Need help on a recent 915 rebuild as its a disaster

[Trackrash]

FWIW, a few years ago I rebuilt my 915.

The dog teeth I received were not back cut. I asked on this board about it and got no intelligent help.

I ended up cutting the correct angle on the dog teeth on my lathe.

I discovered the defect when I measured the installed diameter of the synchro band.

At any rate, the installed diameter of the synchro band was undersized. Which would make it shift into gear too easily, not too hard. Of course it would not last that way very long...

[Matt Monson]

Originally Posted by Trackrash

At any rate, the installed diameter of the synchro band was undersized. Which would make it shift into gear too easily, not too hard. Of course it would not last that way very long...

When the synchro is over compressed like that it doesn't generate enough friction to properly slow/speed the idler gear to allow the slider to smoothly engage. Yes, it lets it shift too "easily" which will make the engagement teeth on the gear get banged and slammed, or what most call "crunch" going into gear. It. I'll act like a synchro that is worn out.

[dicklague]

I am not sure how much this will help, but will add my 2 cents and 915 experience.

About 8 years ago I had TRE rebuild my 915 trans in my 1973 911. Gears, bearings, synchros etc.. and we put in the WEVO internal shifter gate

I had a weltmeister shifter and stock coupler in it. Shifting was horrible with the rebuilt trans. Dave at TRE said it was the shifter and sloppy linkage.....so I put in a factory short shift kit, replaced all bushings and put in a Wevo coupler. Problem solved.


The WEVO shift gate would not tolerate the sloppy mechanism.....It has been great for years now and is probably the best 914 I have driven.

I am very glad I DID NOT remove the shift gate. I feel this makes it very positive and precise shifting.

[ReconTrojan]

Well to complete this thread I got my car back today.

It shifts really, really well. 2nd gear is "sometimes" tough but I was told with the new everything its just really tight and after use it will continue to get better. I guess Im so excited over finding first gear I just don't care.

So the plan is to drive it for 2-300 miles and adjust it again.

The WEVO internal gate was removed. Funny looking at it I had to chuckle at what has to be a healthy margin considering what it actually is. ( I never got to see it before installation) But the gearbox was basically done twice and it feels really good going through the gears so at this point I am relieved and happy.

I will also give my impressions of the Porsche Classic Nav system sometime soon as I got time with it and am very happy I got that as well. Now that I have spent a tidy some, time to put the car in rotation and drive it.

Thanks everyone for your contributions, they were informative at every level.

[gomezoneill]

I rebuilt my 82 sc 915 last winter. When I tried to shift it at first it wouldn't go into any gear except reverse needless to say I was shaking I was so pissed. I kept trying to engage the gears then it went into first, ok good, then second and finally after nursing it I got all gears and after about 300 miles the trans shifts beautifully smooth as silk I think things were just very tight at first. I don't know what manufacturer made the dog teeth (I got them from our host) but I had a hell of a time pressing them on straight. I thought I broke the second gear dog teeth as it was so hard to align the splines and made a BANG when it pressed into place. Just my rant on how transmission rebuilds can be a pain.

[Trackrash]

It does take some time to really break things in in these 915s. In my case I could barely get it to go into any gear when I was testing it on the stand after reassembly. It felt like I would break the shift forks.

Now a thousand miles later it shifts into first when moving. Moving slowly, that is.

[ReconTrojan]

Thanks guys, I drove it some today and I can tell things are new. But it's going to be great I can just tell.

Whats so weird is how well my same year 951 shifts and of course my modern Porsche shifts like butter. These are just different animals.