[craigawoodman]

Hi,

I recently participated at the Porsche Clubs (of Australia) at Bathurst event over Easter. Bathurst is a magic racetrack/public road - so it is rare to be able to race on it. It is essentially a hill climb and track in one as it is built on the side of a large hill - so you climb it, traverse the ridge line and then descend it. There are long straights up the mountain and down, and engine throttle percentage is high, along with overall vehicle speeds. I have just posted a clip on YouTube - you will see a 935 and GT1 from the museum at the end of it (I am chasing a 944 most of the time).

My problem is this - on the Tuesday morning run, after around three to four laps, the gear selection went from its normal smooth action to being very hard to get gears. Initially it was second, then effectively all gears (using second, third, fouth and fifth around the track). After a slow lap to enter the pits (a lap is 3 minutes long) and the long pit exit and drive back to the paddock area, the problem went away. My mechanic has looked at the car and found no problems and it does not exist any more.

Anyone have similar experience before. It got to the point where I was having to get physical with the gear lever to get it to slot home.

Thanks,

Craig Woodman

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[DaveN]

Stupid question - you don't have a short shift block (Stuttgart) on the tranny linkage that possibly got quite hot and fouled the shifting by binding? After all the track you describe sounds like it would have given the engine and trans quite the workout.

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[rhudeboye]

Mine is not a track car but I also have an intermittent shifting prob. It comes and goes but seems to show up most often on down shifts. I have had extensive tranny worrk done on my car and I actually suspect that thats part of the problem.

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[craigawoodman]

Hi,

It is a standard linkage, no short shift block. The problem orginally started on downshifts (2nd gear), then progressed through the whole shift pattern for both up and down shifts, only to dissappear once I backed off and returned to the pits. Oil was drained and nothing found, car has been driven since with no problems at all?

It has got me baffled. This is the only time it has happenned. Our normal track days are around 7 to 12 laps of a circuit where lap times are normally in the minute mark. This was around 30 minutes on the track, with the problem occurring past the halfway mark.

Thanks,

Craig

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[banditsc]

What kind of oil are you using in there? Also what was the amibient temp like that day?

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[rhudeboye]

FWIW- I never force it into gear. ie if it wont go into 2nd, while keeping the clutch in, I can move it to 3rd or 1st then go back towards 2nd it slides right in. Almost as if something wasn't aligned right until moved the gear away then back.

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[pure&simple]

Could it be heat related? I lost a 2nd gear synchro last year and noticed that it was much easier to get in gear when cold.

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[rhudeboye]

Not mine. I can shift 1-6 with the car OFF and every now and then it will get hung up and not throw into a particular gear unless I back off, go to another gear then back towards that slot. Some type of alignment issue.

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[pure&simple]

I used to have that kind of problem grabbing first from a stop. Sometimes I would have to go back to neutral, let out the clutch, push it in, and then try grabbing first again. I don't think I've had that problem since the 2nd gear synchro was replaced. It was actually the synchro hub that was the problem - it was binding occasionally and then got really bad after a not-so-smooth downshift at VIR.

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[craigawoodman]

Hi,

Ambient temperatures were around the 25 degree Celcius mark - so for over here - not too bad.

The oil is a premium synthetic oil. it was drained and had no obvious problems and new oil added.

One of the Fitzgerald Porsche 968 RS replica's was there and he commented that he had a similar problem and went back to a mineral oil (non synthetic) and it fixed the problem.

I did not do the last track session, so I do not know if it will come back under load. The next track day (next weekend) is now a double booking and it does not make sense to travel down to it. So it will be another month before I get the car on a track again.

Normal shift effort is minimal, this was really heavy to get out of neutral and into the gear indent and engaged.

Thanks,

Craig

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[craigawoodman]

Ah - mechanic has gearbox out of car. Syncro's on second gear stuffed, along with the gear (and the entire shaft that it is part of). Mega $$ in repair costs - replacement shaft alone is $1,500, plus syncros, bearings etc. Still entire gearbox will get a freshen up with new syncro's throughout, bearings, etc.

Not sure whether it is chicken or egg here. Did the clutch failure around 7 months ago stuff the syncro's which in turn has stuffed the gear, or did the gear somehow stuff up which has stuffed the relatively new clutch. Interesting indeed.

So I am up for a double whammy - new clutch and also gearbox overhaul.

Car has 125,000km on it. It never does standing starts and has never had a problem with the gearbox until now (in the almost four years I have owned it). Looks like I will now have to plan for next years motorsport events as this year is now gone to the dogs. The supercharger is looking more promising - but after this repair - the bank balance will have taken a beating.

