915 2nd gear shift question, temperature dependant

[jjeffries]

My 82 SC shifts beautifully ito second, up or down, when cold. When the car is thoroughly warmed-up, however, second becomes a bear to get into, up or down, on approx 50% of attempts. It's either good, or very difficult. There is no grinding. When this happens, one needs to patiently and gently make a couple of more attempts, then it will eventually let the shift happen.

The car is new to me, and my first 911. I've read much of what is out there on the 915, and other than this issue, I like the gearbox's action.

Salient facts:
- 183k miles, one owner till 2013, next owner till 2014, then me.
- 1st & 2nd synchros replaced 10k miles ago for OO by shop in Maine; no other parts charged out on invoice....no sliders, etc.
- gearbox and final drive don't make any funny noises;
- coupler and shifter bushings replaced by PO; I pulled console and checked they are all in place, in as-new condition and well greased; ditto the coupler.
- I believe I have the linkage properly adjusted as per Peter Z's guidelines.
- recent Sachs clutch, properly adjusted.
- no limited slip diff.
- just changed the oil with Kendall; believe what came out was Kendall also; no metal chunks in it, just pearlescent coloration in oil; didn't make any difference.
- I'm gentle on the gearbox; been an Alfa guy for years, so know about touchy 2nd gears; I'm not a speed shifter.

As said, this is temp. related.....perfect when cold. What inside the 915 would cause it to act this way?

I bought the car with the motor in boxes and successfully rebuilt that (with much help from folks here), but I'm less enthused about tearing into the 915; I will likely take it out but then have one of our excellent New England gurus help me, and I realize that the answer may be "disassemble and look for worn components". But, ideally, I'd like to first understand the root cause.

Thanks in advance for any help that can be offered,
John in CT

[Reiver]

An almost out of spec internal part(s) that when warm expands and is out of working spec. No way to figure out without opening it up.

[jlynch1960]

Mine's the exact opposite. Shifts fine when warm, but a little hesitant when the temperature drops.

[Rich Gas]

Mine is slow to go into 2nd...first and second synchros at 86k...120k now.... Wish I could help, interesting problem.

[82 SC]

Weird, my 82 is hard to shift when cold but the warmer it gets the easier it is. Good luck and let us know what you find.

[Lake Guy]

some similar things for me - 185K miles on an '84, don't know about previous repairs/upgrades. Shifts reasonably well up to second if i'm patient but not what I expect and want better consistent action too. I've bought a bushing kit and Swepco 201 but not tried either yet. I hope that does the trick for me but i'll follow this to see if any other ideas pop up.

[uwanna]

Just a guess, but here goes. You mentioned OO had new syncro rings installed, which is a VERY precise part. Even with new rings there is a precise installed measurement, and lately there has been some problems with some after mkt mfgrs new syncro rings. (particularly Rauch & Spiegel)
My thinking is if the installed diameter of your 2nd gear syncro is too small, the friction to cause correct "syncro action" is insufficient . Ergo, when your oil is cold and thick the friction would be better, but when the oil gets hot and thin, the friction of the ring may be marginal. Just thinking out loud, LOL

[Matt Monson]

R&S is not an oem supplier.

A lot of people shift too early into 2nd. 4000 rpms is kind of the sweet spot.

[jjeffries]

Thanks gents. UWANNA, your analysis sounds logical to me. Best, John

[jjeffries]

Matt, that's something I didn't note in my original post; I'd read your RPM advice elsewhere, but that doesn't affect this situation. When 2nd gear gets cranky, it doesn't discriminate as to whether lower or higher revs are used. I'm shifting with empathy, using finger pressure only. I had Tom Butler drive it and he experienced the same. It's a good:bad, yes:no, will accept the shift/not accept the shift kinda thing, one or the other. thanks, John

[Matt Monson]

Might be the selector finger on the base of the gearbox that directs the master shift rod.

[uwanna]

Originally Posted by Matt Monson

R&S is not an oem supplier.

My mistake Matt, meant "after market". Have read your comments on dissatisfaction with some Rauch & Spiegel stuff.

[kyngfish]

Not sure how long you've had it, but I recently bought an 86 Carrera, and to be very honest, the first three weeks I was afraid I had bought the wrong car. The shifting was vague and miserable, getting from 1-2 was a pain.

Nearly 3k miles later, the shifts feel easy peasy. For 1-2, I either shift at around 3k RPM or I shift at almost redline. Anything in between and it doesn't feel like the motor has enough momentum for hard acceleration, so the shift feels slow and weird.

The experts here are probably right, but my level of comfort with the 915 is hugely different now than it was when I got the car. My suggestion is to give it some time, and drive a lot.

