915 Transmission Identification

SuperNovaSS · 03-16-2018, 08:28 AM

I hoping someone can help me ID this trans. It was recently found on a storage locker that was sold due to back rent. The locker was full of mostly 60's American muscle car parts this this trans being the odd duck of the mix. All the other parts were very nice and desirable parts so the owner of the locker did not seem to save junk. I plan to sell this transmission but it is tough to to without knowing what it is.

I have done some Google searches and found the location of the important stamped numbers. Unfortunately, this area is right on the bottom of the trans and it appears to have been scraped on the ground a few(or more than a few) times. As you can see in the pictures below, the only numbers that can still be seen are "15/6" and "8181". Based on the 15/6 number, I believe the trans could be a 4 speed or a 5 speed. I removed the inspection cover on the underside and tried to snap a few pictures of the internals. The oil looks clean and I don't see any chipped teeth or damage. Is the 5th gear visable in the pictures? If it possible to figure out what this is by counting a few sets of gear teeth to determine a few ratios?

Thanks!

Jason

SuperNovaSS · 03-16-2018, 08:29 AM

A few more pictures of the whole trans.

Thanks again,

Jason

kevingross · 03-16-2018, 10:16 AM

I believe you're missing a couple of characters from the "15/6". It should read "915/6x" where the 9 is a given, the x is unknown. A list of codes here: Blue Sky. Aluminum case per photos, which is consistent with it being a post-'78 transmission. Cheers,

SuperNovaSS · 03-16-2018, 10:36 AM

Kevin,

Thanks for the reply. Yes, I am aware some key numbers are missing. I was wondering if there is another way of IDing the trans such as counting gear teeth to determine ratios.

Thanks again,

Jason

SuperNovaSS · 03-18-2018, 08:00 PM

Does anyone have an idea how to ID this trans other than the numbers on the belly?

Thanks,

Jason

Mark Salvetti · 03-18-2018, 08:19 PM

On my 1979 (that was built in September 1978), the nose piece has a year cast into it. In my case it is 78. If you are looking at the nose piece the date is at about the 9 o'clock position. That might help you narrow things down a bit.

Fifth gear is under the nose piece section. You can't see it without removing the nose piece.

Mark

SuperNovaSS · 03-18-2018, 08:59 PM

Quote:

Originally Posted by Mark Salvetti

On my 1979 (that was built in September 1978), the nose piece has a year cast into it. In my case it is 78. If you are looking at the nose piece the date is at about the 9 o'clock position. That might help you narrow things down a bit.

Fifth gear is under the nose piece section. You can't see it without removing the nose piece.

Mark

Thanks Mark,

I will check that out. The year may help me figure out what the 915/6x code is. I’ll report back for those who may be curious.

Thanks again,

Jason

Flojo · Flojo's Garage

any chance to find out what 11-type it was in or to what engine it was coupled?

could be a 915/61. that was my code on a 01.1979 SC, built 11.1978

but it could be as well a 915/63 from an early Carrera 3.2

SuperNovaSS · 03-19-2018, 07:44 AM

Unfortunately, I don't have a way to know what it came out of. It was in a storage locker that was sold due to back rent and this was the only Porsche related part in the whole locker. Most of the parts were for 60's American muscle cars.

Thanks,

Jason

gshiwota · 03-19-2018, 07:55 AM

Looks like a later model trans. Most likely a 5-speed as 4-speeds were discontinued in 77 and they were rare items to begin with here in the US. That's an aluminum trans with electric speedo and looks like it's from a 3.0 SC not a 3.2. I don't see the notch for the ref / speed sensor.

So my guess is it's a 5-speed trans from 1978-1983.

Matt Monson · 03-19-2018, 08:01 AM

Measure the axle flanges. 100mm SC, 108mm 3.2 Carrera.

Peter Zimmermann · 03-19-2018, 12:06 PM

Allen wrench required to remove the drain/fill plugs. Electronic speedo connection. Aluminum housing. No flywheel sensor cut-out. This all adds up to a 1980-1983 3.0 911SC, which would be a 915/63.

Matt Monson · 03-19-2018, 12:22 PM

Didn't even look for the cutout...

SuperNovaSS · 03-19-2018, 02:12 PM

You guys are amazing! Thank you very much for all the help. Any idea on the value of the puppy? Although I don't see any damage, it sounds like these transmissions are problematic and this should be viewed as a core that needs rebuilding. I see prices all over the board for these.

Thanks again,

Jason

yelcab1 · 03-19-2018, 02:56 PM

I would consider any 915 gearbox that is sold without any records to be a rebuildable core. If I were looking for one, I would not pay more than $1,000. Until you open it up, you don't know what needs rebuilding and it is getting very expensive to rebuild one totally now.

For example, I have never seen a 915 gearbox where the outer bearing race did not come out of the middle bearing support housing. That repair alone is $1,000

SuperNovaSS · 03-20-2018, 08:35 AM

Thank you. I'm used to dealing with Muncie 4 speeds out of 60's GM cars. Rebuilding a Muncie is generally $250-$300 plus a $80 small parts kit. Gears are inexpensive as well. This is a whole different world. Thanks again for the education guys.

Jason

Matt Monson · 03-20-2018, 09:03 AM

A $1000 core 915? I’ll buy 5 at that price. They are 2-3 times that these days. They all need machine work to fix the bearing these days, and it’s not usually $1000. CMS does it for $150 per bore.

It will take you 15 Minutes to pull that sidecover. Then you can photograph the condition of the ring and pinion. If that is verified good it will lock in those values I mention above

SuperNovaSS · 03-20-2018, 09:13 AM

Excuse my ignorance. When you say pull the side cover, do you mean the large round cover behind the driver's side axle flange? If I pull that cover, is there and mechanical setup in order to reinstall it or is it just remove and reinstall?

Thanks,

Jason

OhioRick · 03-20-2018, 09:43 AM

I've been knee deep in my 915 transmission rebuild for the last couple of months and that looks exactly like my 1983 911 SC 5-speed tranny which is 915/63. Mine also says 74D with serial #0634. Too bad yours is ground off. Hopefully, it didn't happen in an accident.

Yours has the magnetic speed sensor, like mine, so I would say about the same age as mine. I believe there is a date code box cast into my center section of the housing on the side with the big removable cover (on the upper side). As someone else said, check diameter of the hubs to help pin it down further.

Matt Monson · 03-20-2018, 09:50 AM

Quote:

Originally Posted by SuperNovaSS

Excuse my ignorance. When you say pull the side cover, do you mean the large round cover behind the driver's side axle flange? If I pull that cover, is there and mechanical setup in order to reinstall it or is it just remove and reinstall?

Thanks,

Jason

You remove both axle flanges. Then you pull all the nuts around the perimeter. You won't be disturbing anything. You will find the differential inside with bearings on it. The ring gear will be bolted to it. That's what you want to inspect.