915 Shifting issue

[Ken Mikos]

1985 911 with a 915 tranny, 51,000 miles.

Replaced engine and transmission mounts, all linkage bushings with fresh grease and Swepco gear lube, added a Stomski Coupler and adjustment shifter per Pelican and manual. With all this done, I am still having problems shifting the car into first gear. In addition, 1st to 2nd can also sometimes be stiff. All other 3,4 5 and reverses are not an issue.

What am I doing wrong?

[fanaudical]

Can you better define "problems"? Grinding? Won't enter gear without excessive force? Can you double clutch from 3rd to 2nd without issue?

[grb008]

I would check the clutch cable adjustment as per manual, but if other gears are ok sounds like a similar issue I had and it was the synchro and something else on #2 many moons ago.

[Ken Mikos]

Fanaudical,
First gear sometimes grinds unless I am at a complete stop. In addition, I cannot get the shifter to engage smoothly into the first gear slot.
I can down shift from 3rd to 2nd without issue.
Sometimes I must pull hard on a 1st to 2nd shift.
Grb008,
I adjusted the clutch without improvement.
All other gears are fine other than a hard pull to 2nd gear.

[john walker's workshop]

Probably internal.

[Schulisco]

Some reports in the web claiming that only 1 out of 20 915 gearboxes work allowing to engage into 1st gear while rolling or downshifting from 2nd to 1st gear without engaging the 2nd before... In other words - those 915 are very rare. The reasons for that are still unclear. I suppose it's a combo between inproper shift linkage adjustment, gear oil with too low drag torque and wear of the synchros. But there are also reports that these problems persists after an overhaul ...so if your 915 work in all other situations, I would keep it as it is. Otherwise you're probably wasting time and a lot of money without any effect.

Thomas

[David Inc.]

Sounds like you're driving a 915 transmission. The synchros on one and two take a beating.

[shoooo32]

I had a similar situation last year on a 51k mile 1983 SC. After replacing the usual suspects (bushings, coupler, mounts, swepco, etc) it still had trouble engaging first gear and 2nd was a little crunchy if you rushed it.

So we tore the box down and found 1st and 2nd dog teeth with wear and the synchros were worn as well. The pinion bearing race had spun and a few other bearings were pitted. The case went to CMS for machining and upon return was rebuilt with a one piece bearing retainer. Now you can shift into 1st gear at 25mph without issue (heal toe downshift). Both of the 915s I've built (my 1978 SC was prior to this one) can be shifted into 1st at speed without issue.

I followed the Pete Zimmerman wiki and read most of the Pelican threads related to this subject. With fresh 1st and 2nd gear synchros, gear teeth and a new shift slider, I don't see how a 915 wouldn't shift into 1st on a roll.

[David Inc.]

Originally Posted by shoooo32

...

I followed the Pete Zimmerman wiki and read most of the Pelican threads related to this subject. With fresh 1st and 2nd gear synchros, gear teeth and a new shift slider, I don't see how a 915 wouldn't shift into 1st on a roll.

It should, mine does as well after rebuilding, but I think a lot of people expect to just pop it into first gear at a roll with zero rev matching like it's a modern Honda manual transmission.

[buster73]

Guess I am lucky with my magnesium 915/02 which still shifts fine after 300 k miles. I try to avoid to shift into first while rolling, but it is possible and can be eased with a little blimp on the throttle. Sure helps to learn shifting crash-boxes in old Army trucks. I would invest some more time in fine tuning the shift coupler adjustment.

[berndtj]

I had similar issues. Transmission was rebuilt, and shifts fantastic now. You likely also need a rebuild. I don't buy all the reports regarding the nature of the 915. Imagine buying the car new in 1985. It certainly wouldn't be acceptable to grind into 1st every time and have difficulty getting it into 2nd. When new/rebuilt, they shift great (my single data point).

[RSTarga]

I put 135k on my 915 before a precautionary rebuild, If you are wearing out the syncros you need to practice shifting technique.

[Avanti]

The 915 has always been a trans to some extent has to be learned to shift, however, may of our cars have have had their transmissions "rebuilt". The OP's low mileage SC maybe had aggressive shifting by previous owners (hey its a Porsche) causing shifting issues with low miles. Transmissions that have been rebuilt vary to the degree of parts replaced because its up to the rebuilder/tech hence subjective decisions on what to replace. This is my theory as to why the 915 owners all experience some similar issues, but also different in some way. The internals of one rebuilt 915 transmission compared to the next, are in varying degrees of wear because various parts have been deemed as "serviceable" or "good" and reused. Then they wear a little more after the rebuild and shifting challenges start. So much has been discussed of shifter rod adjustment and bushings and not enough.

My 77 S was a garage find that sat for 20 years and had 20k miles on its "rebuilt" transmission. During the "revive" to get it running, I replaced the tunnel fuel lines as well as all the shifter bushings and motor mounts. I added a new stock shift rod coupler and this is where I'm at now:

1st to second is very good almost smooth at any rpm (I don't go over 5k). I can downshift into 1st from 2nd or another gear from a slow roll MOST of the time. Sometimes, when at a stoplight, from neutral, it can be hard to get into 1st but it always goes in after a few jabs/cycles from 2nd to 1st. I adjusted the shift rod coupler with all the methods on this forum, Wayne's, John Walkers, etc. and any adjustment in any direction from where I am now, just made it worse in the respect that gears were out of range - No 1st in one direction or no 5th in another, or grinding in some way. I always ended up in the same spot I'm at now which I'm happy with and have learned to shift/live with like I mentioned in my first sentence. BTW, as another attempt to improve things, I installed a WEVO shift rod coupler with no better results. Did the whole trial and error coupler adjustments and ended up with the same results. All said, Its not a Honda with a "butter" gearbox and I'm thankful for that!

[pmax]

Quaint as it is, the 915 shifted beautifully everytime I drove it and when it doesn't, that's invariably due to user error. Most of the time, not always but most, the quest for the perfect shift is the source of fun less so the destination, not referring to the place but the gear. Of course, jack rabbit starts are prohibited, that's rule number one. I'll let someone else chime in on rule #2.

Time to get more practice.

[RSTarga]

rev matching double clutch downshifts