choosing a 915 transmission

[NCbug]

hey i found a place thats selling 915 trannys and i have the choice of the following years (1972-1973) , (1974) , (1975-1976) , (1977-1979) , (1980-1983) , (1984-1986) , (all turbos) . which kind is best and why ? or are they all the same?


thanks alot

[Wally]

Hi NCBug,
A lot has been said on that subject (too much sometimes...) in this forum, do a search for 915 or so.
In short: As of '77/'78 ?(3.0 SC engines) the cases were alu as they were magnesium before.
Also, I believe LSD was option or standard on some versions. If you want that, now is a good time to look for them.

IMHO, the most important thing to look for, besides the tranny being as in good a condition as possible, is the diameter of the output drive shafts.
Most are 110mm, which makes it impossible to use VW splined axles.
Some (early?) versions have 100mm output CV flanges, which make it very easy to bolt it to a (Bus) 100mm VW CV and subsequent axle.

I use a 915/40 trans from 1976 (2,7ltr model) which has 100mm output flanges

Greetings,
Walter

[Michael Ghia]

NCbug,
There are basically 3 different types of 915 tranny.
The early ones have a mechanical speedo output and suffer from the input shaft seal (which is also the support for the clutch release bearing) pulling out and then you get oil everywhere...
It has 94mm PCD output flanges.
1972-1978 ish...

The next one has an electronic speedo output, looks similar to the early one but has the problem fixed with the input shaft seal, comes with 944/T2 output size flanges and comes in the 911SC.
1978-1983

The last one came in the 3.2 911 and has an oil cooler so is pretty easy to spot. It is the best of the lot as Porsche had ironed out all the probs. Output shaft size on this I can't remember as they're pretty rare.
1983-1987

The 2 earlier 915 trannys suffered from 5th gear seizing onto the shaft after very high speed long runs hence the oil cooler which dumps oil straight back in over 5th gear.

After 1987 the G50 came out and things were never the same again

Oh, the Turbo never used a 915 tranny, they had a 4 speed 930 capable of handling 800bhp!

MG

[verbeekb]

Make sure to check the number of gears, there are 4 speed 915s, although a very rare factory option, I ended up with one as a replacement in an early 3.2, imagine the look on my face and the new words I Invented when I tried to shift to 5th during the test drive after installation ...

[boygenius]

I thought only the 930 transmissions were 4 speed...

[verbeekb]

well.. so did I ..

[Wally]

No, he's right!
AFAIK, with the 2,4 and 2,7 ltr models it was still 4-speed as standard and 5-speed optional. Most all got the optional 5-speed as we know now.

For instance I once had a 915-12 coded trans and those are 4-speed for sure, so look uo the type number in a list before you want to buy a magnesium cased 5-speed 915 trans...
Unfortunately, the type code is a the lowest point of the trans and is sometimes grinded of with lowered cars or towing/dragging the trans around the salvage yard ground.

Greetings,
Walter

[boygenius]

Well I learned something today. :agree: