GT4 G81 Transmission Failure
11-02-2016, 12:12 PM
#151
Nordschleife Master
If the gear is failing in that way—where it would (probably?) not were it splined—it seems more like it's a torque overcoming weld issue. In other words, such a failure seems to me like it happened when the 3.8's torque was applied in gear.
Matt, does that make sense?
Wonder if this is also an issue exacerbated by the GT4's stickier tires? The low mileage at failure in reported cases is disturbing.
Matt, does that make sense?
Wonder if this is also an issue exacerbated by the GT4's stickier tires? The low mileage at failure in reported cases is disturbing.
While all of what we've seen here is anecdotal, one thing that is consistent among the owners and shops that have spoken directly to me offline is that the failures have been happening on the upshift.
Lastly, while I have suggested that this may be a design issue, I think it important to point out that EB welding dog teeth like this isn't a questionable technology and has been reliably used for over 20 years on Getrag built gearboxes in Porsches. All 993 1st and 2nd, GT2/GT3 1st and 2nd and a variety of other gearboxes use this method. We use it on our replacement parts for the above gearboxes. As such, it may still be a "batch" issue and not the mismatched part and ratio idea I put forward above. We know what the failure is, but the cause of the failure is purely speculative.
11-02-2016, 01:25 PM
#152
Rennlist Member
This is a logical and reasonable idea. I wonder if the Audi TDis that use this same gearbox have also gone to a welded 3rd and if they also have seen any failures.
While all of what we've seen here is anecdotal, one thing that is consistent among the owners and shops that have spoken directly to me offline is that the failures have been happening on the upshift.
Lastly, while I have suggested that this may be a design issue, I think it important to point out that EB welding dog teeth like this isn't a questionable technology and has been reliably used for over 20 years on Getrag built gearboxes in Porsches. All 993 1st and 2nd, GT2/GT3 1st and 2nd and a variety of other gearboxes use this method. We use it on our replacement parts for the above gearboxes. As such, it may still be a "batch" issue and not the mismatched part and ratio idea I put forward above. We know what the failure is, but the cause of the failure is purely speculative.
While all of what we've seen here is anecdotal, one thing that is consistent among the owners and shops that have spoken directly to me offline is that the failures have been happening on the upshift.
Lastly, while I have suggested that this may be a design issue, I think it important to point out that EB welding dog teeth like this isn't a questionable technology and has been reliably used for over 20 years on Getrag built gearboxes in Porsches. All 993 1st and 2nd, GT2/GT3 1st and 2nd and a variety of other gearboxes use this method. We use it on our replacement parts for the above gearboxes. As such, it may still be a "batch" issue and not the mismatched part and ratio idea I put forward above. We know what the failure is, but the cause of the failure is purely speculative.
Best advice remains to drive the car. I wasn't polite with the throttle in third last night...
11-02-2016, 09:53 PM
#153
Post #98
"I used to own a welding supply business in another life. A weld with full penetration is stronger than the base metal.Could be nothing more than a batch of bad welds. Machine settings and amperage settings that changed which would affect penetration and strength". carl
"I used to own a welding supply business in another life. A weld with full penetration is stronger than the base metal.Could be nothing more than a batch of bad welds. Machine settings and amperage settings that changed which would affect penetration and strength". carl
11-02-2016, 10:31 PM
#154
Nordschleife Master
Post #98
"I used to own a welding supply business in another life. A weld with full penetration is stronger than the base metal.Could be nothing more than a batch of bad welds. Machine settings and amperage settings that changed which would affect penetration and strength". carl
"I used to own a welding supply business in another life. A weld with full penetration is stronger than the base metal.Could be nothing more than a batch of bad welds. Machine settings and amperage settings that changed which would affect penetration and strength". carl
11-03-2016, 01:54 AM
#155
I know it's fusion welding with no filler material. It is still dependent on full penatratiion getting the two materials into a full molten state to melt into one . That's what welding is ..
"Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact."
"Electron beam welding (EBW) is a fusion welding process in which a beam of high-velocity electrons is applied to two materials to be joined. The workpieces melt and flow together as the kinetic energy of the electrons is transformed into heat upon impact."
11-04-2016, 12:37 PM
#158
Burning Brakes
AFAIK, the 991R gearbox is based on the 7-speed standard-911 box, with top gear either removed or disabled. I don't think they're the same as the Cayman/Boxster units, although they might share some common parts.
11-04-2016, 12:40 PM
#159
Racer
They looked in the computer and it appeared to be the same with a different diff # The guy said we only have one 6 speed... same in all cars on the floor.
11-04-2016, 04:30 PM
#161
Nordschleife Master
Nope. If we were talking the PDK there's some parts commonality between the cars. But in manual gearboxes the mid-engine and rear engine gearboxes don't even come from the same manufacturer. Boxster and Cayman gearboxes are made by Getrag. Carrera gearboxes are from Aisin.
11-05-2016, 05:28 PM
#165
Rennlist Member
Congratulations on using your car. 
I plan to drive mine and let the CPO be my ride along mechanic for the next 5 years and 1 month.
I plan to drive mine and let the CPO be my ride along mechanic for the next 5 years and 1 month.