My First Time Into A 915 Transmission Thread

[Baby]

Hi, all. Thought I'd start this thread, as I know I'll have lots of questions throughout the process. In fact, I have one already. But first, I'll tell you how I got here. A number of weeks ago, something popped when my buddy was driving the car to the house I was moving to while I drove the moving van. The rear wheels were locked except when the clutch pedal was pushed in. I did all the tricks to try to get it unstuck and ended up pulling the panel to have a look. where to buy 915 synchros, gears etc... ?? used??

Seemed like a collar or something was broken. Since then, I have found a little time to work on the car. But I did manage to get the nose off and am in the process of removing the nuts on the reverse and 5th gears. However, I can't seem to get the thing out of neutral. At least judging by the ends of the selector shafts. Both are extended out of the case. I am trying to get the lower one flush with the case to put the transmission into 2nd gear. Tapping it with a plastic hammer, but it won't move, and I don't want to hit it too hard.

I can turn 5th gear and rotate it almost all the way around before it locks. I can't seem to move the selector when I reach up through the opening where the panel I removed was. Below is a pic of the broken collar. Looks like it's riding up on the gear. Could it be hanging up the gear selector? Any idea how I get it unstuck?

[RWebb]

you are looking at the tip of an iceberg...

[yelcab1]

That is a Synchro ring that has cleanly broken off. There are bits and pieces of it floating around inside the box. That gear box has to be totally torn down, cleaned up and inspected for all the wear. Then, parts replaced and built back up. Many thousands of dollars later ....

You need some special tools, Starting with air impact gun.

[Trackrash]

I'm guessing you have some good mechanical skills. A simple mistake on these transmissions will have you starting over again from scratch.

First thing to do is read this How-To: Porsche 915 Transmission Repair Tutorial Part 1 - Porsche Wiki

Then do a search, several 915 rebuilds have been documented on this board.

You should also get a copy of the workshop manual.

Good luck.

[Baby]

Thanks for the encouragement. What I'm looking for is some insight specifically on clearing that broken piece out of the way (without causing more damage to the gears) so I can engage 2nd. I would like to engage 5th, too. Then I can spin off the nuts and remove the cover.

In the original post I should have said "shift fork"instead of "gear selector." I think the broken piece may be stuck on the gear and preventing the fork from moving as far as it needs to. If I can't clear it and get into 2nd gear, I'm going to have to find an old clutch disk and make a tool to lock the main shaft. Wondering if sliding it back into place could be OK or if I should leave it in place, lock up the shaft another way, and pull/cut it off when I have clear access to the gears.

As far as I can tell, this specific circumstance isn't covered in Peter's tutorial or Bentley, and I haven't run across it in any thread on this or other board. I appreciate any advice.

[kodioneill]

Originally Posted by Baby

Thanks for the encouragement. What I'm looking for is some insight specifically on clearing that broken piece out of the way (without causing more damage to the gears) so I can engage 2nd. I would like to engage 5th, too. Then I can spin off the nuts and remove the cover.

In the original post I should have said "shift fork"instead of "gear selector." I think the broken piece may be stuck on the gear and preventing the fork from moving as far as it needs to. If I can't clear it and get into 2nd gear, I'm going to have to find an old clutch disk and make a tool to lock the main shaft. Wondering if sliding it back into place could be OK or if I should leave it in place, lock up the shaft another way, and pull/cut it off when I have clear access to the gears.

As far as I can tell, this specific circumstance isn't covered in Peter's tutorial or Bentley, and I haven't run across it in any thread on this or other board. I appreciate any advice.

I don't think you understand what the guy's are saying, that transmission may well be junk at this point if you pull that syncro ring out"if you can" and drive the car it will be junk for sure. It needs to be pulled taken apart inspected for damage to the other components and you just might get lucky and have some minor damage.

[Trackrash]

I'm assuming you have the transmission out and the nose cone off.

I would jam the gears with a rag and use an impact to remove the nut.

Or loosen the shift fork nuts to be able to engage two gears at once.

