Found possible root cause of many 915 shift problems

[wayner]

This is the first week I have had my car on the road after a many year restoration.

I'm not having fun. The shifting is worse than any 915 I have ever been in.
I am being gentle with it until I figure out what is up.

I have to double clutch to downshift or I get stuck between gears. Upshift take a painfully long time waiting for permission to engage.

I have the best of the best. Something is up.
-Fresh transmission
-Wevo internal shift gate in the tranny
-Wevo shifter and linkage
-new clutch and resurfaced flywheel.

Those are all the common areas and fixes that people recommend. I have them all.

The ONLY variable is that I forgot to replace the throwout bearing. (D'oh! I was not being cheap, just too many balls in the air and I forgot).

It might cause shifting issues. I suspect this because the bearing is making noise and sounds like it is bad. I wonder if it is keeping the input shaft spinning even slightly?

If my hunch is right, there may be a lot of drivers out there with balky 915s that do not require a rebuild to work better.

I will post more once the bearing has been replaced in this process of elimination.

[tirwin]

I recently had an issue where the ball cup housing at the end of the shift rod below the tower came loose. When I fixed it I had to readjust the gate shift a little and the alignment on the coupler in the rear tunnel. Not a lot. Just needed a little tweak. Result was a huge improvement in shift feel. Point is... Don't overlook the possibility that you may need to keep tweaking things until it improves. You introduced a lot of new variables.

[wayner]

You bring up an excellent point.
I am also wondering if I have an issue with the shifter mechanism since in 5th I hear a ringing (high frequency rattle) inside the shifter housing at the base of the shift lever.
I'll look for any possible adjustments.

Are you also using the WEVO components?

I'm all ears for suggestions.

[javadog]

Regarding the rattle in the shift housing, if you still have the original housing from 1973, you may need to re-bend the u-shaped parts that Porsche calls the shift lever bearings, to make them a slight interference fit in the housing, and with resepect to the lever. Or, you could replace the housing and bearing with a later one (77-on) as the bearing is a one piece design and the housing has an adjustment for preload on this part.

JR

[X JBM X]

Might be a stupid question, but have you replaced your coupler bushings and adjusted the coupler recently?

[Nickshu]

In my case it was worn out engine and transmission mounts. Installed new ones and shifting improved dramatically.

[wayner]

Just to recap everything from the shift knob back has been replaced

-New Wevo shifter and linkage
-New coupler
-Fresh transmission
-Wevo internal shift gate in the tranny
-Wevo engine mounts
-new clutch and resurfaced flywheel.

I may be able to gain something by adjusting, but I am not hitting other gears by accident. None of my gears work better than others.

Keep the suggestions coming though because I hope this thread will be useful to others.
Given that I know the bearing is sounding bad, as I see it, my current options are:
1) Replace the throwout bearing and start from there.
2) Check for any adjustment in the Wevo system after the new bearing is in.

I still suspect the throwout bearing is the culprit since it is making noise. It is the one component that I never see discussed when talking 915 shifting issues, so it will be interesting to see what affect it has on otherwise solid/fresh system.

[tirwin]

In my case it was worn out engine and transmission mounts. Installed new ones and shifting improved dramatically.

Another good point.

[tirwin]

Might be a stupid question, but have you replaced your coupler bushings and adjusted the coupler recently?

He's using the aftermarket Wevo coupler so it doesn't use the same bushings.

[tirwin]

You bring up an excellent point.

I am also wondering if I have an issue with the shifter mechanism since in 5th I hear a ringing (high frequency rattle) inside the shifter housing at the base of the shift lever.

I'll look for any possible adjustments.



Are you also using the WEVO components?



I'm all ears for suggestions.

My setup is stock except I added the Seine gate shift kit and Ed's shift coupler bushings.

My experience is that shifting improvements with the coupler adjustment is a trial and error process where slight adjustments can have noticeable changes.

The next time I drop the engine I'm going to replace the engine and tranny mounts and probably the ones from Rebel or Elephant.

[Josh D]

Are you certain the shift forks inside are adjusted correctly?

[ivangene]

who did the trans refresh?
coupler adjustment is important but I dont think that sounds like your issue

have you checked the conical screw under the shift tower that holds the metal cup onto the shift shaft that runs the length of the tunnel? - a loose one of those can provide a good bit of cussing and moaning

have someone else who has a wevo drive your car - I found it took me a while to acclimate to the wevo the first time - you might be just on the learning curve - I once got stuck in 5th on the freeway and had to stop on the side of the road to manually get it out - this was a friends car I drove around for a few weeks, and after about 2 weeks....I was much better - the car didnt need adjustments

so - think about that too

and post pics for goodness sakes!

[frannyB]

Any difference between hot and cold?

I had a bad throw-out bearing on an older Saab and it went all automatic on me and would want to creep with the clutch in so it is possible, but it did make a fair bit of noise.

I would like to improve my car's shifting (worse when warm) so I'm staying tuned in

Franny

[Matt Monson]

Refreshing a 915 with Rauch and Speigle synchros and/or not replacing sliders can leave a 915 shifting like a big rig...

[Peter Zimmermann]

To the OP, can you provide a parts list for the trans re-fresh? I fear that whoever did your trans installed new synchros, as Matt posted, but re-used the old sliders. This can cause a "fresh" 915 to shift very badly.

A noisy TOB usually cannot cause shifting issues, did you follow factory instructions regarding clutch adjustment? Did you check/replace your throw out bearing release fork - it can crack. Did you replace the clutch cable; if yes, is it o.e.?

[Targalid]

One thing not mentioned yet that I found dramatically affected my shifting was simply adjusting the clutch freeplay. You can't shift if the clutch is not fully released.

[Elombard]

I read once that the internal gate shift makes for a very precise mechanism that takes some getting used too. That said I am still not sure my wevo shifter is adjusted right after several years.

[wayner]

Lots of good ideas here.

My rebuild sheet is in one of the first few pages of my project thread in my signature ( along with lots of pics)

Saving a 73 from the crusher...

Wevo IS extremely precise and I agree about the learning curve. Having daid that, getting into gear is a challenge but getting out is more so.

I'll check the clutch free play. That is an excellent easy suggestion. The cable is new and may need adjusting after the first few miles.

I love the vast number of suggestions. Many haven't appeared in the other threads that I have come across.

[javadog]

Originally Posted by wayner

I'll check the clutch free play.

While you are at it, check the travel, as well.

JR

[Peter Zimmermann]

Originally Posted by javadog

While you are at it, check the travel, as well.

JR

Yes! If your car has an adjustable pedal stop for the clutch, try to move it a little to provide a bit more "throw."