I've posted some questions about this in the past, but I think this is probably a better description.
I have a '72 915. My problem seems to be quite unique, or at least I can't seem to find anyone else talking about it. The guide piece on the 3-4 shift rod (I'm not sure exactly what it's called, but it is the iron part bolted on next to the brass fork) rotates down so that the selector arm (with the ball end) gets caught on on it. When in nuetral, this prevents the shift selector rod (where the linkage connects to) from being able to rotate far enough to the drivers side so that the tab on this rod can engage the notch in the 5-R shift rod. In this state, I get 1 through 4 but no 5-R.
A little history. Back in Sept '06 the tranny got stuck in two gears while at Road America. A local Porsche wrench pulled the inspection cover and freed it up using a big screwdriver, and the rest of the weekend it was fine. This past May, I was back at Road America and I first experience the above problem, i.e., loss of 5-R. I pulled the tranny, discovered the problem, used a pry bar through the inspection hole to rotate the guide piece on the 3-4 rod back up, and the tranny worked fine...for a while. I was at Road America again in September and the problem reoccurred after a couple of sessions (maybe I should stick to short tracks where I don't need 5th!). The season was done so I just parked the car until after the holidays.
I got the tranny out and back on the engine stand last night (In the process I managed to snap the speedo drive off the front cover
, so if you happen to have a front cover you'd like to sell me, let me know!) Sure enough, the exact same thing has occurred, the 3-4 guide has rotated creating about a 4-5mm gap btween it and the similar guide on the 1-2 rod. At this point, one should probably ask why does this happen? My theory is that it can be traced back to the Sept '06 "stuck in two gears" episode. This itself was possibly caused by a worn shift coupler (since replaced) and driver error (as hard as that is to admit). When the mechanic went in there with a screw driver to un jam it, he may have effectively loosened this guide on the 3-4 rod. Repeated hard use, with the ball end of the lever pressing back and forth on this guide, caused it to rotate slightly, just enough that the ball on the lever now catches on the base of the guide.
I realize now that simply pushing it back into alignment is not a permanent solution. To me, it would seem that I need to re-torque the bolt holding this guide on the 3-4 rod to prevent it from rotating. Since the bolt is on top, I have to pull the main case off to get at it.
1. Is there anyone out there who has experience anything like this before? If so, how did you resolve it?
2. Also, is there an "official spec" as to the gap/clearance between the two iron guides on the 1-2 and 3-4 shift rods? I know 4-5mm is too much, since the ball end won't pass through when in nuetral, but I don't know how close they should be?
I appreciate anything anyone can share with respect to this issue.
Thanks.
Roger
Note: I should probably mention that I had the tranny rebuilt in 2002 and it has only seen a few thousand miles since the rebuild. I must say, it looks pretty good inside from what I have seen. I'll know more once I pull the main case. It shifts great with no other issues than the above.