Hi all, I have done a lot of work trying to narrow down the source of an irritating rattle with my 914. Any insight into what is happening here would be very appreciated!

On very rare occasions this rattle will present itself when the car is in neutral idling (parked - not moving). But always present when the car is moving. It is hard to hear above 20-30mpg, and mostly noticeable when coming to a stop.

It does not matter the position of the clutch, and it is not coming from any of the shift linkage (i can hold tension to the linkage or let it swing loose in neutral and the rattle is still present). The rattle is present in neutral and in all gears EXCEPT for 1st.

1st gear is the only gear where the rattle disappears. if I am coasting to a stop and 1st gear is engaged (with or without the engine running) there is no rattle. If I pop it out of 1st gear the rattle starts immediately.

Also (if relevant), I have never been able to smoothly downshift into 1st gear when the car is moving (I have done it but I have to double clutch/rev match to accomplish it). Could this also be a symptom of this issue or is this normal?

Thanks again!

Might be the throw out bearing or something related? Does the rattle end when you push in the clutch? Just guessing here, but I did have this happen in a non-914 so I presume it could happen in a 914 too.

Paging @DrEvil

@DrEvil you are wanted in surgery consulting.....

My first thought was that it was the shift rod hitting the the cooling tin aft of the firewall that's causing the rattle, but you said that while holding the shift linkage you could still hear the rattle. Did you hold the linkage from under the car? If not, try that to fully rule that out.

If you did crawl under the car, what side/end/part of the transmission is the rattle coming from?

Regarding downshifting into first when the car is moving- I think general consensus is that doing that isn't good for the transmission. That said, I doubt it has anything to do with the rattle from a mechanical point, but going into 1st does put the shift rod into a different position with respect to the engine tin I mentioned above.

I did double-check the linkage around the tin (which is definitely a tight squeeze) but everything clears in all gears. The rattle is definitely coming from inside the transmission, but hard to pinpoint exactly where while the car is running and parked (since it doesn't always rattle when the car is not moving). The best I can tell, it's somewhere near the rear of the transmission.

Just bumping this up to see if anyone else has any ideas or help with this before i pull the transmission apart. Thanks again to all who gave me ideas so far!

I it's coming from the rear, any chance the bolts for the transmission mounts are loose?

How about posting some audio of the rattling sound?

Sure, sorry I should have attempted that earlier. Here is a video. I tried my best to get the rattle while it wasn't moving. At the 21 seconds in you can hear the rattle stop (this is me pulling it into 1st gear). At 23 seconds I slide it back into neutral and the rattle starts again.

https://youtu.be/luXRCnLRZrA

This rattle is definitely coming from inside the transmission.

It sounds very much to me like it's on the outside of the transmission somewhere, not the inside. Take a piece of rubber hose, put one end up to your ear and the other move around the tranny until you can isolate where the noise is originating from.

If it is not rattling in 1st gear but you hear it in all others, it could be the positioning of the 1-R shift fork. If the fork is set so the slider is positioned slightly off, the slider will touch on the 1st or reverse gear when not engaged. If your rattle goes away in reverse also, then I would be suspicious of this adjustment. Good news is IF this is the case, the adjustment can be made by removing the tail of the transmission only.

Thanks Morrie! I just wanted to stop back in here just in case what i found helps anyone else.

Once I dug into taking the rear cover off I found that someone else had been in there before and the thrust washer and bearing are missing from the reverse idler shaft which would explain the reverse idler gear clanking against the slider like you described.

I will order replacements and put it back together and report back on the result.

Thanks again for your help.

Ben

Hi Ben,

Assuming the gears are okay, I can probably hook you up with spare parts from what I have lying around. Send me a DM and we can arrange. Since I am just up here in Austin you can get the parts fast.

Morrie

Thanks Morrie, saw your post too late and got some parts already, I appreciate it though! Also, all gears back there look to be in great condition... I will probably tear into it deeper later this year when I start a more in-depth restoration.

I found a used washer/spacer in real good condition (Porsche told me none exist new and it would be a 4-5month request from Germany, but a used one is perfectly acceptable considering what its purpose is), but they were able to get me a new thrust bearing.

got everything cleaned up and put back together (correctly this time) and it's smooth as butter... not a single rattle (imagine that ). I can now sleep at night. Here are some pics of the parts missing...

Good Job Ben! Glad it all worked out. When you dig in later let me know if you need any little bits. I tore a couple of these down and saved everything "just in case" someone needs it.