Differential: are those gears worn? check the pics

[911cedric]

Hello,

my 993 turbo as the noisy first gear symptom;
loud whining while driving in first gear; only stops when disengaging the gear in neutral. According a friend who listened under the car while the wheels where spinning, the second gear might me a tad noisy too at low RPM.
I already teared apart the gear box without finding anything that might cause this noise;

i found out that the dog teeth on first and second gear were worn,
forks of 1/2 and 5/6 were worn and had some play.
guide sleeve of 1st and 2nd gears was worn

i replaced all those item with new synchro rings, including first and second gear wheels, but not the gears from the primary shaft. (the first gear wheel on the primary shaft is made of one piece with the shaft)
it seemed to me that when i checked the gear wheels, that they were not worn on both sides (primary / secondary)

well, i replaced all these without any improvement.

some guys around told me that the primary shaft with the first gear wheel might be slightly bent, but i didn't see any visible damage.

Some others suggested that my DIFFERENTIAL my be worn;
today i teared apart the differential and here is what i found: check the pictures
i don't have a huge experience of gearboxes and differentials, but it seemed to me that those planetary gears are worn. I had some steel coppers in the housing.

I found out that the planetary gears set as pairs on the two guides/shafts had some axial play; i don't know if it's normal.

I will replace the primary shaft of the gearbox to make sure, but i don't know what to do with this differential. The problem is that if i replace the gear set, i read in the workshop manuals that some tunings need to be performed; and i don't have this kind of equipment.

Please let me know what you think of those pictures

[Grady Clay]

911cedric,

I do not see anything unusual with the differential gears.
The differential gears would only operate (and make noise) when one wheel is turning faster than the other wheel.

Please post images of the ring gear and pinion gear.

Please post images of the first gears.

Have you inspected the bearings under the free gears?

This may not be the best forum for 993 but all Porsche transmissions are similar.

Best,
Grady

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911cedric,

Je ne vois pas quelque chose d'inhabituel avec les engrenages différentiels.
Les engrenages différentiels ne fonctionnent (et font du bruit) quand une roue tourne plus vite que l'autre roue.

S'il vous plaît envoyer des images de la couronne et le pignon.

S'il vous plaît envoyer des images des premiers engrenages.

Avez-vous examiné les paliers dans les engrenages gratuitement?

Cela peut ne pas être le meilleur forum pour les 993, mais toutes les transmissions Porsche sont similaires.

Best,
Grady

[Matt Monson]

Hello Cedric,

Your differential spider gears look fine.

As for your noise? If you changed the idler gears on an older car and didn't change the mainshaft at the same time, you likely made the problem worse. The original gears had worn into a pattern with the gears on the shaft. When you put in different gears, they did not have the same wear pattern as the original. On a 993, 1st and 2nd gear idlers should always be replaced with a new shaft at the same time.

regards,

Matt Monson
Guard Transmission LLC

ps. the guy who told you he thought your mainshaft was bent was Paul Guard, my business partner.

[911cedric]

thank you all for your support

FYI here are the pictures of the gear wheels, second gear, and then first

they do not look so bad as you will see except the dog teeth

[911cedric]

regarding the differential gear wheels,
they seem to me a bit worn and blued in some places.

i will replace the primary shaft this week end; i hope i won't have any surprise with this differential thing.