Clutch Spline Question

I have a 901 transmission, off a 69 911T, which is mating with a 2.4S engine and I have already installed the later 2 piece flywheel. To match, I have ordered a 72 225mm pressure plate/clutch combination. A similar 225mm plate/clutch is available for 70-71 models which have the 901 tranny, but at a higher price, which is why I chose the 72 version. 72 is the year the 915 transmission began. Is there a difference in clutch spline size between the 901/915 transmissions, if so I should probably get the 70 version. 69T has a 215mm clutch mated to a one piece flywheel.

Thanks,

72 and later have a different spline for the type 915 transmission and wont work for 70-71. Also a 69 trans needs a 215 clutch and flywheel because it lacks the provisions for a 225mm clutch.

The engine doesn't care what flywheel/clutch you use.
The transmission cares a lot.

Trans, not the engine determines flywheel and clutch type.

Because of the release fork and pivot you're stuck with using the 215mm flywheel and clutch. If it's a race car we make an alum flywheel that uses a 5.5" single or 2-disc clutch. If its a street car go with a Kennedy pressure plate if you're concerned with clamping pressure.

Quote:

---

Originally Posted by 66S

72 and later have a different spline for the type 915 transmission and wont work for 70-71.

---

Get it, 915 clutch won't work in 901 trans.

Quote:

---

Originally Posted by Frank Beck

Because of the release fork and pivot you're stuck with using the 215mm flywheel and clutch. If it's a race car we make an alum flywheel that uses a 5.5" single or 2-disc clutch. If its a street car go with a Kennedy pressure plate if you're concerned with clamping pressure.

---

Thanks but that is not music to my ears, unfortunately. How do the 70-71 avoid interference using the 225mm clutch since they use the same 901 trans ?

Quote:

---

Originally Posted by JPM

How do the 70-71 avoid interference using the 225mm clutch since they use the same 901 trans ?

---

It's not an interference issue, it's a clutch compatibility issue.
A 69 transmission is set-up for a push-type clutch, a 70/71 for a pull-type clutch. That's what Frank is referring to by "release fork and pivot".

A 69 transmission is a 901, a 70/71 is not.

Jon B.
Vista, CA

I get it on the push/pull versions of the 901 trans, but what do others do about adapting bigger engines to their early 911's, other than the Kennedy clutch suggested by Frank.

Quote:

---

Originally Posted by JPM

I get it on the push/pull versions of the 901 trans, but what do others do about adapting bigger engines to their early 911's, other than the Kennedy clutch suggested by Frank.

---

If the engine has a 6-bolt crankshaft, use an early flywheel and clutch (65-69 or 914/6) with your 69 transmission.
If you want to use a later flywheel and clutch, you need to use a later transmission or re-case yours.

Jon B.
Vista, CA

Okay thanks guys, I guess I'll have to use my early flywheel and clutch. Save some cash too.:)

Just an update in case this can benefit anyone else. When dealing with earlier transmissions like the 901/911, the problem lies in the weak first gear. Some have solved this by converting to a 4 speed with tall ratios and according to Kennedy, with a V8, get rid of first gear and change the ratios of 4th and 5th to make it a 4 speed.
So you are faced with breaking 1st gear with too much pressure or slipping in 1st with too much power. I have decide to follow Frank Beck's suggestion and take a chance with the Kennedy stage 1 pressure plate which ups the clamping pressure from 180 (stock) to 230 ft.lbs of torque. Thanks all for weighing in on this.