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Over the last few months I've noticed that it has been increasingly hard to get into 3rd and 5th and this gets worse as the car (gearbox) warms up. Took it to the local main dealer who acknowledged the problem but simply replaced the plastic cup at the front end of the shift shaft where it connects to the bottom end of the shifter. Insisted this was the problem and all was sorted.
Of course its not and really there was little difference. I know my car really well having had it for almost 18 years and paid attention to every odd noise or off "feel" that comes up. And this was definately not fixing itself. Anyway short cut to the point is I took it to a local independent who clearly knows his stuff and is predominatly air cooled. Pretty much in 30 mins it was clear there's a problem inside the box. Dropped the engine and box and opened up the front end of the gearbox.
The good news is the planetry gear cage and the main "tube" (not sure the correct name) are fine. I'd read scary stories about the tendancy for these to crack and drop the gears after which its more like a tumble drier with a box of rocks inside. But it turns out the plates in the front clutch pack are completely knackered and mostly polished smooth with just a few looking okay. Not sure on the rest of it as that's as far as they got by Saturday but I'm expecting syncros and dog gears needing help. Also of course removing the engine exposed a number of annoying leaks and other minor issues which may lead to a rebuild of sorts.
Another potentially big car bill for the year. This one has actually been pretty low maintenance all it's life and I try to keep it in 100% condition so I guess its due some attention. Crossing my fingers and everything else that its not going to clean me out.
Some very rough pics but I'll try to post more as things progress.
Make sure the pins in the planetary gear are welded in place before it goes back together. No brainer since it's out. The reason the planetary gear fails is because the pins loosen up and slip out of place.
Also- as far as the shifting goes...i know you found an issue in the box, which is great that it's being done...but also make sure your engine mounts aren't blown, as this causes notchy shifting as well. Wouldn't be a reason for the car not to shift in or out of 4 and 5...just causes it to get clunky.
You will need to change to Valeo discs as the original types are no longer available. It’s all in the workshop manual. One annoyance is that the system has a range of spacer washers to choose from based on the measurement of the discs so you either order the lot or order parts in two steps. Also be prepared for parts on back order. Good luck.https://rennlist.com/forums/964-foru...refurb-16.html
Thanks for the tips. John, I've read and re-read your excellent posts on the similar issues you had with the C4 box - at least it seems my planetary gears are okay although I'll definitely suggest the pins are welded in for peace of mind. This morning it appears there's a problem with the reverse gear selector mechanism which seems to be very notchy and stiff.
Can you explain the symptom when warm in some more detail?
My gearbox, when hot, makes the left to right movement (1st to 3rd to 5th movement) and vice versa very difficult. It is as if the shaft slowly gets clamped down as the heat increases.
My mechanic has diagnosed it as an issue in the box and I had him put in a spare (used) box. Now two years later I am ready, time wise mostly, to have the original box rebuilt. Car is a 93 C4.
However, he has a concern about not having access to all the tools the Porsche manuals prescribe. Even the dealer here does not have them.
So I am following this thread with interest to see if I learn anything of value for the rebuild. So if you have any info on the tools used while taking it apart and putting back together, please do share and I thank you in advance for it.
And BTW your pic in the previous post is of a part he suspects as well of causing the hard shifting.
Last edited by Navaros911; 08-29-2018 at 08:21 AM.
I'll certainly do my best to post up as much detail as I can with emphasis on the tools involved etc. The shop owner doing the work is a friend of a friend/soon to be close friend of mine and I'm sure he'll fill me in on any uncertainties. In the past I've always taken the car to the Pcar main dealers here in Taiwan believing that at least they will have the correct tools and manuals and being a main dealer should carry a greater responsibility to do a good job. Unfortunately this ethic has worn off over the last few years and they seem to neither care nor have the expertise and interest in the air cooled generation. Good at changing the oil on a Cayenne but that's about it.
My car is with one of the best independents here recommended by several air cooled friends and what's more he speaks excellent English! Such a relief to be able to call him up and chat about it instead of relying on my rather appalling Mandarin abilities. I do fine in my office envoronment but the vocab I need to discuss transmission details or mechanical subtleties is just not there!
