Defining Normal - The 915 Transmission

[mgar88]

I purchased my first air cooled 911 about 9 months ago. Having spent about 2000 miles behind the wheel (who really knows with a broken ODO), I still struggle to connect with the car on most days. Never before has it taken me this long to "learn" a car. There are good days where the engine sings and my shifts are seamless, and then there are other days where my sycros crunch and driving becomes more of a stresser than a stress-reliever. I'd like to think that driving my 911 is like practicing a musical instrument, but I get frustrated that I can't do a killer guitar solo yet.

For me, the largest learning curve is the 915 transmission. I've read the relevant threads top to bottom. I've drained and refilled my transmission fluid. My shifts (when I can help it) are slow and deliberate. Sometimes so slow, that I have to blip the throttle to rev match when UP SHIFTING (I have never had to do this on any other car). The car is equipped with a WEVO shifter.

I'm starting this thread because I want to separate driver error from potential transmission problems. I have driven a grand total of two 915-equipped cars, so my sample size is very low and I do not know what is considered "normal." What I may think is a sign of bad-bushings, poor coupler alignment, and/or bad syncros, may very well be evidence of my inexperience.

Take a peek at the below and let me know if you guys can confirm whether these are normal observations and/or have tips!

1. THE 1-to-2 FAKE OUT

My transmission does not simply "shift into gear." To get into 1st, one must put the shifter to the left and put the selector down about a half an inch towards 2nd, and then gently "present" the shifter to 1st. (I quickly learned that the driver doesn't decide when the car changes gear, but merely suggests it to the gearbox). While I can avoid doing the "fake out" sometimes without bad things happening, I have noticed that the "fake out" will lessen the friction/grinding into first.

This may sound like a hassle, but its really not a big deal once I got used to it. Small quirk, but at least it's consistent. Is this normal for others?

2. SO MANY NOTCHES

Going from 1st to 2nd is an exercise in patience. Sometimes, it just locks right in. (UGH, THOSE TIMES ARE SO GREAT, WHY ISN"T THIS CONSISTENT?). Other times, it feels like the shifter must be gently wrestled through 3 different stop points before landing in gear. If you rush the shifter through these notches, it will grind. If you go too slow (which is sometimes required), you lose the accelerating momentum and your RPMs are too low, requiring a blip for upshifting.

3. SECOND TO THIRD / THIRD TO SECOND

No real complaints. If I go too fast into third, I'll get some grinding (sometimes I get carried away on a spirited drive) This shift does not require the lengthy pause that 1st to 2nd requires.

4. THIRD TO FOURTH / FOURTH TO THIRD

Satisfying and usually illegal at redline.

5. FOURTH TO FIFTH / FIFTH TO FOURTH

Satisfying and very illegal at redline.

6. BACK THAT THING UP

I do not have the problem of nicking reverse (thank god). At the worst, sometimes reverse is hard to find and/or grinds.


All told, while I may dramatize what's going on with my car, the car is plenty driveable/enjoyable; and I've come a LONG way from my first 50 miles of CRUNCH EXPLETIVE CRUNCH.

What do you guys think? Am I just a novice driver who needs more wheel time and finesse? (probably) Is what I'm describing typical for a 915 or emblematic worn components?

I'm writing this post today because I may try to adjust my shift coupler on my own this weekend. I've read the how-to and seen some videos, but wanted some feedback before I potentially mess up a fine-enough shifting transmission.

[Eli W]

It needs a rebuild for sure. I was in the same boat for two years. The dog teeth from first to second are shot guaranteed. And I you think the bushings are bad as well. That is why you are hunting for first.

The funny thing is it is a mechanical but even when it is broken you can make it work. First was never a problem with me but second would grind if I was trying to push the car, but I could feel the car and drive it quite fast, and feel when the the gears wear going together and then shift.

Drop the engine and pull of the transmission and the dog teeth are going to be rounded and one may be gone from first to second. First to second get messed up the most because they get the most force when shifting

[Eagledriver]

A couple of things come to mind. Your clutch may need to be adjusted or you might not be pushing the pedal all the way down. There is no syncro on reverse so if you push the clutch in and wait about 3 seconds for the input shaft to wind down it should go into reverse without grinding. If it grinds, you need to adjust your clutch to get it to fully release. Assuming your clutch is ok, the shifting from first to second should not grind as long as you don't rush it. If that shift grinds consistently, your synco for second gear is failing.

