I believe that the 991.1 7-speed manual transmission is prone to failure of the internal mechanism that engages the backup lamps when the vehicle is shifted into reverse gear. There have been several reports on here and I have experienced this failure and had a Porsche trained mechanic with over 40 years experience examine the transmission. The piece that engages the backup lamps has simply fallen off inside of the transmission. I believe this mechanism that engages the backup lamps was either made with defective material, made with material of insufficient tensile strength, was not attached properly in certain models, or was designed in a manner where too much tension was placed on the mechanism while engaging reverse gear and/or the backup switch.

I attempted a goodwill repair, but Porsche refused and will not offer any parts aside from a complete transmission replacement. The cost is over $15,000 to get reverse lights working.

I intend to file a Petition with the administrator of the NHTSA and pursue other civil remedies, but first, i need to have my transmission examined in order to determine the precise cause and nature of this failure. I also need the broken mechanism replaced so I can safely drive my vehicle.

The hard part is that there do not appear to be any rebuild kits available in the U.S. - or any of the seals/gaskets necessary to put the transmission back together. I also have not found a way to get a new mechanism to engage the reverse lights.

Is anyone here aware of any parts supplier that would be able to get these parts either in the U.S. or able to ship to the U.S.? Any help or information is appreciated.






Does anyone have any information on any parts supplier that is able to obtain the parts necessary to rebuild the 991.1 MT?

 

There is a solution here. I'll find the old post for you.

 

Colvin, here you are:

https://rennlist.com/forums/991/1077...-says-15k.html

 

Thanks - but its not the solution i am looking for due to a safety concern. The piece is substantial in size and falls into the transmission. The micro switch solution makes the backup lamps work - but doesn't remove the large debris from the transmission. As such, there is a risk that the debris will cause the gears to lockup and result in an accident.

To illustrate what I'm talking about -- see the diagram below. The backup switch is identified with blue cone. The piece that has fallen off is identified with red cone.

 

Another long shot - anyone have access to the service manual for disassembly of the manual transmission?

Does any have access to part numbers?

Lastly, would a 991.2 transmission bolt up - if I went that route? I don’t want to buy used 2012-2014 transmission with same issue but I believe there was transmission part number change in 2015 and again in 2016. Maybe this was addressed.

 

Just wondering here, if part that may have broken off, is metal, would it not settle to the bottom of the trans? If so, I’d attempt work-around for reverse lamp and keep on driving. Does normal operation of trans create currents within box that would actually move a metal fragment? I’m not sure if manual trans use a pump or just rely on gears, dipped in trans sump, to move oil around. Could trans be scoped from drain plug hole?
My only experience with similar is a 1976 BMW boxer engine that ran fine. Being OCD, dropped oil pan to find timing chain clip in pan. Even with oil pump doing its job, as long as the timing chain had stayed together, I’d never have known.
Ignorance is bliss, sometimes.

 

Does the 991 trans drain plug have a magnet? Prior 911s did. If it has a magnet, and the the broken piece is ferrous, it's possible it can get caught?

 

Are you suggesting the issue was fixed for 2015/16 cars?

 

To OP. Just because it does not work, does not mean it is loose in the transmission per post #4 with the picture.
It may just be weak switch or no contact.

 

The plug does have a magnet. The fluid was drained and no debris. The old transmissions used a small pin on the rod - but the ZF transmission appears - based on the Porsche diagram - to use a different design with an independent bracket attached to rod.

I have not been able to find any photos of the actual internals.

The mechanic put a bore scope in the spot where the backup switch goes into the transmission - with car in reverse gear there is no bracket or mechanism visible at all (when it should be pressing the button on the backup switch). Unfortunately I don’t know at this point where exactly it broke or how large the piece is. I don’t even know what type of metal used.

I do believe that after it broke - It fell and briefly prevented me from shifting into 2’d gear.

My concern is that it could move - maybe I’m unnecessarily worried? I assume it did not shred to pieces as no debris came out during a drain.

 

I don’t know - but the part number changed for some reason - and every failure seems to be in 2013’s with 40-50k miles from what I’ve found.

 

when we first discussed the micro-switch-workaround i wondered about the broken piece in the case as well. i highly doubt that it bouncing around would cause the wheels to lock up while driving, much more likely is if it did bounce up it would just shred itself and maybe damage the mechanism.

transmission shops repair all kinds of transmissions. in the 993 forum some guys re-gear their transmissions. i wonder what is it that is so special about this one that someone won't open it up, take a look and fix it.

 

The prohibitive factor for me right now is a lack of gaskets/seals available on the market to put the transmission back together - and an inability to purchase the mechanism that broke. Porsche does not sell any of these components - and as of today I haven’t found a source to buy from.

I never would have been concerned but for the concerns of the mechanic who diagnosed - he is Porsche trained technician and has been a crew chief for Porsche racing in the past. I’ve taken what he says very seriously as he knows far more than I do.

The Porsche dealer said they cannot say that it was safety concern and cannot say that it’s not a safety concern. Their position was they would need to open up - but they aren’t trained to do that.

 

I understand your concerns and I wouldn't want to take that transmission apart without a manual or some instructions. But you can always cut your own paper gaskets, or use some sort of "form-a-gasket." That type of material is fairly common in production these days. And perhaps the seals could be removed without damage and reused. But it would be a risk for sure. On the other hand--$15,000.

The 991.2 transmission is similar, but it has taller gear ratios in the upper gears and uses a dual-plate clutch, so you might have to replace more components than just the transmission.

 

See the PDK sticky at the top of the 997 forum. Perhaps you can speak with the OP of that thread. The transmissions are similar. Within that sticky thread are a few parts suppliers for remanufactured parts. They might have access to the relevant seals either through OEM or the back door of the OEM factory. The 7 speed manual code ZF 7MT (PDK is 7DT), is also offered by ZF to other manufacturers. Perhaps a white paper or parts list can be had from an inside source at a small car manufacturer.

BTW, thanks for diving into this.