915 question

[Sgrun]

Hi,

Will an aluminum case 915/63 fit in my 1972 911 properly?

I know the speedo won't work, but it's a race car so that is not a concern.

Anything else to be aware of? Is the clutch linkage different?

Thanks,
Steve

[MBEngineering]

HI Steve
you can swap the clutch linkage out of the old box into the SC box or change the clutch cable for the SC one, you may need to check the CV/drive shaft joints are the same size, pull the shaft out of the SC box and check if it has coarse or fine spline shafts, if it is coarse the, the old shaft in the car now will swap over and you are good to go,

regards mike

[edbaus]

Mike is right.

The SC probably has the fine spline for the output hubs and the 72 defiantly has the course spline. The issue this can cause is that your 72 probably uses CV shafts with 4 bolts and 2 pins. The sc is set up for 6 bolts. If you have fine spline on the SC trans, then you will have to change the shafts and stub shafts at the wheels to the SC ones. Not the end of the world, just one more thing to do.

The speedo thing is not that big of deal either if you do not mind finding an electronic speedo and wiring it into your car.

Oh, you may need to notch the case on the bottom where the clutch linkage goes through. And as mike says swap the clutch linkage. That swap needs to include the shaft that runs up into the trans to de-actuate the pressure plate. Just held in by a pin, so again no big deal.

Thanks

Ed

[sc_rufctr]

Ed

Is there any value in backdating the clutch on a SC?
Mines OK but the Omega spring and adjustment can be a pain.

[edbaus]

Not really. The helper spring is nice. Not using it just gives a heavier petal feel.

It is a lot of trouble for not a lot of gain and changing out the clutch cable is a horrible job.

But, I did need to do it after melting the one on a 79 930 and nearly burning it and the garage to the ground. Never try to use the clutch cable as the only ground to the motor when you put it in. You are liable to ruin the cable and melt the plastic fuel lines. The rest of the story gets longer.

Thanks

Ed

[sc_rufctr]

I used to own a Fiat 500... Air cooled 2 cylinder 490cc! Non synchro 4 speed gearbox... Driving at its most basic.

Anyway I was working on the egnine and accidental touched the clutch cable with the + wire from the starter motor... And zap... I burnt through instantly with a zap and loud pop. lol... I've learnt to be more careful since then.

[Peter Zimmermann]

Originally Posted by sc_rufctr

Ed

Is there any value in backdating the clutch on a SC?
Mines OK but the Omega spring and adjustment can be a pain.

In my opinion backdating is the worst thing that you can do. The clutch adjustment is not a difficult process, it just must be done in the correct order. Follow the procedure outlined in the factory manual, after a couple of times you'll say, "Hey, I get it!" And the clutch will be wonderful for both street and track use.

FYI: I can't remember seeing coarse spline axle flanges on a 915/63, so you're probably going to have to get creative with the CV joints.

[Sgrun]

If I swap the diff over from my 72 into the newer case, then the spline issue goes away - correct??

Steve

[edbaus]

Peter is going to jump on this one.

You would need to keep the ring gear with the transmission. The ring and the pinion is matched.

You can do this, but you have to set up the backlash on the ring and the preload on the bearings. Much harder than changing out the half shafts.

Now, there is one easy, and maybe a little odd to do, but you can have a hybrid half shafts. Have the outer CV an early one and the inner CV joint a later one. Odd, but it would work. Not my favorite solution to this.

Ed

[Peter Zimmermann]

Originally Posted by edbaus

Peter is going to jump on this one.

You would need to keep the ring gear with the transmission. The ring and the pinion is matched.

You can do this, but you have to set up the backlash on the ring and the preload on the bearings. Much harder than changing out the half shafts.

Now, there is one easy, and maybe a little odd to do, but you can have a hybrid half shafts. Have the outer CV an early one and the inner CV joint a later one. Odd, but it would work. Not my favorite solution to this. Ed

LOL!

The amount of work involved with moving a 7:31 R&P into a later gearbox makes your axle solution more and more attractive! I've never done that large/small CV on a single axle, but I can't see a reason not to. If the width of the SC CV is the same as the early CV, and the splines are the same, give it a try!

[Sgrun]

Yes, the intent was to move the 7:31 R&P out of the dreaded 72 case anyway, so that amount of work is a given.......

Thanks,
Steve