901/911/914 Tranny parts sharing questions.

[joeblow]

Being an early LWB guy my questions really center around what is available to keep my car going.

I have a 901 now, used to have a 911 and am toying with building up a spare. Obviously 914 boxes are plentiful.

What I am assuming is that the 914 boxes can be converted to 901/911 by using the 901/911 nose cones and flipping the R&P? Is this a correct assumption? I know the gear sets are compatible.

Obviously clutch components are vastly different and having gone through the 901/911 clutch swap I know that the clutch fork pivot location will likely also be different depending on the type of gearbox.

Thanks in advance for the input Gentlemen.

[Grady Clay]

Joe,

I’m probably not going to tell you anything you don’t already know with your trials over the years.
You successes in the face of various disasters is an inspiration.

At some point you will want to decide if you want to go back to a type 911 with a pull-type clutch or continue with the 901 and the push-type clutch. There are ± to each.

I recommend you collect a good late (rectangular S/N boss) 1971 main casting, a good intermediate plate and nose piece and a hard-to-find original good side cover. These will be increasingly difficult to find. Murphy says you won’t find them at acceptable price if you need one.

Among the three transmissions (901, 911 & 914), the differences are in the castings and the shift linkage for the 914s.

The big difference is between the 901 & 911 (same as 914-6) and the 914-4 in the quality of the gear manufacturing. The 914 gears were manufactured with cost at the forefront. Yes, 914-4 gears and other parts are directly interchangeable. You will note that there are no manufacturer’s mark, dates, or matching-pair numbers on 914-4 gears. Some have a ‘VW’ stamp or cast mark.

It is said that 914-4 gears are noisier than 901/911 gears. I have no direct experience.

Yes, you can convert a 914 transmission for use in a 911. There are other threads on this conversion.

Given the choice and time, search out ’68 through ‘71 good-used or core 901 and 911 transmissions.

Some of the more important changes are the introduction of the ‘reinforced’ input shaft in 1968. The 1st & 2nd gears are slightly wider (by 0.6 & 0.8 mm) starting in ’70. The differential is massively increased in strength (interchangeable with 930) in 1970. You should research the 'simplified' differential issue and the update. The 'dam seal' mod is aplicable.


Eventually, you will find the only good choice will be to build your own ‘new’ transmission from good-used original parts and a few new bearings, gaskets and seals. It is worth the effort to start a ‘stash’ now.

Best,
Grady

[Tom F2]

Grady,

What is different about the late main housing with the square boss for the numbers?

Hasn't anyone figured out a fix for the worn side covers, short of a billet side cover but better than a pair of tie wraps or a klugey piece of bent iron?

[Grady Clay]

Tom,

There are a number of subtle reinforcements to the casting with the rectangular boss.
While these are apparent when you have castings next to each other, there are probably more.
This casting was used for less than one model year (’71).
My theory is Porsche would not have made this significant investment without good reason (..but you never know. With the 915 they went to the input shaft seal installed from the inside and moved the numbers to the lowest point on the tranmission where they were sure to be scraped off. )


In the early ‘70s, another supplier with PP initials made a little aluminum piece to replace the worn ring on the differential side cover.
You milled (sawed?) the old ring off.
This part bolted in place with two M5 screws from the inside.
The screws were supplied, drilled for safety wire and had soft copper sealing washers.
We added epoxy between the alu and mag.
This should be able to be made with CAD-CAM easily and inexpensively.
I haven’t seen one available since the late '70s.

Best,
Grady