Best keep this from the wife.

Craig

Sorry, I should have also added - the friction material on the clutch had completely sheared off the clutch with only around 7 months of use and about 2,000km (although almost all on the track).

So not entirely sure which occurred first or why both have occurred - something strange indeed.

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[Lear35A]

As someone up to his ears in costs for engine overhaul, I feel your pain. What happened that you decided to pull the gearbox apart? Your previous post was that everything was ok after things had cooled down.
BTW, I've been in Gladstone. Took a helicopter from there out to some small island for a little diving. I just love Queensland.

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[pure&simple]

Sorry to hear it. [img]style_emoticons/<#EMO_DIR#>/sad.gif[/img] I am told the 2nd gear syncro is a known weak point. When RSB did mine, they had difficulty sourcing a replacement... I wish you all the best of luck finding the parts you need.

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[craigawoodman]

After Bathurst, took car to mechanic - he drove the car - no problem found. Took the car home and off the trailer, put it in the garage. When it was time to go to the next motorsport event, took car out of garage (had been in and out a couple of times for a wash) and drove it to work where I keep the trailer. I had problems getting second gear again. Lots of bad smell - like fish going up the driveway - thought clutch.

Took car back down to Brisbane and got the mechanic to look at it again. No problems driving it the 15km or so to the mechanic. He could find no problems. Did fours runs on the day and had troubles getting gears with the lever baulking. At the end of the fourth run, when I came back into the pits, the clutch was juddering and felt like it had dropped a spring or damaged the fingers. So I parked it up.

Mechanic looked at the clutch to see if this was the problem. The friction material had sheared completely off the clutch (clutch is only 9 months old). Mechanic said that this was extremely unusual.

As a precaution due to the shifting problems, decided to drop the gearbox out as well of see if there were any problems. Found the problems with the second gear cog/shaft and syncro's when they looked at the gearbox.

As per previous posting - the second gear is actually a gear as part of the shaft which also has the reverse gear on it. Price for this single piece was quoted as $1,500. Apparently the second gear teeth was chewed really well along with the second gear syncro being stuffed. Once again, not sure exactly how this would have happenned, but when I pick the car up, I will get the old parts back and should be able to post some photo's.

Mechanic was thinking that the initial clutch problem may have impacted/worn the syncro. Not real sure but the previous clutch failure was very dramatic. Clutchpedal just went to the floor and no more gears - car stopped in the infield of the track and got towed back to the pits. So I doubt that there was any impact from the first clutch failure.

I did not ask if there was any debris in the gearbox. If the damage was recent, and the teeth were chewed/worn, you would expect debris in the oil. This has never been a problem to date and gearbox oil was changed after Bathurst as a precaution - so I think it might have been there for an extended time, perhaps prior to me buying the car.

As this develops, I will post more information.

Short story, a freshen up of your gearbox will be a lot cheaper than losing second gear.

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[MC968CS]

Damn, thanks for posting, sounds a pain in the wallet and to the competition series.

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[flash]

this is something that i worry about now that i have so much more torque - we know that the gearbox design is a bit weak down low, which is exactly why it is not suited to a V8 - i am hoping that because the SC develops its torque in a more linear fashion, that it will spare it the failure, given that i already had the box redone

for the track toy, it will definitely get some improvements to strengthen things up

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[RS Barn]

Shearing the friction off clutch disc is common with DMF at track.
I just fixed another gearbox with a damaged 1st 2nd syncro hub. Customer tried a 5th to 3rd downshift and caught 1st for a second. This damaged hub and syncros. Symptom is difficulty getting in and out 1st and 2nd while running . A bit easier when car is shut off.

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[rhudeboye]

" Symptom is difficulty getting in and out 1st and 2nd while running . A bit easier when car is shut off."

Kinda sounds like my car Pete. The thing is, I recently had all my syncros replaced.

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[RS Barn]

When syncro hub is damaged it really takes some effort to get out of gear. like someones holding the other end of shift linkage

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[craigawoodman]

I have picked up the car. Looked at the 1st gear cog and it is worn on the engagement side for about 1/3". Syncro's replaced on 1st, 2nd, 3rd and 4th. First gear replaced, plus the second gear shaft assembly.

New flywheel and clutch is taking some getting used to.

I have the old clutch at home now, it has torn about 1/8th of the circumference off the friction material off. Pressue plate, etc is fine.

Bloody expensive problem. I cannot remember grabbing 1st gear anywhere. Not sure if it is just age of car (125,000km).

We are discussing more frequent gearbox oil changes as a possible help.

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