Found possible root cause of many 915 shift problems
 

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.

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.

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.

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

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

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

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.

Another good point.

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

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.

Are you certain the shift forks inside are adjusted correctly?

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! ;)

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

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

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.?

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.

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.

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)

http://forums.pelicanparts.com/porsche-911-technical-forum/626050-saving-73-crusher-4.html

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.

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."

Good suggestions

I'll report back.

I'd only add that the static fork bolted by four nuts to the plate you can remove from the bottom of the 915 does get loose. Remove the plate, clean it up, loctite, and new gasket. I am sure tho that whoever rebuilt the trans must have seen to this as well.

This is an often-overlooked issue with the trans. Worth inspecting at your fluid change intervals.

Here is my update on this shifting issue so far:

Anyone following this thread knows now that everything is new front to back except for the throwout bearing. That bearing may or may not be significant to my problem though.

I drove the car to work one day adn got caught in stop and go traffic and detours. I probably spent 1.5hrs of clutch in clutch out creeping along. I also spent about an hour total to and from being able to use most of the gears, although double clutching up and down.

I parked it after that. All sorts of fears raced through my mind such as "did I forget to fill the new transmission (shifting was THAT bad).

After pouting for a few days and letting the car sit, I drove it to Chris Kirby's (My mechanic, the guy I trust anytime I need to call in an expert in my area).

The funny thing is that on the day that I drove it to his place, it shifted like a formula car!
(I've driven a formula car and my 911 may have even been better).

The question is WHY is it better?
I didn't do anything to it?

Chris drove it and he said it shifts fine.

I'm wondering: Break-in period perhaps?

That's the craziest thing I ever heard (well maybe not the craziest...)

Break-in period is the only thing I can think of, but it doesn't explain why it would shift better after sitting for a few days, when it shifted terribly right beforehand.

You did not mention whether or not you replaced the pilot bearing..I have seen a few where the PILOT bearing in the flywheel was not replaced and they would get sticky/not turn very well- consequently, the input shaft is still spinning at a slightly higher rate of speed than it should be. Given that you didn;t replace the t/o bearing, i would be questioning the pilot as well. May not be your issue but from what you are describing, it is certainly a possibility...

Was not 100% clear from your description though- do you have physical difficulty/stiffness engaging every gear, or is the actuation smooth but it grinds in all gears? Also, do the gear sets engage smoothly with the engine OFF?

Regarding CRAZY - On the way home on that day downtown, it may have been shifting better than at the beginning. THe next time after it sitting was when I noticed it though. My guess is that it got incrementally better throughout that day and I didn't clue in until the next drive.

Regarding the throw out bearing, no I have still not replaced it.

Regarding shifting, it would grind if I wasn't careful (mainly 1st) but terribly stiff everywhere, even shifting out of gears. It seemed that double clutching when going up a gear let it enter the next gear without wrestling with the lever as much. Double clutching downshifting ( and rev matching) was a necessity. Stiffness was not as noticeable without the engine running.

The transmission was rebuilt by a shop when the previous owner had the car apart. I am the first one to use the transmission since.

I'm not sure which bearings specifically were replaced. Here is the parts list he gave me in the book of receipts that came with the car.

SETH you may be on to something.
I suspect that the pilot bearing in the flywheel may not have been changed. I know that I didn't think to do it.

http://forums.pelicanparts.com/uploa...1315060818.jpg

I should also add ( for those who haven't followed my build thread) that this is the first time in 12 years that this engine and fresh ( 12 year old) transmission have been run since the restoration began 2 owners ago. I don't know if that adds anything to the diagnosis

I think its time to change the oil, Swepco for a 915
Right?

Kendall

http://www.pelicanparts.com/catalog/images/misc/LSD.jpg


http://www.pelicanparts.com/More_Info/KEN-LSD-7745.htm?Kendall%2080W-90%20GL-5%20Gear%20Oil%20With%20LSD%20Additive%20(1%20Quar t)

I agree with changing the fluid after putting a few miles on a fresh transmission, and who knows what fluid was used when it was rebuilt, but would fresh fluid in a fresh transmission go bad from sitting on a shelf for 12 years?

I don't know

It's at my mechanics now to take care of carbs etc. he says it now shifts fine without having done anything.

Strange. Maybe a pilot bearing not working well after years of sitting? Maybe it freed up after some miles?

Next winter when I drop the engine I will replace the throw out and plot bearings as a precaution

Another clue:

When I brought the car home the weather up in Canada was unseasonably cold.

It has been much warmer since. I wonder if this had anything to do with the dramatic difference in shifting? (my drives were short)

The fluid has been changed to whatever my many years of experience 911 technician uses, and it shifts well all the time. No adjustments have been made, just driving time and then later a fluid change.

(BTW, he said it shifted well when I brought it to him before he changed the fluid, but he kept it in a heated garage and the weather had warmed up. No idea what fluid was originally in it when I got it).

Just changed motors and found my throw out bearing to be toast even tho it only had about 35k on it.
Shifting was bit dodgy and it did cause a metallic whirring/clicking noise in the tranny that seemed to be at the shifter...I could diminish the noise by moving the shifter forward/back a tad while in gear.
When we pulled the tranny it was obviously the culprit. The clutch/basket/flywheel were in great shape. Bad bearing.
Replaced and shifts as new.

Thanks!

I'm suspecting that the drag caused by the other oil when cold was part of the issue. It certainly improved:
1) when warm and
now is consistently better with
2) the replacement oil.

It has never been as bad as it was when I first brought it home.


I still haven't ruled out a bearing issue. Next spring I will be able to make the observation once the new ones go in. (throw-out and pilot bearing for good measure).


P.S.
As a sidenote, I replaced the manual my transmission oil in my truck with the same grade that it came with, but royal purple brand synthetic, and it went from shifting like butter to barely shifting when the winter months came. After I went back to the brand the manufacturer recommended, all was good again but my synchros were worn from all that heavy handed shifting. There might be something to staying with dino oil when cold (which goes against everything I've been told about synthetic). I hadn't considered that this might be the issue with my 911 too.

Wayner,
Some trannies require a certain amount of friction to operate properly and some synthetics are way too slick.

Why do they get better when they are warm? Very puzzling