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Originally Posted by IROC 912
Thank you for the detailed reply Spuggy !
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You're welcome! If I can save anyone 1 or more clutch jobs by sharing, just buy me a cup of tea or an adult beverage should we ever meet
Quote:
Originally Posted by IROC 912
My driving enjoyment is always hampered by the "What If" I launch it hard this time, will the gearbox hold together  |
Hahahaha. I can laugh about it now, but it was a big worry for years...
When you've been through 5-6 clutches and a couple of gearboxes in quick succession, "launching hard" on your eye-wateringly expensive 915 will actually be right at the top of your list of things to avoid at all costs...
Not a new problem; this old thread discusses some of the issues/limits:
http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/774956-915-turbo.html
You should actually be pretty much fine at your power level with a well-fettled 915. Ideally one somewhat stronger than a 7:31 mag 915 without the "standard" strengthening mods (LSD, stiffer cover, bearing retainer).
Which would be more-or-less OK for 300HP. Except if you want to "launch hard", or add significantly more power later. Either/both will still kill a 915 - and SBH G50 or 930 is the only real answer, I think...
It's also worth noting that Jack Olsen runs a mag 915 behind a tuned 3.6 - for years now - in BBII, and doesn't exactly treat it gently. But if you watch his videos, you'll note he has a cooler pump (in addition to the standard goodies), which he switches on when the transmission oil gets close to breakdown temperatures.
I've pondered if uncontrolled oil temps - and subsequent breakdown of the protective film - was what actually did the damage to the original mag 915 - the one with the dark blue 5th gearset & spun bearings - as the PO loved to go to the track and didn't run a cooler.
Quote:
Originally Posted by IROC 912
I keep hoping the 915 will last but now realize it's definitely the slipping clutch that's keeping it together at the moment.
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Sounds likely...
Another thing to bear in mind; Matt (Monson) points out that
all the 915 gearsets are very old now, and should be magnafluxed - or just replaced. Especially the ones that break (e.g. 2nd certainly, ideally 3rd). Modern metallurgy is vastly improved over the 70's...
Quote:
Originally Posted by IROC 912
Need to search the want ads for some g50 bits now and also approach a local custom machining company for some quotes.
Cheers for the data.
Sandeep
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Converted G50s do come up used from time-to-time, just never seem to when you're poised to buy... Or, alternately, about 2 weeks after you start to convert one yourself at ~3x the cost...
Oh, and re-gearing really adds up - but N/A ratios are just stupid low...