Transmissions – 911/01 into a 901 case

[Paul W]

Toying with a little project, building up a second 901 box for my 69 911 with taller ratios.

I have access to a donor 911/01 transmission (which has the ratios I want) and I was wondering if it’s possible to build the internals into a spare magnesium 69 case I have. I know many of the 911/901 transmission parts are interchangeable but is this swap possible?

Apologies in advance if this has been covered, didn't come up in any of my searches.
Thanks
Paul

[304065]

Paul I believe the 911 and 901 boxes are internally interchangeable-- subject of course to condition of parts and little things like the size of the threads on the shaft changing over the years, etc.

For a definitive answer you need Dr. Evil. Dr. Evil does not hang out at Pelican. Dr. Evil hangs out at 914world, you can find him here: 914World.com - The fastest growing online 914 community!

[Matt Monson]

A '69 mag case "901" is identical to a type 911 except for the clutch actuation. What you want to do is 100% doable. The parts could also be put into an older "proper" 901 aluminum case gearbox.

[djpateman]

Matt is the expert, so I cannot add much except for the advice to consider how you want to do the task. The ring and pinion are a matched set, and the gaskets between the intermediate plate and the main case set the pinion depth. The depth was determined at the factory and adjusted by the gasket pack. Provided you replace the pack with the same thickness you should not have to go through the process of adjustment again; it is tricky.
My method of exchange would be to slip all the parts off of the 911 pinion shaft, and on to the 901 pinion shaft, and then use the 911 mainshaft as it is. Now you probably will want to go through everything and use the best components, and fix any problems.

[Jon B]

Originally Posted by 304065

For a definitive answer you need Dr. Evil. Dr. Evil does not hang out at Pelican.

Yes, you should go elsewhere for a definitive answer about 911 transmissions, you won't get anything definitive here.

The 911/01 internals are a direct fit into a mag '69 901 transmission case, but don't expect case dimensions to be identical, you should check the ring & pinion, diff bearing preloads and adjust as necessary.

[Paul W]

Thanks for the detailed answers.

Given the box is going to have to take the torque from a 3.2 (Webers / SSI) I would probably go as far as an aluminium intermediate plate and side cover anyway, which leads me to wonder whether the plate in the 911 could be used as well?

Using this as an opportunity to teach myself about the workings of a 901 transaxle though I'm happy to outsource specialist tasks to a mechanic.

Cheers