Second Gear Randomly Popping Out
03-06-2012, 12:31 PM
#17
Nordschleife Master
There are 14 different shims that go under 4th gear that vary by .05mm that are used to adjust the location of 2nd gear and set the stack height. My guess is that in the Getrag factory when they build these gearboxes they don't spend a whole lot of time measuring and checking this and use a standardized shim of the same size in pretty much every gearbox. Variances in width of individual gearsets themselves (which could be 3rd, 4th, or 2nd) can alter the whole stack and put the 2nd gear dog teeth just ever so slightly too far away from the 1/2 slider assembly. It's been an issue for 15 years...
03-06-2012, 12:45 PM
#18
Rennlist Member
What is the best guesstimate with respect to pp/clutch issues with the 3.8- too much power? Aren't the trannies for the 6 and 7 essentially the same other then then 3.8 has shorter gears.
03-06-2012, 12:59 PM
#19
Nordschleife Master
My head tends to be buried firmly inside of the gearbox. I am aware that there seem to be clutch/pp issues going on, but haven't really been looking at it too closely and haven't held a broken one in my hands at this point.
Yes, they are essentially the same gearbox other than ratio changes.
Yes, they are essentially the same gearbox other than ratio changes.
03-06-2012, 11:55 PM
#20
Rennlist Member
There are 14 different shims that go under 4th gear that vary by .05mm that are used to adjust the location of 2nd gear and set the stack height. My guess is that in the Getrag factory when they build these gearboxes they don't spend a whole lot of time measuring and checking this and use a standardized shim of the same size in pretty much every gearbox. Variances in width of individual gearsets themselves (which could be 3rd, 4th, or 2nd) can alter the whole stack and put the 2nd gear dog teeth just ever so slightly too far away from the 1/2 slider assembly. It's been an issue for 15 years...
For me, the problem is becoming increasingly frequent. These days I'm sure to get a "pop-out" with given these conditions: cold transmission+slight downhill+no/little throttle. I'm taking it into the dealer and gonna create a ruckus...
03-07-2012, 01:56 PM
#22
Nordschleife Master
If it's getting worse over time it's because the synchros are wearing and the engagement teeth are getting banged up. If the car was fine for 5k or 10k mile and then suddenly starts doing it, that's usually user error and not assembly error. People hate when I say that, but 2nd gear on these cars is not robust and does not take kindly to bad downshifts.
This is how your 3rd-6th engagement teeth look:
This is how they look on 2nd:
See the difference and how easy it could be to damage those teeth with a single ZING incident?
There is a real issue with tolerances on these gearboxes and a certain percentage of them not being built to proper spec from day one. But it's not epidemic like the questionable LSD in the gearbox. It's a small percentage of the production. Most of the people with 2nd gear pop out problems have caused them themselves.
This is how your 3rd-6th engagement teeth look:
This is how they look on 2nd:
See the difference and how easy it could be to damage those teeth with a single ZING incident?
There is a real issue with tolerances on these gearboxes and a certain percentage of them not being built to proper spec from day one. But it's not epidemic like the questionable LSD in the gearbox. It's a small percentage of the production. Most of the people with 2nd gear pop out problems have caused them themselves.
03-08-2012, 01:22 AM
#24
Rennlist Member
There is a real issue with tolerances on these gearboxes and a certain percentage of them not being built to proper spec from day one. But it's not epidemic like the questionable LSD in the gearbox. It's a small percentage of the production. Most of the people with 2nd gear pop out problems have caused them themselves.
03-08-2012, 02:22 PM
#25
Nordschleife Master
03-08-2012, 05:57 PM
#27
Nordschleife Master
I was brought up with the understanding that you never admit that you like to touch it. But sure, visitors are welcome. Some days get crazy here and I don't have much time to spare but other days I could spend an hour with someone just showing them stuff. Today is one of the former...
03-08-2012, 11:19 PM
#28
If it were the shifter cable, then it wouldn't just be second gear. It would be 4th and 6th as well to the best of my knowledge. When just second, then worn gear/synchros are likely to blame.
I love it when you pull out a bunch of shop pictures to illustrate your point. Thanks! For me this problem has been around since new (heck, the first popout was when I drove the car home from the dealership!!). But I take your point--with dogteeth that fine even the finest error can worsen the problem. But before I point fingers at the box itself, is there any chance this may be caused by a loose/mistuned shifter cable? I recently had my LSD replaced and obviously that required a tranny-out. The popping-out noticeably worsened after that LSD job.
03-09-2012, 10:40 PM
#29
John, if you're having Princeton Porsche do the repair, ask Gene about the white 2011 GT3 with the same 2nd gear pop-out issue brought in last year. Car only had a few hundred miles when the issue started -- turned out to be a bad synchro.
