915 Trans 1st to 2nd shift at red-line

[8nthatK]

Hello all.
I’ve been doing a lot of reading deciding exactly what my first Porsche will be. A 911 certainly and I have narrowed it down to either the ’84-’86 years or possibly spending a little more for a year or two later G50 trans model. I would like to save a few bucks and go with the 915 car. The shifting ‘issues’ of the 915 tranny doesn’t bother me in the least, well except for one possible ‘issue’. I have read about the apparent trouble of the 1st to 2nd gear shift at redline and find myself a bit confused. It seems many have to either shift early or let the engine wind down before making this shift...I don’t see myself doing a 1st to 2nd shift at redline often, but I wouldn’t be happy if it couldn’t be done.
Is this a wear issue (synchro’s) or something inherent in this transmission type? That would surprise me…
So, for those of you piloting a 915 car with the trans in good shape, is this a problem? I realize it is a slower shifting trans, but it doesn’t seem reasonable Porsche would put out a vehicle where a 1st to 2nd shift with the engine wound up would be near impossible.

Thank you much for your time and this wonderful resource here.
-K

[dan79brooklyn]

It can be done...Just need to develop a feel for the transmission the particular 915. After more than two years of owning my '79 with a short-shifter I still get a difficult shift from time to time.
Test drive both a G-50 and 915 to see if you have a clear preference...

[911pcars]

Upshifting is not as much of an issue compared to downshifting. First to second gear shifts at whatever engine speed is the same relative difference in speed between the unmeshing and meshing parts.

As long as the upshift from gear to gear doesn't stress the synchromesh assembly, the drop in engine speed between 6000 rpm in 1st and 4000 rpm in second (depends on gear ratios) shouldn't create any more wear than a first gear shift at 4000 rpm.

Sherwood

[Zeke]

Hey, ain't that, welcome. Yeah, just needs a little time and finesse between all the gears. The bigger the RPM drop, the longer the synchros take, as Sherwood indicates. If you've got a really quick left foot, you can double clutch it and pick up a fraction of a second as well as help out your synchros. Once you get rolling off a dead stop, you won't use first much anyway. No one ever does at the track.

[Mattcamp]

I have no problem shifting from 1st to 2nd at redline with my 915. Maybe this isn't the case with a higher milage car.

[DanielDudley]

If you have the knack, you can do that shift into second with practically shot syncros. There is no problem with the shifts, you just have to do it the way the tranny wants you to, not the way you feel like doing it. Some of my PCA friends feel that they can shift a 915 box faster than a G50. Not sure I agree, and if I had a G50, I'd probably get spoiled quick. I have good syncros though, and love my car. I persnally have more trouble getting into second at super slow speeds, and sometimes have to blip to get in on the second try. No point in forcing it.

[8nthatK]

Thank you folks.
Thanks for the welcome Milt!

I understand it shouldn't be a wear factor (excluding man handling) just seems like a lot of people are concerned/disappointed with this shift?? I don't think I'm going to concern myself with it... double clutch etc. isn't an issue on my part, so I'm sure I can adjust.
I just wanted to be sure this wasn't some strange anomaly with this trans.
…funny thing is I turned wrenches for Porsche (dealer) in the early ‘90’s and don’t remember any issues, but started to wonder with the comments if I had ever did a strong pull from a stop in a 915 car. Seems like I must have at some point ; - )

[KTL]

Wear is a big factor in getting a smooth shift in your 915. Especially in the case of 1-2 because this assembly sees the higher loads due to the increased torque multiplication of the lower gears. Since these see the higher loads, they resultingly see higher wear? Plus the 1-2 upshift or the 3-2 downshift is the most common "speed" shift that occurs in most street driving.

The difficulty in shifting arises from a number of factors:

-Loss of friction surface on synchro band
-Damaged/blunted teeth on synchro hub
-Misshapen ID of synchro operating ring/sleeve
-Wear on contact surface of operating hub

Like I said, the above items are typically most worn on the 1-2 synchronizer assembly because of the aforementioned high loading and hard shifting occuring very often. 3rd gear is the next most common one.

[8nthatK]

Originally posted by KTL
Wear is a big factor in getting a smooth shift in your 915.

Hi KTL.
Thanks for the comments.
My "I understand it shouldn't be a wear factor" comment was actually in response to 911pcars' statement; "shouldn't create any more wear than a first gear shift at 4000 rpm."
Just to clarify : )
I think '922pcars' misunderstood my original post thinking I was concerned it would CAUSE wear (no doubt a sloppy shift would).... Then again I may have misunderstood his response.
Anyway, it makes since the worn parts you mention would cause a more arduous shift, I don't mind maintaining/rebuilding. As long as I can stroke thru them reasonably well in a tight and right trans! Which sounds to be what you are saying also.
Very good!


You all are a great help, thanks!

[DARISC]

My 915 has 191k miles on it - rebuilt once, 123k miles ago - really!

Have no problems upshifting in any gear at redline.

Have no problems down shifting either. Double clutching can help and I often do but not really necessary on mine.

I listen closely when rev matching and have no problem.

Mine will go into 1st at 35/40mph w/o double clutching if I want it to but don't see much point in doing so.

From what I've read re garding 915 trannies over the past 2 years that I've owned my SC, I guess I'm lucky - (personally, I don't prefer the heavier/stronger G50, but I don't track my car).