mark_in_maine

Hi All:

I have decided to start a new thread versus continuing the existing thread titled New starter Woes since the subject matter has clearly changed. Sorry if this seems like a long post for a relatively simple question.

To recap, its a 91 c2 cab with a tip transmission. Car originally went in to the shop to have a new ignition switch installed since the one that had been installed about 2 years ago failed. The failed switch would keep the starter engaged unless the key was turned counter clockwise slightly. The car was never allowed to run with the key engaging the starter except for perhaps a few seconds at a time until I figured out that turning the key back slightly would disengage the starter. After the installation of the new ignition switch the car was started several times and all seemed great. The shop owner himself went to test drive the car before returning it to me and switched on the ignition only to hear the starter spin without engaging the engine. After several checks of many things it was decided to remove the starter which showed that it was very worn and it was decided to replace it. The new starter was ordered and installed only to have the same symptom happen. Starter spins but wont turn the engine over. A removal of the starter and a hand inspection using fingers has now confirmed that the ring gear spins freely around the flywheel and will not engage the flywheel to turn the engine over. I am told that the ring gear has been inspected with a camera and looks fine and that there is no sign of cracks, shavings or metal debris etc. The motor and transmission are now out of the car and about to be separated. My question is relatively simple I think. How is the ring gear attached to the flywheel in a tiptronic transmission application? Heated and pressed on? Bolted on? Is there an electronic clutch of some kind? Is there any feature or situation conceivable that the tiptronic transmission may have that would allow the ring gear to spin freely? Anyway, sorry for the long post as you can see I am at a loss here. I have searched the archives for several days, but find nothing that really definitively discusses the flywheel setup/failure in a tiptronic application. Any help would be appreciated. Thanks

darth

weld it back on.

mark_in_maine

Update:

As of an hour ago I visited the shop and saw the ring gear spinning freely on the torque converter. The ring gear is mounted on to the torque converter in a tiptronic application. NO metal debris, metal shavings etc were found when the transmission, engine and torque converter were separated. So after a little discussion and much lamenting about the situation it was decided to make some welds (shop owner is a master welder) and attach the ring gear to the torque converter to solve the problem. The other solution would have been to source a new tip torque converter which it as decided not to since there has been no transmission related driving issues...yet!! I took a couple of pictures of the torque converter with ring gear which I will post later on for future reference. I also managed to find one post over on the pelican parts forum where a tip ring gear had failed. The resolution to the situation was never posted but I suspect the converter was replaced.

Metal Guru

If they don't get the ring gear welded onto torque converter straight with minimal lateral runout the starter gear may not be able to disengage from the ring gear.
Part number is 943-316-001-00 if you decide to go new.

mark_in_maine

A picture of the torque converter with failed ring gear. The ring gear has no play and does not move forward or backwards on the converter, but it can be spun around the converter.

mark_in_maine

Another picture of the converter from the side.

mark_in_maine

Metal Guru Thank you for your feedback and the part number. I will pursue that angle as well.

mojorizing

Mark,
Is the ring heat shrunk on the converter? What precautions are you taking on welding the ring to the converter? TIG welding it? What do you contribute to this failure?

I find that the ring gear/ converter are one part number kind of disconcerting. It's not meant to be opened up and rebuilt?

Metal Guru

Torque converters are brazed or laser welded together. If an auto transmission gernades, the torque converter has to be replaced, along with things like the valve body.
The Porsche design is unusual to say the least. Most auto transmissions use a flex plate in place of a flywheel. The flex plate has the starter ring gear welded to it and it's only purpose is to engage with the starter pinion gear and turn the engine over.

mark_in_maine

Mojo:

Metal Guru is correct the 964 converter is single unit. I have been told when they are rebuilt, the converter unit is split apart on the weld seam using some sort of lathe so the unit can be opened up.

It is difficult to say exactly how the ring failed. I was clearly having a problem where the ignition switch mechanism was keeping the starter engaged with the ring. This was only for a few seconds at a time (ok maybe 8-10 seconds the first time it happened). After 4-5 starts where the engine would run for 5 seconds or so with the starter still engaged I figured out that I could manually turn the key back enough to disengage the starter. It went to the shop to have the ignition switch replaced and the ring failed while they were testing the new ignition switch. Whether or not the starter being engaged with the ring gear while the engine was running for a few seconds at a time caused enough stress on the ring gear to cause the failure is still a great question. Anyway, that is story from Maine. Will post the outcome when all is said and done.

Dsqr964

Mark, was wondering how your repair and rebuild came out. -D²

mark_in_maine

Dsquare

The starter ring gear was welded back to the torque converter and the motor was reinstalled. I have driven about 1000 miles or so since then with about 50-60 starts and all seems to be okay now. Still a very strange situation as no one I have talked to has ever heard/seem this happen before. All in all including a new starter, new ignition switch, various diagnostics, welding the ring gear and dropping the motor in and out with fresh fluids and filters etc it came to just under 1800 bucks. Pretty expensive considering the car went there to get a 60 dollar failed part (ignition switch) remedied.

Best regards

HBP

I realize this is an old thread but just started having the same issue with the ring gear slipping on the torque converter. 1997 993 C2S Tip This is the only thread I could find, seems like a very rare issue.

Anyone know how the OP's fix held up or have any opinions on having the ring gear welded? Talked with the local indie and he didn't think welding would be a viable option, worried about the torque converter going out of balance and eventually damaging the input shaft on the transmission.

Thanks

No_snivelling

Have you given any thought to using a Loctite product? If your ring gear is like the OP's ring gear and has no radial play then I would at least investigate this option. Call their tech support number and if they cannot confirm it, ask for the product with the greatest shear strength and ask what the shear strength is. With that number you can calculate what it would take to shear the entire bond line between ring gear and torque converter. The bond line would have considerable area so it might withstand the shear forces of a starter motor.

You would want the parts super clean and also use the appropriate Loctite primer first. Just my 2 cents worth.

JohnK964

Loctite Green Sleeve retainer that stuff is almost impossible to loosen if the gap is tight enough