901 Transmission/clutch

Mat 71 · 09-08-2005, 07:25 PM

Does anyone have any info re: this transmission/clutch? I am putting this back together (I didn't take it apart) on my '71 911T and assume that it is a 901 trans? It bears the numbers 911/01 and then 7114435 under that number.

I think that it is a push clutch as well, as the fork does not attach to the throwout bearing. I would like to see a picture of how the cable attaches to the transmission/fork etc... as I think I am missing parts.

Any help from anyone is greatly appreciated.

Thanks.

jluetjen · jluetjen's Garage

Actually, you have a 911 (The number is a give-away) gearbox where the clutch fork will be attached to the throw-out bearing. It also uses the later style flat flywheel as opposed to the earlier dish-shaped flywheel that the 901 gear boxes used.

john walker's workshop · 09-09-2005, 07:39 AM

70/71 only with a pull clutch.

Mat 71 · 09-10-2005, 10:55 AM

Thanks for the responses. I am however still stuck. There is not a spot to attach the fork to the throwout bearing?? The fork has a groove on one side and the throwout bearing is very different than the pictures I have seen (has two tabs). Also, the cable end of the fork appears to be facing to be a push clutch and not a pull. Anybody have any thoughts?

jluetjen · jluetjen's Garage

Those two tabs on the throw-out bearing need to be parallel to the fork when installing the transmission. Then you need to take a screw driver (as well as some fiddling with the fork) and rotate the bearing so that the tabs are perpendicular to the fork. This engages the fingers of the fork with the throw-out bearing.

Samuel1975 · 12-03-2021, 11:04 PM

Hi, it is possible to use this gearbox with an 912 engine? Thanks. Samuel

gled49 · 12-04-2021, 02:39 PM

Not without modifying the release system from pull to push type clutch.

Mark Henry · 12-05-2021, 12:53 PM

Somewhere I have an old PP and bearing for the 911 transmission.

Quote:

Originally Posted by Samuel1975

Hi, it is possible to use this gearbox with an 912 engine? Thanks. Samuel

If you're a good fabricator you can always make it work... I have a 911 transmission in my '67 VW bug. It has a modified, bent, cut and welded bearing fork to make it do what I wanted.

stownsen914 · 12-05-2021, 06:22 PM

The trick using this on a 912 is that it requires use of the later style 911 clutch (plus the 70/71 only throwout bearing). The challenge there is that style clutch was never used on the 912, so there's no flywheel available unless you have a custom one made. Or as Mark suggests, make a custom throwout fork to work with the regular 912 clutch setup.

Mark Henry · 05:14 AM

You could use a early flywheel, PP and push TOB then mod the fork to work, this is how I have my T4 914 engine set up in pull configuration with a 911 trans in my bug. The 914 T4 flywheel, is the exact same as the early 901 fly, except for the crank mounting.

If the OP needs a 911 pull style TOB I do have a good used one. I also have a PP but it's aluminum and the edges of the friction surface plating is starting to peel off.

Long Nose · 12-21-2021, 01:47 AM

Just installed a 901 transmission with the push clutch, found this diagram from a German workshop manual I found on line, was very helpful. I can post some pictures of the install, as it is still on jacks...

Long Nose · 12-21-2021, 02:01 AM

I found that taking that clutch fork off the transmission and just test fitting with the throwout bearing was helpful, just seeing how it fits. There is a small notch in the back of the throwout bearing that the fork sits in when you get it right. Takes a little fiddling and trying to figure out how it works when you are trying to mate the transmission to the engine is hard because you can't really see inside the bell housing. It's a pretty tight fit and the input shaft has to be lined up almost perfectly straight for it to all fit together.

I guess there are not that many transmissions out there with a push clutch since they only did it from 1970 and 1971. However, from my understanding the 901 transmission was used in the 912 also, so that transmission would fit a the 4 Cyl 912 Engine? I am a little confused by the transmission in the picture, as this is a 911 serial number, so is that a 915 transmission?

Wasn't there a 912 produced for MY 1976? Wouldn't that have used the 915 transmission?

Mark Henry · 12-21-2021, 04:38 AM

The 901 came in a few variants the 901, 914 and 911 are all basically the same 901 transmission just configured (nose cone, mounting, etc) for different cars. The 911 trans case is a bit different as it has an offset on the fork pivot point.