[yelcab1]

Originally Posted by Trackrash

I'm assuming you have the transmission out and the nose cone off.

I would jam the gears with a rag and use an impact to remove the nut.

Or loosen the shift fork nuts to be able to engage two gears at once.

I have done that but did not want to post it because it is so ... hacky. It does work very well.

[jm993rs]

Very good

[john walker's workshop]

when the 1st syncro gets loose like that, it can squish the bore for the 5th gear shift rod, so it can't get into 5th. be sure to look at that so you don't have to tear it down again. also, research detent position. and use kendall 80/90 gear oil, not that blue stuff.

[Peter Zimmermann]

^^^What John said...

This is one of the few times that I'm OK with using an impact wrench.

[Baby]

Originally Posted by yelcab1

I have done that but did not want to post it because it is so ... hacky. It does work very well.

Ha! No one wants to be that guy who suggests jamming gears with rags or hitting things with hammers, but in this case it's exactly the kind of info I'm in need of. Thanks. Hopefully I can get to this tomorrow.

BTW, JW, I ran Kendall in this car until a few months ago, when I thought I'd try out the other stuff. I'll go back to it if I can find it when the time comes.

[ischmitz]

From your blog it looks like you rebuilt your 3.0SC engine. So you are mechanically inclined. The 915 needs a complete tear-down. Impact wrench and rags are the way to go to get the large nuts off. For assembly you later need to make a holder for the main shaft. I used an old clutch disk to make a wrench - works fine if you don't want to pony up the $$$ for the original tools.

One more piece of advice - try to not remove the shift forks from the rods. Adjustment of these requires jigs or lots of experience during re-assembly. After you remove the bearing retainers the rods come out of the housing with the forks in theirs sleeves. You need to make sure to remove the detents.

I rebuilt my 915 and the Porsche workshop manual was an excellent source of information together with the tip above.

Good luck,
Ingo

[Baby]

Originally Posted by Trackrash

I'm assuming you have the transmission out and the nose cone off.

I would jam the gears with a rag and use an impact to remove the nut.

Or loosen the shift fork nuts to be able to engage two gears at once.

The rag worked like a charm. And thanks for the other tips---adding them to my notes.

I hope to get to the gears this week and post some pics of the internals with the hopes that some of you guys who have seen a gear or two before can share your thoughts on the condition. If need be, I can take the stuff to one of the 911 shops around here for some advice.

Off topic, I mentioned that I recently moved. Lots of things to be done---painting, bathroom fixtures, etc.. so I'm not able to work on the car as much as I'd like. I'm working in triage mode, having carved out some space in the shop and scattered a few tools around. On the plus side, lots more space here than in the last place. Looking forward to getting it set up...

[beren]

Nice blog! Bookmarked that for the future.

[Baby]

Thanks, beren. I need to find some time to update that thing...

Here are some preliminary shots of a few gears with the housing removed. Some battered dogteeth are easily visible. And that gear in the last pic has seen better days. Time to disassemble, clean and inspect.

One question: is it likely that bits of the snychro are in the diff? Will I need to strip that down and clean it out?

[Peter Zimmermann]

It's best to post pictures of parts that have been washed & dried; makes it much easier to assess condition!

[john walker's workshop]

yes, open the diff and clean out the debris. to lift the gear stacks, shift rods and forks out of the diff housing as a unit, engage 3rd gear, remove the 2 side detents, grab the whole works, lift and wiggle it out.

[Peter Zimmermann]

For the side detents, use a small magnet to draw out the springs & detents. Remove the 10 nuts & lock washers holding the upper & lower clamping plates, grab & pull. I remove the shift fork bolt from 1/2 fork, and leave the 3/4 fork on its shaft. Don't worry about "losing" the fork adjustment, I spend a lot of time in my Tutorial on those adjustments, and it will make sense as you re-assemble. Never assume an adjustment is/was correct, adjustments are only as good as the last guy that was in there.

[Baby]

Will do, and thanks, gents. Rest assured I'll post lots of pics once I've cleaned everything thoroughly.