I posted last year about difficulties pulling the shifter out of gear when decelerating. This was mainly with 3rd although it did happen with other gears. It was suggested that it could be clutch, corroded splines or even gearbox problems. I thought I would try a few of the easier and cheaper solutions first. I bled the clutch slave cylinder with no luck. I then changed the gearbox oil to Amsoil and then Redline with no luck. This winter I replaced the clutch slave cylinder and hose for $130 and gave the system a good flush in the process. There was a ton of crap in the brake fluid which I'm guessing were from deteriorated hose and seals. I finally got the car on the road last week. Oddly enough, for the first 20 or 30 miles the problem still existed. Now I have put another 60 or 70 miles on and the problem is no longer. I'm scratching my head as to why the change wasn't immediate. I'm just glad it's fixed and now I can think about that Golden Rod shift rod upgrade!

 

Matt,
Your brake fluid may have been original to the car.....

I'm glad to hear you've solved the mystery!


Andreas

 

Timely! I hope this is a possible fix for me as well.

Question; When you experienced the issue, would a "blip" of the throttle enable/smooth the shift? I have this problem and blipping cures it. Still, it makes me wonder what is wrong and I sure would like it gone.

What brand of gear oil for the trans did you settle on? And did you use 75W90 in each case? I happened upon some of Robin's writings on this general topic a few days ago:
http://p-car.com/diy/transmissionfluid/

Do you think the problem was related to ambient temps?

 

FWIW, I drain & refill my tranny each winter, and use 75W/90 Mobil1 Delvac (formerly known as Mobilube SHC). The transmission shifts perfectly with absolutely no complaints.


Andreas

 

The car shifted very nicely except for the deceleration problem. It would be hard to pull out of gear. If I depressed the clutch you could see the rpm's hang for a second before falling then everything was fine. A quick blip would also help. I don't believe ambient temps were an issue either as the problem didn't change with the gearbox fully warmed. This was a consistent problem and it didn't come and go.

I tried the Amsoil gear oil and then the Redline 75W90NS with no real differences. The gear oil is just not the problem as it shifts fine. I almost bought 20 litres of the Mobil Delvac but quit chasing my tale. The clutch slave and hose were actually cheaper than the pail of Delvac! You can't buy that stuff around here in one litre or even one gallon jugs.

 

I would probably run Delvac if I could get it per my last post. The gearbox oil should last a very very long time unless you spend time on the track.

 

Agree. But I sleep better knowing what the drain plug magnet looks like after a year of fun! Besides, I have the car on stands each winter - draining and refilling the tranny takes all of 15 minutes.

I use the same neurotic rationalization with my brake/clutch fluid and flush it annually as well.


Andreas

 

I'll probably do the brake fluid every year as that is cheap and easy and might save spending $$$$ in the long run. Fortunately or unfortunately, I have not been able to find Xenit in Canada as I'm looking for another pastime for next winter and I should have my 4 post lift by then.

 

Funny, I am also experiencing some resistance in the shifter when gearing down. Blipping the throttle does make disengaging smoother. I also changed the gear oil but used what the dealer recommended. I think it was a Swepco product.

If Matt's problem disappear after sometime, could it be the gear oil changing viscosity? Mongrelcat, when did you discover the problem, was it also after a gear oil change?

Anthony

 

My understanding is that the sludge/waxy buildup/white residue & crystals in the brake fluid of the 1995 & 1996 993 cars may have originated from faulty brake fluid filled at the factory. A few Porsche techs at the local dealerships believe Porsche should have recalled the cars affected. This issue is well-documented on the PCA tech forum.

If the system was not thoroughly flushed in the early years, the sludge/residue can clog the very narrow ABS pump channels and cause a soft brake pedal. New ABS pumps from Porsche are $2,000. The pumps can be flushed out using a procedure involving activating all the ABS valves & channels while using high pressure flush techniques.

 

The symptoms suggest that the clutch plate is still in partial contact when declutching: this makes the syncros do triple duty on gear changes, especially on down shifts .... and is why 'blipping' the throttle appears to help, for that action 'syncros' the gearbox as the clutch plate is still in contact: otherwise, the gearbox would not respond to any engine speed change, n'est ce pas?.
( a true double clutch action [ momentarily engaging the clutch in neutral between gear changes] will cause the trans internals to speed up for 'non-syncro' gear changes ... only because the box & engine are connected).

The two prime causes of clutches not fully disengaging have already been well noted - clutch plate dragging on the input shaft splines, or an inadequate stroke from the slave cyl. A seizing pilot bearing can also similar issues, but is relatively rare AFAIK.

Yes, gearbox lubes can also influence shift quality .... but the blipping on downshift with clutch depressed suggests to me that it is a plate not fully released - at least it is an opinion

 

I've had the problem since day one, but that was only 6 weeks ago when I bought the car at 101k miles. PO never mentioned it. Gear oil was last changed 30k miles ago with M1 75w90. I look at it as a good reason to practice blipping a lot, until I can figure it out.

I mentioned the issue in another thread and someone pointed me to previous threads on the problem. Here's one:

https://rennlist.com/forums/964-foru...t-of-gear.html

 

In my experience, clutch hydraulics have been one of the most ignored aspects of 993 ownership.

People will religiously maintain their brakes with annual flushes, but the clutch system gets either forgotten or ignored and this results in accelerated transmission wear as Garth wrote.

Kudos goes to Andreas who does the job right with annual brake & clutch flushes as this can save big money in parts and repairs over the long term. Brake fluid is far cheaper than replacing clutch parts, much less a transmission overhaul.

 

+1 and if Andreas ever sells that car, the buyer will be aquiring an almost new 993.
I know of some 993s cared for as well, none cared for better.

 

True. As I mentioned earlier, the state of the fluid drained out of my slave cylinder was horrid. Even ancient brake fluid never looks like this stuff.