[Peter Zimmermann]

John; your statement regarding replaced synchro rings, but no sliders, might be the biggest clue to your shifting issues. Often, if synchro rings are replaced, but the old slider(s) are used again, a very long break-in mileage period can occur, because the old slider will have wear that can prevent smooth gear engagement, that might "fix" itself or may never be satisfactory. You're at about 10K miles now, so you're getting pretty close to the point when you're going to live with the inconsistency, or open it up, measure the synchro rings, and replace the slider.

FWIW; your problem is exactly opposite of the norm for your model car. In my opinion you're using the best oil, as long as it's Kendall 80w/90 DINO, not 75w/90 SYNTHETIC, to help with shifting difficulties. That said, using new synchro rings combined with used sliders is almost always a recipe for trouble. Continue to use the "two-part" shift, and shift at that 4K rev "sweet spot" suggested by Matt. Keep us posted regarding progress!

[Arne2]

I've got about 23k on the synchros and sliders in my 915, and with the correct Kendall in it, it shifts quite well. (Much better after I went from the factory short-shift back to stock shifter throw.) A bit stiff when cold, but very nice in all ears when warmed just a tad.

My papers do show the sliders being done with the last set of synchros, so Peter is probably right on the mark with this.

[jjeffries]

Thanks gents, especially the specialist feedback from Messrs Monson and Zimmerman. Yes, the Kendall is dino; I bought a case of it locally. I'm quite prepared for the gearbox needing to be opened-up; the extent to which this 2nd gear baulk-when-hot marrs the overall driving experience is considerable, and is not something that merely requires a more patient method of shifting.

Maybe the new synchro ring and the old slider will "make friends"....one can hope.

Thanks again, John

[javadog]

I once had a 930 that had a bad 3rd gear synchro replaced, without a full rebuild. Most shifts were fine but one in every 8 or 10 had balking problems. It wouldn't complete the shift and there were gentle, rubbery vibrations fed back through the lever. Putting it back in neutral and making the shift again usually worked. It got a little better over time but never went away.

My suggestion is to open the box up and repair it again, properly. Peter Z's tutorials are great for educating you as to why certain things need to be done, even if you are not the one doing the work.

Good luck,
JR

[jjeffries]

Thanks JR. That's a good description of what I feel when it won't go into gear...."rubbery", nothing grinding or sharp feeling. But it can take 2 or 3 careful shifts between Neutral and 2nd to consumate the gear selection.

I've read the Peter Z tutorials. I feel like the gearbox is the most watch-like and complex unit in the car, and while I could likely follow the necessary steps, as a noob I'd still be lack the eye for the qualitative decisions that need to be made, and for the all important "how much force to apply?" situations I'd encounter. For that reason alone I will engage (haha...gearbox pun!) the help of someone who knows what they're doing.

cheers,
John

[javadog]

I was not suggesting you do the work, only learn what likely needs to be done, so that another repair to the same problem isn't 'incomplete." I'd bet half of the transmission work done on these old gearboxes cuts a fair number of corners, as to do it right can get expensive.

That's why you want a really good guy to go through it.

JR

[jjeffries]

Quick update, approx 4k miles more on this car (82 SC coupe, 187k miles) since I got it, rebuilt the engine and first started this post:

First off, I subsequently realised that I may have bent the shift shaft when I installed the motor/915 assembly. I did this job on my mid-rise lift, also using a HF 1000lb hydraulic lift table. The first lift table leaked pressure, and that was how I came to oval the (stout) hole on the rear bulkhead; got that table replaced by HF. I read lespaul's (Brad) description of fixing this shaft without a full 915 teardown...really clever bit of Vermont engineering. Question: would a bent shift shaft cause my sometimes good/sometimes bad 2nd gear up- and down-shift problems?

I'm now not so sure how temperature defendant this problem is. Can happen anytime.

The nose casting that contains the shift shaft seal seams to be OK. It was leaking (and clearly had been been leaking since before I got the car), so I removed and replaced the seal in situ. It continued to leak, so before repeating myself I just nudged it in a hair deeper (erotic 915 stories) and the leak stopped.

I've checked the fork on the inspection plate at the bottom of the gearbox and it was tightly fastened. I've also changed the oil a couple of times, always Kendall 80/90 dino (bought a case...)

I've removed the inner shift shaft boot, in case it was bunching/binding.

With 4K more miles on it, sometimes I think it feels better, but then figure my head is playing tricks with me. I will pull the engine/transaxle this winter and sent it to someone good for inspection and repair. I know PeterZ said when I first posted that new synchros with old sliders was a bad idea. I'm upshifting at 4-4.5K rpm. It goes into first most happily when the car is rolling. Maybe I shouldn't conflate my first gear stories with those of my second gear's.

I will update when the next steps occur.
John in CT