GT4 G81 Transmission Failure
09-20-2016, 02:26 AM
#16
Rennlist Member
Valid concerns. This trans is not Motorsport derived.... so who knows. I'd like to think it is up to the task!!!
09-20-2016, 03:54 PM
#18
Nordschleife Master
I've spoken to Mooty. He's going to help us figure out exactly what this failure is, and potentially why. I repeat that I don't consider this a 3rd gear failure. It is an internal shift mechanism issue that manifests with the inability to find 3rd. 3rd is still there and likely undamaged. Something is slipping or breaking in the mechanism and we'll figure out what it is. A pattern does appear to be emerging, unfortunately.
To me it has to be an assembly issue or a single defective part on this batch. This gearbox in several forms has existed for over a dozen years. It is a robust gearbox. There's nothing special or different about its use in the GT4. Your cars don't stress it more than the BGB Lunatic we ran at the 24 Hours of Daytona and won the GX Rolex series with.
09-20-2016, 05:12 PM
#19
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GT4 Transmission Failure Update
Transmission is in the car and it should be ready tomorrow. Found out the following:
• When the car was up on the lift and with the engine running they could hear noise from the transmission. He said it sounded like something was rotating (free spinning) and trying to shift. This sound was not audible on the street.
• Drained the fluid and checked for metal bits, pieces etc. The fluid was clear, no debris.
• The transmission will go back to Germany for tear down. Will try and get some feed back
• I am not the first to have a problem with 3rd gear. There is a car in Atlanta that has the same 3rd gear problem. The difference is that it is heavily modified and the owner was running on slicks. Don't have information on what mods were on the car, mileage or number of track days. That transmission is being replaced as well. So there now appears to be at least three or four trans failures.
From another Porsche source: this is a rare issue. However, he did say it is not a design fault and implied the fault lies with assembly quality.
• When the car was up on the lift and with the engine running they could hear noise from the transmission. He said it sounded like something was rotating (free spinning) and trying to shift. This sound was not audible on the street.
• Drained the fluid and checked for metal bits, pieces etc. The fluid was clear, no debris.
• The transmission will go back to Germany for tear down. Will try and get some feed back
• I am not the first to have a problem with 3rd gear. There is a car in Atlanta that has the same 3rd gear problem. The difference is that it is heavily modified and the owner was running on slicks. Don't have information on what mods were on the car, mileage or number of track days. That transmission is being replaced as well. So there now appears to be at least three or four trans failures.
From another Porsche source: this is a rare issue. However, he did say it is not a design fault and implied the fault lies with assembly quality.
09-21-2016, 12:20 AM
#21
Subscribed. Getting grind going from 4th into 3rd on reasonably high speed downshifts on track. Have been focusing on having the clutch all the way in, so it's not that. Using sport mode. Feels like it's not sync'ing all the way. Just put in a Dimple magnetic drain plug to see what's happening when the trans. fluid gets changed. 4,100mi. 18 sessions. No mods, other than 1.8deg. F. camber. Has been going on for the last 4 sessions.
09-21-2016, 02:51 AM
#23
Rennlist Member
18 sessions or 18 track days?
Matt assume you mean every 6 or so DE days ? (5-600 miles)
Matt assume you mean every 6 or so DE days ? (5-600 miles)
09-21-2016, 11:35 AM
#25
Drifting
Hmm, elsewhere I've seen you say change every half dozen weekends, i.e. 12 track days. 18 sessions with most DE organizers is only ~4 track days.
09-21-2016, 01:46 PM
#26
Nordschleife Master
Sorry, I think we have a misunderstanding on terms and the fault lies with me. When I was posting last night I took "session" as a complete DE event weekend. My guidelines haven't changed.
09-21-2016, 04:56 PM
#27
Rennlist Member
If there is such a thing as a "bad batch" of something - would it be reasonable to assume that if would affect a certain range of VIN number? I realize we wouldn't know how big the batch (or batches) might be, and when the first or last bad component went into the builds....but if we gathered the VIN numbers from cars affected by transmission problems - is it reasonable to think that if a VIN falls in between the confirmed "problem" cars, that there is a decent chance that car may also be affected by the bad component?
I'm curious about this as it relates to the transmission problems and also the parking brake malfunctions.
I'm just thinking out loud and hoping someone with experience or background in car manufacturing could provide and educated opinion.
I'm curious about this as it relates to the transmission problems and also the parking brake malfunctions.
I'm just thinking out loud and hoping someone with experience or background in car manufacturing could provide and educated opinion.
09-21-2016, 10:23 PM
#28
Nordschleife Master
If there is such a thing as a "bad batch" of something - would it be reasonable to assume that if would affect a certain range of VIN number? I realize we wouldn't know how big the batch (or batches) might be, and when the first or last bad component went into the builds....but if we gathered the VIN numbers from cars affected by transmission problems - is it reasonable to think that if a VIN falls in between the confirmed "problem" cars, that there is a decent chance that car may also be affected by the bad component?
I'm curious about this as it relates to the transmission problems and also the parking brake malfunctions.
I'm just thinking out loud and hoping someone with experience or background in car manufacturing could provide and educated opinion.
I'm curious about this as it relates to the transmission problems and also the parking brake malfunctions.
I'm just thinking out loud and hoping someone with experience or background in car manufacturing could provide and educated opinion.
Furthermore what if only 10% of the batch of parts is bad? Do they recall every car with a gearbox with the part from that batch. Or, do the bean counters say its cheaper to keep it quiet, repair and warranty as needed and have the math say it costs them less money and bad pr to skip the recall.
09-21-2016, 10:43 PM
#29
Rennlist Member
It's far more refined than just a vin. There are literally thousands of these gearboxes that came from Getrag. They are in crates and not really in a particular order though each has a serial number. As they go in cars their bar code is scanned. The vin on the car is linked to a serial number. The cars are not built in vin order. Only if Porsche gets with Getrag and identifies the source can they then identify a serial number range for gearboxes and issue device bulletins to gt4 and 981 owners with bad boxes. This is if the bad part is even tracked.
Furthermore what if only 10% of the batch of parts is bad? Do they recall every car with a gearbox with the part from that batch. Or, do the bean counters say its cheaper to keep it quiet, repair and warranty as needed and have the math say it costs them less money and bad pr to skip the recall.
Furthermore what if only 10% of the batch of parts is bad? Do they recall every car with a gearbox with the part from that batch. Or, do the bean counters say its cheaper to keep it quiet, repair and warranty as needed and have the math say it costs them less money and bad pr to skip the recall.
