915 in a G50 chassis ?

[lrodri64]

Hi !
Just trying to help a friend.
It is possible to install a 915 in a 1987 cabrio 911?
Any idea of how difficult would be?

Thanks.

[Drisump]

I guess most things are possible but it's going to be a lot of work and money. Changing the pedal cluster, removing all the hydraulics, installing the cable hardware, sourcing all the stick linkages and last (but certainly not least) dealing with any suspension/ chassis problems. Myself, I have a 915 car and I like it but the market LOVES the G50. Even if the 915 is a much cheaper alternative for you, the cars resale value would be far less. Most people inquire about the reverse procedure (putting a G50 in a 915 car) to get a more modern feel and "power headroom", but when all the effort and money is tallied up, you might just as well sell the 915 car and buy a G50 one. Cheers

[KTL]

The G50 is longer and that's why the Porsche designers had to modify the torsion bar tube to let the tail case of the trans fit in that area. So since the 915 is shorter, it'll physically fit no problem. Just need to use the 915 trans mount crossmember. Give Porsche credit for keeping the bolt spacing the same for the trans crossmembers!

Also need to source a 915 clutch assembly since the G50 clutch is a different size and is operated by hydraulic slave like Drisump said. You need a typical 915 clutch & release bearing and the '84-'86 Carrera flywheel in order to make things work in the '87

As far as suspension, it's a non-issue. Putting a G50 into a 915 car presents suspension problems (torsion bar housing clearance) if one does not shorten the G50. However doing the reverse by putting a 915 into a G50 is no problem with suspension. No changes needed.

The actual work of installing the 915 is not that hard. Pedal and cable installation is straightforward since the G50 chassis uses the same mountings for that stuff as did the earlier 915 chassis. Shifter swap is very simple too. All bolt in swapping.

Have to change the trans mounting studs on the engine case as well, since the lengths are different. Nothing difficult there.

One challenge may be the drive flanges on the 915 you choose. The G50 uses 108mm dia. drive flanges with M10 CV bolts. Most 915 (except mid-1985 thru '86) use 100mm flanges with M8 CV bolts.

Will also need to make sure you get the speedometer sending unit with the 915 (mounts on transmission case) because the G50 speedo sender is different.

[Nick Triesch]

Why would you want to do this? The G50 is a normal modern quick shifting tranny. You just get in the car and shift it. With the 915, you have to think about how you are going to shift it.

[Matt Monson]

I'm going to guess that the G50 needs a rebuild and this is perceived as the cheaper solution to the problem. If so, it will neither be cheaper nor easier, especially if the owner is not a diyer.

[KTL]

Only way I see it being worthwhile from a cost standpoint is if you have a car missing the G50 and you already have most of the 915 stuff on hand/lying around. like it's "free"

Wirth respect to the benefit 915 vs. G50 its a wash IMO. Put a spring centering shifter in a 915 (one that is not overly worn/abused) and it's a very nice trans. I started with a G50 street/track car and currently have a 915 in the racecar. I've never found the 915 a liability. Once I corrected some shifter deficiencies, it's been a fantastic trans. Shifts very quickly and reliably.

[Nick Triesch]

The 915 is kind of like shifting a farm tractor.

[Matt Monson]

Originally Posted by Nick Triesch

The 915 is kind of like shifting a farm tractor.

If one knows how to rev match and double clutch it's like driving a dog box with less clunking. I've been driving my 912 all week and I'd forgotten just how much I love driving a 901 gearbox. It's like beer, an acquired taste.

[KTL]

Well the G50 ain't exactly the cat's meow nowadays. I recall getting into my '87 Carrera after having driven a 2001 BMW 5 series manual 6 spd for a long time (my former daily driver) and man I was lost for a little while. G50 gate selection was very narrow and not all that communicative compared to the BMW. Point being, I think we adapt and get used to things

[1982911SCTarga]

Originally Posted by Nick Triesch

The 915 is kind of like shifting a farm tractor.

You mean like a John Deere 4020 with Syncro-Range and not a Powershift, right?

Brian

[Nick Triesch]

I can drive my old 911 just fine. But in the last 3 years only 3 other people have driven it. They all said "What is wrong with the transmission?" And I gave them the proper answer, " They are all like that. " I remember years ago when my friend bought a super clean 84 Carrera with only 74,000 miles. He let me drive it but 1st gear did not seem to work no matter what I did. I asked him why did it not shift right. He answered, " The Porsche shop said they are all like that". The shop told him that if he did not like it he should buy a newer model with the G50.

[Peter Zimmermann]

Good grief; what a project! Does anyone know if the '87 car has an unused tube, in the tunnel, for the clutch cable that a 915 would require?

To the OP, what's wrong with your friend's G 50?

[lrodri64]

Thanks for all tips. It is not mine, it's a friends 87 and he has a 84 power train to install.
Thanks again

[SilberUrS6]

Originally Posted by Nick Triesch

The 915 is kind of like shifting a farm tractor.

Not like any farm tractor I ever shifted. It's not as automatic as modern hydraulic-clutch cars, but it's pretty darn nice compared to the tractors and farm trucks I used to drive.

[Porsche84]

Irodri64

As Kevin Mentioned, if you have the 87 half shafts, you need the drive flanges for the 85-86 915. I have some of those. If you are doing an 84 engine trans swap, you may have the 84 half shafts, which will work with the "SC type" 100 mm flanges. I have other parts for 915 if you get stuck, but no shifter parts. Do the work installing all new bushings etc. and the 915 will work fine.