The Wevo shifter works well for racing , but can be difficult for street driving. It's spring loaded to the 3-4 plane so you have to fight the spring to align the shifter for second gear. It also can be noisier when in gears other than 3 or 4 .

Hope this helps you.

-Andy

[stevej37]

Until you do get it rebuilt....try double-clutching between the gears. (maybe you have tried)

[Peter Zimmermann]

The 915 is all about the driver doing what the trans likes, it can't, and won't change for the driver. This can be really difficult, and if you can't achieve that it's possible that you might have linkage, or internal, problems. How many miles on the car? Is there history (I know, the odo doesn't work) of trans work? You said you changed the trans oil, what did you put in? More info, please.

[mgar88]

I appreciate all the responses already, folks. Thanks!

Pete, the car has an estimated 155K. PO installed an LSD in 2008 or so. Car was tracked frequently by PO. No known history of transmission work beyond that (though possible, there's a gap in maintenance records for the 90's). I know you're a Kendall man, but I believe the shop I went to early on only had Swepco on hand.

[Eli W]

Can you down shift into 2nd?

With no grinding. Second dog teeth are gone. I would put money on it. It should not feel like that. You are having problems because syncro and second gear dog teeth are jacked.

I just had mine done it is night and day. Grinding has nothing to do with the clutch plate although that may be bad as well, the clutch would just cause slipping when it is engaged. Grinding will always come from the the gears engaging. The feel you are getting of the steps into second are because teeth are missing and you are putting two broken puzzle pieces together.

Does not matter even if it is the clutch, drop the engine open the transmission and look at the clutch plate. In my case my clutch plate was great like brand new, syncro and second gear dog teeth were rounded over and not locking up with first.

[mgar88]

Downshifting into 2nd is fine, actually.

A rebuild is not in the cards for me, at least for a number of months. Need to save my pennies and learn how to with the syncos I have for now.

[Eli W]

Well, no worries I drove mine for two years pretty much with the same symptoms. Just be gentle with it and it will work. I could drive mine fine but just not at full tilt.

That being said the 915 is still a transmission that you have to work with, you can not push it.

If it was tracked it was pushed but that is no big deal it can be fixed. But a good place to begin is to look at the gear shift bushings and linkages and the coupler that is a very dyi job and a good place to start.

I took mine to my car to my mechanic and had him drive the car, the guy was trained in Germany in the 70s and is former race car driver, he drove the car and knew instantly that it needed a rebuild.

[Matt Monson]

On point 1, your first gear needs to be rebuilt.

Point two I would consistently try to upshift between 4-4,500 rpm. Too many shift too early. If you have to blip the upshift you aren't revving high enough in 2nd.

[pmax]

Sounds like the 915 has lived a hard 155k life. I would rebuild it now before it gets more expensive when your synchro rings disintegrate and makes confetti inside the gearbox.

[gazzerr]

You have to shift slow. Slower than you think. It's not a modern trans where you can just slam it into gear whenever you like. On mine if I "pause" between the shift and kind of "present" the shift to the syncros when shifting into the next gear (you can feel it) it's just fine. You need to know exactly where the gates are. If you double clutch it on the downshift it's much happier but you have to give it just the right amount of revs. Too much or too little and it won't want to shift. Don't force it. That's why most 915's have been abused. It takes a long time to get to learn how to shift properly. Just when I think I've got my mind around the gearbox it lets me know I screwed up the shift. . All your shift bushings need to be good and your clutch also has to be adjusted properly. That's really important.

[911pcars]

A 915 in good condition should shift like any M/T. That said, most 915 gearboxes have worn synchro assemblies with 1st and 2nd suffering the most due to the number of downshifts in those gears. 901 and 915 synchros are a unique design; not as durable as most other gearboxes. If you're the 2nd, 3rd or 4th owner, you can thank (or blame) the PO/POs for not shifting this gearbox correctly.