Ed911S · 12-21-2021, 05:58 AM

Use pressure plate and T/O bearing for type 911/01. Before you slide trans on, check that there is a spring plate behind the fork on pivot bolt. Turn T/O bearing so it slides past the fork when you install trans and tighten nuts and one bolt on trans. Pull fork toward trans and turn the T/O bearing until it the two plates align with the humps on fork. Easy peasy

Clay Perrine · 10:49 AM

There are two types of clutch used with the 901 transmission. 1965 to 1969 used a 215mm push type clutch. This was also used in the 912 the 914 and later in the 912E with a special 915 transmission. 70-71 911 used a 225mm pull type clutch that is like the later 915 clutch (But not the 912E). The throwout arms are not interchangable between the 65-69 and the 70-71 transmissions. You can't retrofit the 69 and older arm to a 70-71 transmission. The pivot point was moved in 70 to work with the pull type clutch.

The throwout bearing and pressure plate is specific to the 70-71 911. It does not have the same pressure as the later 915 pressure plates because the pivot point for the throwout arm will pull out of the transmission case if you use a 915 pressure plate. The throwout bearing is unique to the 70-71 911, and is well over $300.00 to get a new one.

When you work the clutch on a 69 911, the cable case is anchored and the cable pulls the arm to the front of the car. This pushes the throwout bearing into the pressure plate, disengaging the clutch. In the 70-71 911 , the clutch cable is anchored on the tab that protrudes from the bellhousing, and the cable case is attached to the arm. So the arm moves rearward and that pulls the center of the pressure plate away from the flywheel, disengaging the clutch.

The rest of the transmission internals are interchangeable between 69 and older, and 70-71 transmissions, and also 914 transmissions. The 70-71 transmission can be used all the way up to the 3.2 911 engine by using the 3.2 flywheel, and using the 70-71 clutch disk, pressure plate and throwout bearing.

I have a 70-71 911 transmission modified with 914 transmission parts connected to a 2.4S motor that I used in my 914-6 conversion. It eliminated the clutch cable pulley and removed the load on the clutch tube in the chassis completely. So no more broken clutch tube issues. It worked fine, but the durability was marginal with that amount of horsepower. I fixed it twice due to broken internals. That's the same reason Porsche went to the 915 in 72.

I hope that helps.

911parts · 12-21-2021, 04:38 PM

I believe the soft 70/71 pressure plate is hard to find so inevitably you'll use the later pressure plate for a 915 who's spring rate will break the factory plastic clevis. I sell an aluminium one

Mark Henry · 05:34 PM

Is there any reason to keep an old '70-71 aluminum (body and shoe) pressure plate?
The shoe has a laminate surface (chrome, steel?) that's starting to peel /flake off the aluminum shoe along the inside edge.
Does anyone rebuild these? Price of them you think someone would figure out a way.

I don't need one but it's a cool piece, very light. I've kept it because the ring gear has value and I've thought about machining the body for a lightweight 914 conversion clutch ring, that uses VW bus 228mm pressure plate.

gled49 · 12-25-2021, 07:00 AM

Scott’s Independent has modified pull type trans housings to push type by relocating the pivot bolt hole inward.

stownsen914 · 08:00 AM

Quote:

Originally Posted by Mark Henry

Is there any reason to keep an old '70-71 aluminum (body and shoe) pressure plate?
The shoe has a laminate surface (chrome, steel?) that's starting to peel /flake off the aluminum shoe along the inside edge.
Does anyone rebuild these? Price of them you think someone would figure out a way.

I looked into having one "metal sprayed" or plasma sprayed to bring it back to standard. Haven't gotten around to to it yet. I think the factory did some kind of heated bonding process with a copper friction surface or ferrous surface in different years bonded to the aluminum foot.

Those aluminum 70-71 pressure plates that also have the aluminum foot are impressively light. Like 5 lbs or something. Substantially lighter than the 915 aluminum sport plates we get today.

powderfinger911 · 12-26-2021, 08:44 AM

Quote:

Originally Posted by stownsen914

I looked into having one "metal sprayed" or plasma sprayed to bring it back to standard. Haven't gotten around to to it yet. I think the factory did some kind of heated bonding process with a copper friction surface or ferrous surface in different years bonded to the aluminum foot.

Those aluminum 70-71 pressure plates that also have the aluminum foot are impressively light. Like 5 lbs or something. Substantially lighter than the 915 aluminum sport plates we get today.

I had this done to my 69S pressure plate.