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GT4 G81 Transmission Failure

Old 09-19-2016, 12:17 PM
  #1  
Mgkuehn
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Default GT4 G81 Transmission Failure

G81/20 3rd gear AWOL. Circumstances: Brake hard for turn and downshift to 3rd, turn in, back on gas, lift, tap brake for next turn in, turn in, gas and no 3rd gear. Failure must have occurred when I lifted to brake. Absolutely No Warning[/U], no shift issues, no noise, grinding etc., no warning lights, nada. Car was performing flawlessly.

When attempting to shift into 3rd nothing happens, it felt like the gear did not select. The shift indicator will say 1 and sometime 5. When setting still shifter feels normal, under load feels light into 3rd. All other gears work normally and a check of the DME says no error codes found. I did not get any ‘check engine’ warnings and am running Michelin Cup 2s. Failure is at 4500 miles and about 13 track days.

Diagnosis by Porsche: Techs think it’s the neutral position sensor. Indications are that sensor is not communicating as it should. No part in the US, being shipped from Germany and won’t be here until next week.

About three days after diagnosis Porsche called and said assume you are tracking the car. Ans. Yes - they should know since they have done two track inspections for me. Then asked two questions.
(1.) Have you gotten any “check engine” warning lights. Ans: No
(2.) What tires have you been running? Ans: Michelin Cup 2s/OE size. No other tires have been on the car. Service Manager seemed a little nervous about asking the question. (In the owners guide for track usage it says not to run slicks.)

Two days after asking about the tires, Porsche called me and said they were going to replace the entire transmission. Hate to be a pessimist but….. Seems to be a sudden reversal after asking about the tires. Awaiting new transmission arrival. Hope to find out what the real issue was after the failed transmission is pulled. Standby for additional information.
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Old 09-19-2016, 12:31 PM
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Sucks man.. Thankful you shared the experience. & Hoping you get this resolved asap.

Sub'd
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Old 09-19-2016, 12:32 PM
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There have been numerous people receiving new transmissions from Porsche (including me) for various failures. Porsche won't allow the dealer to take the transmission apart so just issues a brand new one. I think this is a good move as they themselves can inspect the failed transmission and the customer gets piece of mind with a new one. Some cars have been tracked and some have not. I wonder what the issues are with these transmissions? It may not be robust enough.
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Old 09-19-2016, 12:46 PM
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Me thinks there is something a bit doggy with the syncomesh.
I also got a crunch even when the clutch was hard to the floor.
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Old 09-19-2016, 01:30 PM
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Originally Posted by kyrocks View Post
There have been numerous people receiving new transmissions from Porsche (including me) for various failures. Porsche won't allow the dealer to take the transmission apart so just issues a brand new one. I think this is a good move as they themselves can inspect the failed transmission and the customer gets piece of mind with a new one. Some cars have been tracked and some have not. I wonder what the issues are with these transmissions? It may not be robust enough.
A recent case: https://rennlist.com/forums/gt4/9540...placement.html
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Old 09-19-2016, 01:55 PM
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Ugh, this is really disheartening to see, especially if the diffs give up as early as has been suggested and people start turning to Guard diffs as a solution, because that could potentially result in a denied warranty claim for a gearbox that failed later since the diff resides in the transmission housing.

OP, I'm betting they were nervous asking you about tires because Porsche had told them to ask whether you ran slicks and that they might deny the claim if you had, and the dealer didn't want to be the one to pass that news along. Glad you're being taken care of.

I too very occasionally heard a grinding noise even with the clutch fully down, though I can't remember the last time it happened. My car has a little over 6K miles on it now.
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Old 09-19-2016, 01:55 PM
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Originally Posted by kyrocks View Post
It may not be robust enough.
Interestingly, these transmissions have proven to be very durable in the past Caymans... including racing and aftermarket turbo'd cars.

It does seem, for the small sample size of these cars... there are more failures than should be.

Originally Posted by jphughan View Post
I too very occasionally heard a grinding noise even with the clutch fully down, though I can't remember the last time it happened. My car has a little over 6K miles on it now.
Several have posted up about grinding, but I can't think of a single time that I have heard it... and I'm at 7k miles. Makes me wonder if there was a batc hof synchros or something... and some cars have the issue, some don't.
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Old 09-19-2016, 01:57 PM
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Out of curiosity, have the people seeing transmission failures swapped their gearbox oil, even if they stuck with PTX? I know that these gearboxes have been around a while and various owners have run lots of different oils, but this might still be an interesting data point. Or maybe the oil is fine and the people seeing problems had a shop that over/under-filled the gearbox during the service? From what I've read so far, the advice seems to be just keep filling it until oil runs out of the fill hole, but I haven't seen that on an official document specific to this gearbox, only documentation for past Caymans, and some other docs said to stop a certain level below the fill hole or fill it to overflowing, then wait for the fluid to settle, then top off to a specific point. It would be nice to have official fill level guidance for this specific transmission.
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Old 09-19-2016, 02:48 PM
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Interesting to see how this manifests itself.

