What is the best 915 transmission

[K-Jetronic]

Goodmorning my fellow Pelicans,

Since everyone is always talking about 915 vs G50, I was wondering if there is a big difference between the several 915's that exist. Is there one that is favourable or are the differences negligible. I for instance have a 915/61 in my sc and saw that it was also used in the 911s, 3.0 carrera's and the early sc's with US serial numbers.

Regards,

Gerko Hoek
1978sc

[marcesq]

After '73 boxes are about the same, however, the 915/61 box (which I have as well) has a higher second gear than the 915/63 box which came with the 1980 SC. This means that your car will pull better in 2nd than a comparably equiped 80 or older SC.

[Bill Verburg]

915/67, 915/69, 915/72 are the last & strongest 915s, they also include a factory cooler. Gearing can easily be changed to suit. If selecting a trans from scratch start w/ the best for your purpose, whether it be for lightness or for strength, or a combination.

915/67

[marcesq]

Hey Bill . . . is the oil cooler also on US versions?? Thought they were only on the Euro models.

[Bill Verburg]

915/67, 915/69, 915/72

ROW, but Bruce Anderson once told me he saw a few on some Texas cars.

[marcesq]

LOL . . . somewhere I read that everything is bigger in Texas.

[MRM]

What is the difference between ROW and US 915s? I have an 84 ROW but second gear has been almost munched. I should have a cooler on it, shouldn't I? Is the gearing different for ROW and US cars?

[creaturecat]

row cars came with the cooler fifth gear is slightly higher for some years due to the increased horsepower

[arrivederci]

So for an early car with a 3.6L transplant, the strongest ones are likely the best starting point. Which gearing would you say is best for track purposes? My 7:31 is actually pretty nice for the track right now. With the smaller tires on my car, I never get below 3rd gear and I almost top out in 5th gear on longer straights. But then again, that's with only 170-ish hp. Nowhere near 3.6 territory.

[1fastredsc]

What's involved in maybe trying to put an oil cooler on a 915 that doesn't have one?

[YermanCars]

are these trans easy to find and how much do they go for

[Grady Clay]

What is the availability of the pressure lubed 915 transmissions?

BA says “When these oil pumps were used in the production cars, they were used just to recirculate the transmission lubricant around to be sure that it would provide proper lubrication to all gears.” Everyone should read Chapter 7 in Bruce Anderson’s book (available from our host.)
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© 1996 Bruce Anderson

These were used in RSRs and other 911s.

Best,
Grady

[Bill Verburg]

The cooler pumps Grady pictured were also used on some RSs, All 915 have the bosses etc to mount them. Unfortunately as w/ so much else, they are NLA, last ones I saw went for ~$23300 just for the parts. They also used any internal spray bar



The easiest way to add a cooler these days is an electric sump pump like this, which has the plumbing short circuited temporarily

[KobaltBlau]

That's a neat DIY setup Bill, I haven't seen one like that before. It would be interesting to run a trans. temp sensor to see how hot the fluid gets.

[sundevil64]

Originally Posted by Bill Verburg

915/67, 915/69, 915/72 are the last & strongest 915s, they also include a factory cooler. Gearing can easily be changed to suit. If selecting a trans from scratch start w/ the best for your purpose, whether it be for lightness or for strength, or a combination.

915/67

Bill,

I have a 915/67 cooler and LSD. Any upgrades you would recommend since this is the strongest of the 915's? I don't want to spend the money outside of synchros and dog teeth if the value is not material.

[Schulisco]

Keep in mind that Porsche changed the housing material of the 915 in 1978 from magnesium to silumin/aluminium...the more powerful the engine the more the aluminium case makes more sense...

Thomas

[john walker's workshop]

Aluminum diff housings usually have a loose pinion bearing outer race these days. I see less of that with mag cases. Time takes it's toll.

[-Levi-]

For whatever it’s worth.
My stock 1981 915 with factory lsd had no issues with my 993 3.6 conversion. I did the conversion around 50k miles ago.
I’m in the middle of a 3.8 build and decided to rebuild the box and throw all the good bits at it.

915 rebuild
Wevo Bearing Retainer
Wevo External Shifter
Wevo Solid Shift Joint
Wevo Reinforced Side Plate
RSR Spray Bar Kit
Wevo Internal Gate Shift Kit
Wevo Transmission Mounts
Wevo transmission pump
Setrab transmission cooler
964 axles and machined stubs

[Bill Verburg]

Originally Posted by sundevil64

Bill,

I have a 915/67 cooler and LSD. Any upgrades you would recommend since this is the strongest of the 915's? I don't want to spend the money outside of synchros and dog teeth if the value is not material.

The one big advantage of the last g case trans was the steel girdle that stabilized the shafts, the Al. case trans doesn't have that. A n Al. cas can have one added but the case needs to be machined for it


best place I know of to add the steel girdle is Wevo

or you can add all the little later improvements to the Ng. case version.

It doesn't seem to be much of an issue unless a 3.6 or bigger is used and of course the more miles the more wear of all kinds

[Bill Verburg]

-Levi- did just that, see above

PS Levi any progress?