shifting mystery

kwc98 · 09-13-2008, 05:02 AM

I have replaced all of the shift coupler bushings and the cup bushing under the shifter and my shifting has improved immensely, however I now have the following symptoms that I would like some advice/direction:

1. shifting from 1st-2nd can be an adventure, somewhat balky at times, however 3rd-2nd is never a problem, it downshifts quite smoothly, just like I want 1st-2nd to be.

2. while driving the shift pattern will change, such as going into 3rd gear where 5th gear used to be! and just yesterday the opposite happened, instead of 1st gear being upper left, 3rd gear was there! I realize that this could lead to a serious mis-shift, from 4th to 3rd instead of 5th for example.

if you have suggestions, I would really appreciate it, thanks,
Ken

Porsche_monkey · 09-13-2008, 05:57 AM

How many miles on the tranny? The 1-2 balky shift is likely a synchro, pretty common on a 915.

Could your shift linkage be slipping radially on the clamped section? That seems likely from your description. 1-3-5 would move around if that happened.

Time for our resident tranny and apple polisher 'Dentist90' to chime in...

Oh Haha · 09-13-2008, 05:59 AM

Check the bolt/nut on the shifter rod clamp where it attaches to the shift coupler. There are easily stripped ot just get old and loose some clamping force. I replaced the bolt/nut combo with an Allen head bolt and found it easier to get good torque when tightening.

If it is loose, it will allow the entire rod to move on the coupler.

While you are in there, check the set screw on the coupler as well.

kwc98 · 09-13-2008, 03:34 PM

There was a little lateral movement in the coupler. I am surprised, since I would have thought the 1st to 2nd shift would move the coupler if it was loose. That part of the mystery solved.

Now, how does the transmission know to shift smoothly from 3rd-2nd but not from 1st to 2nd? I know nothing about transmissions, so this may be obvious to some, but not to me. Is there a logical reason for this?

thanks,
Ken

Flieger · Flieger's Garage

Did you get the ring shaped shift rod bushing in the tunnel behind the shifter.

Bushing replacement also usually necessitates coupler re-indexing.

richde · 09-14-2008, 12:55 AM

Quote:

Originally Posted by kwc98

There was a little lateral movement in the coupler. I am surprised, since I would have thought the 1st to 2nd shift would move the coupler if it was loose. That part of the mystery solved.

Now, how does the transmission know to shift smoothly from 3rd-2nd but not from 1st to 2nd? I know nothing about transmissions, so this may be obvious to some, but not to me. Is there a logical reason for this?

thanks,
Ken

Do you mean it's always balky, or that it takes a second or so to be able to engage 2nd from 1st?

kwc98 · 09-14-2008, 03:41 AM

Flieger :
The rod bushing was replaced.

richde:

I would say that 50% of the time, the shift from 1st-2nd takes a little extra effort. If the engine is torqued then it is usually worse. It seems like it will not fully engage and needs an extra pull, sometimes a little extra clutch. There is never any grinding. Now the shift from 3rd-2nd drops right in, one pull and good to go.