My experience from GT3 transmissions: Change oil frequently and often. I do my RS with every OCI, which is every 5 track days. Excessive? $100 in oil vs. $5k+ tranny/rebuild.
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Old 09-19-2016, 04:12 PM
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Mine was replaced at about 3000 miles.
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Old 09-19-2016, 05:56 PM
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Originally Posted by kyrocks View Post
Mine was replaced at about 3000 miles.
Same issue? Same gear?
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Old 09-19-2016, 06:01 PM
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Originally Posted by Spyerx View Post
Interesting to see how this manifests itself.

My experience from GT3 transmissions: Change oil frequently and often. I do my RS with every OCI, which is every 5 track days. Excessive? $100 in oil vs. $5k+ tranny/rebuild.
NF, but your RS doesn't count.

So far no other fluid other than OEM has been officially identified on the GT4. Not everybody has the DIY capability; dealer hour / labor charges in addition won't make it as cheap as you have posted.
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Old 09-19-2016, 06:41 PM
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This doesn't sound like 3rd gear failed. This sounds like something in the internal shift assembly failed. A failed gear would have been a nightmare crunch and might have put a whole in the case. If you suddenly can't find the gear its not shifting into the gear. Could be as simple as a roll pin being forgotten in assembly or a bolt not tightened properly and something slipping. I don't think the sky is falling. This doesn't suggest a trend to me. My focus comment about various reasons is important. This isn't like the 996 turbo 22nd gear pop out where everyone in large quantities all had the same exact problem.
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Old 09-19-2016, 09:22 PM
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Originally Posted by ExMB View Post
NF, but your RS doesn't count.

So far no other fluid other than OEM has been officially identified on the GT4. Not everybody has the DIY capability; dealer hour / labor charges in addition won't make it as cheap as you have posted.
BS. I stated change fluid often. I didn't state what to use. You follow the factory intervals and track the car... good luck
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Old 09-20-2016, 01:59 AM
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Originally Posted by Mgkuehn View Post
G81/20 3rd gear AWOL. Circumstances: Brake hard for turn and downshift to 3rd, turn in, back on gas, lift, tap brake for next turn in, turn in, gas and no 3rd gear. Failure must have occurred when I lifted to brake. Absolutely No Warning[/U], no shift issues, no noise, grinding etc., no warning lights, nada. Car was performing flawlessly.

When attempting to shift into 3rd nothing happens, it felt like the gear did not select. The shift indicator will say 1 and sometime 5. When setting still shifter feels normal, under load feels light into 3rd. All other gears work normally and a check of the DME says no error codes found. I did not get any ‘check engine’ warnings and am running Michelin Cup 2s. Failure is at 4500 miles and about 13 track days.

Diagnosis by Porsche: Techs think it’s the neutral position sensor. Indications are that sensor is not communicating as it should. No part in the US, being shipped from Germany and won’t be here until next week.

About three days after diagnosis Porsche called and said assume you are tracking the car. Ans. Yes - they should know since they have done two track inspections for me. Then asked two questions.
(1.) Have you gotten any “check engine” warning lights. Ans: No
(2.) What tires have you been running? Ans: Michelin Cup 2s/OE size. No other tires have been on the car. Service Manager seemed a little nervous about asking the question. (In the owners guide for track usage it says not to run slicks.)

Two days after asking about the tires, Porsche called me and said they were going to replace the entire transmission. Hate to be a pessimist but….. Seems to be a sudden reversal after asking about the tires. Awaiting new transmission arrival. Hope to find out what the real issue was after the failed transmission is pulled. Standby for additional information.
Hello, I've been reading posts on rennlist for a while but have never been registered. It is now done . The reason is I had the exact same experience yesterday on my third track day.
My GT4 was delivered in June, has 7600kms, with only 400kms of track use. Exiting a left turn in 3rd gear and reaccelerating, I lost the third and had to quickly engage 4th. No noise, no initial grind, no nothing. Until yesterday, gearbox was perfect.
The car went directly to the dealership and they checked it immediately. They didn't give me a diagnose but told me they are also changing the entire gearbox. They know I was on track and that the car was stock.
They didn't ask me any question and visibly just want to fix the problem as quickly as possible. Thumbs up for the service I should say.

On the other side, I'm a bit concerned about such an early and major failure... Is the car really intended for repetitive track days, for many years?
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