out more times than I can count, to either replace the clutch assembly (over time) or rebuild it. The rule I have followed is: ALWAYS replace the slave cylinder. This, after so many times of pushing on the clutch pedal and getting...nothing. The thing is too quirky.

It's like $20 most places. I would replace that and see what happens.

If it were me I would start with bleeding the clutch system and see what happens. If nothing changes, I would replace the clutch slave cylinder. Hopefully that will fix your problem because the master cylinders aren't available anymore so you'll be looking for a used one or making some modifications. In my experience, slave cylinders fail more often than master cylinders.

Hi all,

Thanks for the suggestions! After spending too much time fighting the blasted MC4350 on my MarkIV, I finally turned attention to installing a new clutch slave cylinder on the TC today as suggested earlier by anasazi4st. And then when the pedal simply flopped around I realized "huh, probably need to bleed it after all" as spittinfire coincidentally posted in timely fashion.

In my defense, the new part did not include instructions, and Ye Olde Bibles De Haynes Y Chilton didn't mention bleeding as part of this. So I was rightly confused when the separate bleeding section mentioned bleed screws and a brake-style procedure, when there are no similar screws on the slave cylinder. After studying the part and the worm screw under the line fitting, and experimenting with the cylinder I removed, I finally realized you can gravity bleed if you hold the cylinder a certain way? So I did that, got the pedal feel back, and all seemed well on some errands around town, yay!

I wish bleeding brakes was that easy, haha.

For good measure I pulled the piston out of the old cylinder and it was heavily coated in oxidation, not to mention the body being coated in grime, suggesting it had been slowly leaking for some time.

Thanks again for the tips guys.

Hi all, have an update, and some questions / concerns:

So have finally had the TC out a bit more after the slave cylinder swap and what I can say is that, to me, the shifting action feels a little more… snappy? Precise? Smooth-when-it-works?

“When it works”? Yeah, my concern: it hasn’t fixed the problem entirely
Occasionally I have to push the clutch pedal seemingly through the floor before it will shift… sometimes even this is unsuccessful so I essentially have to stall if it’s not possible to double-clutch. But most of the time, it’s fine!

This seems to happen most at slow speeds, and/or the 1-2 shift. Never have issues with 3-4-5. Sometimes it won’t go into R until I row through the other gears first, or let the car roll a tick. Either way, the issue still favors that “soon after starting” time period, as opposed to having driven for a while. Get along down the road a bit and it shifts like a dream! Unfortunately my wife had a bear of a time after starting and getting caught in unusually bad city traffic last week (as I witnessed).

So I have to say my original problem is unfortunately unsolved, if not a little worse. The trouble is, manual transmissions are still new to me so I’m confused as to what the cause(s) could be. Master cylinder? Clutch itself? Syncros (please no)? Or did I possibly get a bum slave cylinder?

Of course I’ve noticed that the TC-only master cylinder essentially became NLA coincidentally about the same day I got the car, go figure! And while I’m not afraid of mechanical work, if I do have to rebuild the clutch or something… well I’ve been reading and it seems there are all kinds of parts gotchas out there now. So I’m hoping for some advice toward a solid troubleshooting path to follow, before I fall too deep down the rabbit hole of chasing parts and other unexpected issues.

Thanks!

Pressing the pedal that hard into the floor suggests to me there is still air in system. Bleed it again to see if this still continues.

I have a habit of always shifting to 2nd before 1st or reverse. 1st will sometimes feel like it is "locked out" if you are going too fast. Reverse will grind if the car is rolling at all forward.

Hi all, I have an update and question. First the question: how can one distinguish if an issue is with the slave, or the master?

Reason I ask is I have bled, and rebled, and rebled, and still the problem(s) persist. The original "double clutch a random shift" issue is gone. But it's been replaced with tricky behavior in 1st and reverse. I can clutch in just fine... but if I have to hold for more than say 5 seconds (as with parking) I won't be able to release without stalling. At speed, all shifts are great! But clutch pressure bleeds off at low speed.

With the car out of gear, I can lightly press the clutch to the engagement point... and the pedal will sometimes (but not always) slowly sink to the floor with the dead weight of my foot. It shouldn't do that? If I pump it a few times it'll firm up more, but never stay that way.

So clearly, air is still bleeding in. I can think of 3 reasons:

1) I still haven't bled it right?
2) the new slave is defective
3) the master is the problem... which, sigh and $#!& I'm apparently screwed.

Any advice is appreciated!