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I have this low mileage perfectly nice 1998 993 6-speed transmission, G50.20 with a clutch fork pivot shaft boss that is cracked.
Had this in a tube frame chassis car, pulled it when installing a much stronger motor (270 rwhp switched to the new estimated 550-580 rwhp - dyno next week). Installed a G96.50 instead with that motor to avoid abusing this G50.20 gem.
Discovered that the pivot shaft boss has cracked on the G50, common outcome of overtravelled slave . It looks like it has been previously bandaid repaired.
Has anyone had success fixing these?
Got someone with a lot of transaxle familiarity recommend to tap and helicoil for a little larger bolts.
Someone else mentioned alu weld but did raise concern about safety in doing so due to oil residue inside the transmission.
Another is something like a CMS billet boss repair kit, but that requires opening the trans and it seems incredibly unnecessary to open this otherwise pristine trans.
Would be interested in feedback from those who have actually been resolving this type of pivot shaft boss issue.
Here's an old thread on Pelican that dealt with this same issue. Looks like CMS cut the boss off and re-welded a new one on. The revised method seems to be cut off and bolt on new vs welding.
Yes, just drain the oil from the gearbox and TIG weld the piece back into place. BTDT - see here. The fix has ~100K miles on it... You are lucky that everything is pretty much still there. If not, the other option would be to use a graphite EDM rod and build up a BOSS in place. And then use the special Porsche tools for aligning the holes; special tool kit #9292, Porsche PN 000 721 929 20. Which consisted of an assemble cutter (9292-1), arbor/guide (9292-2), guide piece (9292-4), spring and guide pin (9293-3).
A friend with a '95 993 track car, mostly stock HP / reduced gears - had this happen, sent it out to CMS, has worked fine and held up to 20+ HPDE weekends since then. Allow enough time for trans pull / disassembly, shipping, repair, and shipping, and reassembly, re install. Months...
Yes, just drain the oil from the gearbox and TIG weld the piece back into place. BTDT - see here. The fix has ~100K miles on it... You are lucky that everything is pretty much still there. If not, the other option would be to use a graphite EDM rod and build up a BOSS in place. And then use the special Porsche tools for aligning the holes; special tool kit #9292, Porsche PN 000 721 929 20. Which consisted of an assemble cutter (9292-1), arbor/guide (9292-2), guide piece (9292-4), spring and guide pin (9293-3).
This sounds like the most natural way to go, everything is there so doesn't look too advanced for someone very good at welding.
A friend with a '95 993 track car, mostly stock HP / reduced gears - had this happen, sent it out to CMS, has worked fine and held up to 20+ HPDE weekends since then. Allow enough time for trans pull / disassembly, shipping, repair, and shipping, and reassembly, re install. Months...
Trans is out and I don't need it anymore so time is not a factor. But possibly want to repair it to have a spare for some future project.
The CMS repair is neat, the old boss material gets cut and all you have if the bulkhead/cast so makes it look nice and clean. The caveat is that I am very against opening a perfectly smooth low mileage box.
Going to lift this: Does anyone have a really solid reliable contact in the Bay Area who is able to perform a quality job to repair the cracked boss (and possibly reinforce the not broken one)?
09-03-2021, 12:47 PM
G50.20 clutch fork pivot shaft boss fix
. It looks like it has been previously bandaid repaired.
