Today is the day - much needed 915 upgrades

[ischmitz]

Well, to be honest some of upgrades are needed and some wanted:

During my last transmission oil change I found several tiny hollow metal squares stuck to the magnetic drain plug. At first we couldn't make rhyme or reason of what these were or where they came from. But then realization set in: The early 915 main shafts has 8 teeth that hold the gear stack in place and the pieces looked exactly like these. It's strange they are hollow inside. We found five or six of these. I wonder where the rest are:



Apparently these came off sometimes during the 40,000 "gentle miles" of this 915 being mated to the 3.6. The later main shafts have a solid piece here for added strength. Makes sense:



This might also explain the high-pitch grinding noise when I shift into second and push the shift lever too much towards 2nd in the process. If this is true it must have happened quite some time ago. At first I though this was a dry pilot bearing. I probably did more than 10k miles with these pieces snapped off. And I did another 2k after the oil change as this is my daily driver. I am curious what we find when we open up the 915 tonight. Probably a loose gear stack? I'll snap some pictures. In the meantime I went on a little shopping spree and here is what is going to go into the 915 today and tomorrow. Not pictured are the beefier hubs and sliders for 1st/2nd and 3rd/4th.

[Matt Monson]

I hope you have the matching idler gear to go with that mainshaft. If you don't and mate it to your old 1st gear idler that sucker is gonna howl like a banshee.

[DRACO A5OG]

Oh Man!

Keep us posted! :-)

[ischmitz]

Originally Posted by Matt Monson

I hope you have the matching idler gear to go with that mainshaft. If you don't and mate it to your old 1st gear idler that sucker is gonna howl like a banshee.

Matt, I sure do. I was just too lazy to take it out of its baggy for the picture. Also have the upgraded stop and anchor block parts.

[Matt Monson]

Originally Posted by ischmitz

Matt, I sure do. I was just too lazy to take it out of its baggy for the picture. Also have the upgraded stop and anchor block parts.

Excellent. I didn't want to post a "don't kill the messenger" reply.

Looks likes a fun project. Should be a great drive when its done.

[ischmitz]

No surprises here, a little tooth decay....

[DRACO A5OG]

Whoa

[jlex]

Bit of JB Weld should fix that up

[MARISOL78sc]

My 915 is being opened up as we speak as getting into 1st is almost gone.....dogteeth are most likely gone but will be going all in for the long haul.

[ischmitz]

Well, the transmission got done but then the day ended on a low note, argh. Win some, loose some. So I have to wait one more week to tell how the 915 works with all the goodies:

http://forums.pelicanparts.com/porsche-911-technical-forum/908678-attempted-leak-fix-3-6-ends-disaster-need-comlete-teardown-argh.html#post9063782

[KTL]

Ingo,

I'm curious how was the fit of your splined 2nd gear on the "new" mainshaft. In my racecar 915 I found an insufficiently tightened mainshaft nut (whoever didn't tighten it enough still staked it on the shaft though!) and that allowed the stack to walk along the shaft ever so slightly. The shaft splines were shagged, as well as the splines in 2nd gear, the spacer sleeve next to the stop/shoulder of the shaft was smushed a bit and the idler 3rd gear's splined bearing race was broken.

Porsche did well to have that shaft shoulder revised but they should have done something better than the thin spacer sleeve that locates 2nd gear.

Sorry to see your crank dilemma on the other thread.

[Tinker]

You've had that a motor / trans combo for a while? How long did the trans last?

I sheered the teeth of off mine within the first couple of months. Thought it was just a weak shaft and replaced with another and promptly sheered the teeth off that one within a month. Doesn't take me too long to figure things out eh?

Next one was the later style with the collar and its still going strong.

Lessons learned.

Sorry to hear about your motor problems.

Tinker

[ischmitz]

Kevin,

2nd fit fine onto the new main shaft. The stack was definitely loose once the teeth came off on the original shaft but apparently not too much damage was done to the splines. Everything looked fine and we literally went with a magnifying glass over all the parts. This is how a used operating slider for 3rs/4th got disqualified and I bought a new one on the spot. I also upgraded 1st/2nd and 3rd/4th with the later wider hubs.

I am anxious to see how the Wevo stuff will do. Looks like we are getting away w/o having to tear down the 3.6 and I might be rolling home in my own ride before the weekend hits.

Ingo

[ischmitz]

Quick update on the 915 upgrades. After a lucky turn of events (didn't have to tear down the 3.6 after all) I was able to complete the upgrades today. I am in awe!! Gone is the squealing noise when pushing the lever too far into 2nd. This was definitely the loose stack on the main shaft starting to interfere. Even before the upgrade the transmission shifted fine. For good measure we flipped the synchros and installed a brand-new 3rd/4th operating sleeve. The dog teeth on everything were perfect. The synchro profiles were still symmetric with minimal wear, no bald spots.

The Wevo stuff sure makes a world of a difference in how the shifts feel. I first test-drove the car with the internal gate shift installed only. The gates weren't as restrictive as what other predicted. I've heard people comparing the feel to that of and old Ferrari with the gates on the shifter cover and that you have to develop new muscle memory. Not true IMHO, it felt pretty transparent to me.

Today we dropped in the Wevo shifter and coupler and replaced the tunnel bushing. All I can say is WOW. The shifts are now super-predictable and everything feels great. I really like the definition of 3rd/4th. No more sloppiness. Does it shift like a modern gearbox? No, I can still feel the synchros because it's a 915. And I like that. I usually allow time for them to do its job before fully pushing into the next gear. But the precision and location of 3rd/4th plane is awesome. And no I get much more feedback from the transmission during the shifting process. And last but not least it looks cool, too:



And after getting all the dog hair vacuumed out.....