The part you mention is the reverse shift lever and should operate smoothly like a rifle bolt. Right now its rough and sticky etc and is part of the problem apparently. Unfortunately they did a leak down test on the engine as there's been a lot of oil accumulating in the intake plenum recently so the piston rings are suspect at the moment. Also seems down on power. They'll check once more tomorrow before removing the heads and cylinder barrels at least, to get to the rings.
This is turning into one of those spiralling rabbit holes at the moment.....!
Can you explain the symptom when warm in some more detail?
My gearbox, when hot, makes the left to right movement (1st to 3rd to 5th movement) and vice versa very difficult. It is as if the shaft slowly gets clamped down as the heat increases.
My mechanic has diagnosed it as an issue in the box and I had him put in a spare (used) box. Now two years later I am ready, time wise mostly, to have the original box rebuilt. Car is a 93 C4.
However, he has a concern about not having access to all the tools the Porsche manuals prescribe. Even the dealer here does not have them.
So I am following this thread with interest to see if I learn anything of value for the rebuild. So if you have any info on the tools used while taking it apart and putting back together, please do share and I thank you in advance for it.
And BTW your pic in the previous post is of a part he suspects as well of causing the hard shifting.
Sorry mis-quoted your post Navaros. No offense Rocket Rob....!
I hear you with regards to the expertise for the aircooled slowly fading, particularly so in developing economies.
I have similar issues here and could take the car to Dubai, but then I would be flying over every so often to see the car and discuss with the Porsche Classic dealer there.
That said, I have a great mech (30 min from home) here that used to work for the dealer (and Ruf subsequently) and has more experience on aircooled cars than 1999 and up washing machines (pun intended)... he is willing to go at it and figure the tool situation out, but I prefer to be a little more prepared.
Oh and he is English... so I know exactly what you mean with language barriers as well.
In any case, I wish you the best with the undertaking on your end.
OK an update on the ever expanding issues with my car. What started as perhaps a shift linkage problem has rapidly expanded into a top end overhaul and gearbox total rebuild.
The gearbox was dropped to fix a problem with the shifting ie was sticky or notchy particularly going from 2-3 and 4-5. In dismantling the front part of the gearbox the valeo discs were removed and found to be largely worn out or even worn down to mating metal to metal surfaces. These need replacing as a total set. So far I think the syncro rigns are okay but obviously the rest of the gearbox was dismantled to check for any other wear or damage. In the process we've discovered other areas of wear but luckily the planetry gear set and cage etc seem to be okay. In fact wear on the gear sets looks generally okay so I've escaped major cost there I hope.
Taking the engine out to get to the gearbox its clear there has been substantial blow by from the piston rings as surplus oil from the cylinders has been blowing out via the pressure release and therefore back into the inlet tract and later all over the top of the engine. 3 cylinders are low on compression so the heads will be removed to bench test them and repair and the cylinder bores removed to replace rings and check for any other wear. The mech thinks I've been substantially down on power for some time which kind of matches to my seat of the pants performance gauge.
One point in all this is that the clutch disks for the four wheel drive and even the front diff disks are regular maintenance items and need to be checked/replaced on C4's periodically. They don't last for ever and are a substantial cost when needed. Similar to an engine rebuild in some respects. My car is pretty low mileage (38k miles) but its had a lot of city driving and short trips etc which may have made it worse. Reading through other posts there are a few detailing the similar issues with the C4 gearbox so I wonder if this is something that we ought to be factoring into long term maintenance plans and costs with our cars?? It's not something I was fully aware of until all this happened.
Long time no see. I have the similar shifting issue into 3rd as yours. Which shop did you go to? Might ask them to check mine.
Thanks!
Patrick
Hi Patrick! Long time no see but glad to see you still have the 964.
I took it to Albert at GMS in Nankang. I'll pm you his cell number. He is by far the best guy I've had to work on my car in the 18 years or so I've owned it. He has a good team of people and they really know what they're doing. Price is better then the main dealer of course but the main thing is they care. I've used the main dealer almost exclusivly until now and wish I'd swapped earlier.
08-28-2018, 02:33 PM
C4 Gearbox woes