To extend the operating life of Porsche synchros, learn how to double clutch (see archived threads and my many rants about this). This technique minimizes synchro operation and wear while also incorporating rev matching to reduce clutch wear. Same technique. with gearboxes in good condition to minimize wear and increase your driving skill. Same with worn synchros to downshift w/o extraneous slight-of-hand lever motions.

[Drisump]

Like Matt said, higher revs when upshifting helps. I usually pause a half second in neutral before dropping her into the next gear, rev match on downshifts and make sure I push the clutch pedal to the floor. If I do all those things correctly, the car shifts very well, not fast, but well. I have driven quite a few 915s but never a freshly rebuilt one and all have had "character". Some on the board insist that a freshly rebuilt 915, new clutch, new cable, rebuilt pedal box, rebushed shift linkage....shifts great. I can't say since I haven't driven such a car. I just got the pedal box and linkage bushings from PP but haven't had time to install them. If a rebuild isn't in cards any time soon you may consider some of the cheaper but helpful improvements...the car probably needs them anyway. Cheers

[porschenut]

First thing you should do is check/replace your cup shifter bushing in the tunnel. Then make sure your shifter is properly adjusted at the rear coupler. There are chapters in the 100 Projects book on both of them. Without those two things done, it is impossible to assess the condition of synchros and dog teeth just by driving. Previous posters are jumping to conclusions.

[Lake Guy]

I've had similar concerns as the OP. I've also got limited experience and miles. This winter I've changed the clutch cable, rebuilt the pedal box, changed the bushings and adjusted everything. There were lots of worn parts so I'm hopeful this will make a big difference. I've also got a couple jugs of Swepco that I haven't put in yet. I can't wait to get it on the road and run up the miles to see where I'm at. There are some good comments here so thanks for contributing guys.

[yelcab1]

That thing needs to come apart, and you need to double clutch.

I have had two 915 and each needed to be rebuilt. One of them I had to do it twice. And then after that, it was very ... livable.

[groovydude]

You must check your bushings first. Adjusting the coupler may help. I had similar first gear issues (I'm using a factory short shift kit though). Using the prescribed technique of pulling the lever to the left and rotating the shaft to the right *might* get you where your tranny wants to be, but I found it was only in the ball park at that spot. As I said, I'm using a factory short shift, and for first and second gears mine is much happier adjusted with the shaft rotated back towards center a tad. I still have to look gently for first but it's much improved. I've read of others who had to push the lever back to center a tad so I think it varies from car to car. In my case, finding the sweet spot for first and sevond messed with 5th & reverse, si I actually modified my shifter with a rubber shim so the lever can't move as far to the left when I'm looking for first and second, and then adjusted the coupler using the prescribed technique so 5th & reverse are happy. PM me if this isn't making any sense.

It does sound like your second gear has issues, but adjusting is free so I would play around with it. I don't know if the Wevo has the same issues as the short shift kit though.

Of course, you might really be due for a rebuild, but I'd spend time adjusting the crap out of the coupler first. I also agree that slow shifts are required for the best experience - my synchros are pretty new but it still feels like I need to shift carefully. For whatever it's worth, I've driven a G50 as well and honestly I could only feel a slight difference in the shifting.

[Tremelune]

Every couple months I get similarly frustrated and go down rabbit holes of research with regard to Subaru and G50 swaps. My transmission isn't quite as bad as yours, but 2-3s shifts get tiresome, and as delightful as a good double-clutched downshift feels, it can get old.

Before I do some crazy swap, I'll probably do a top-quality rebuild with every goodie on the market today so I can truly define normal, but I have a few other things on the list before I pull the engine and lose $10k to While I'm In There. In the meantime, I'm about to take apart my shifter to combat a rattly wevo, so in the spirit of this non-rebuild thread...What is every improvement that can be made to a Porsche 915 transmission while it is still in the car?

[Nick Triesch]

This post cracks me up! What you are describing is most of 915 gearboxes on this board! When I bought my car 7 years ago I thought Holy Smokes! I need to rebuild this box! Then something happened, I learned to shift it so well I am just going to let it be. Over the years I have installed a new shift coupler behind the back seats, did clutch adjustment and changed to Kendall oil. It shifts very well . Is it perfect? No but I learned to pause between shifts, match revs and double clutch. Amazing what Kendall did for my box.