901 vs 911 transmissions

[dotorg]

Whats the difference with these?

I assume a 911 series will not cleanly bolt up to a SWB car with (presumably) a 901?

My L is a sporto conversion, I've been thinking of picking up a spare transmission and wondered if 911's are largely out of the question.

[Grady Clay]

The 901 is ’65–’69 aluminum casting and the 911 is ’70-’71 only magnesium casting.

The advantages of a 911 over a 901 are the easy use of the 225 mm pull-type clutch, slightly lighter weight for the same internals, and accept the 915 and later LSD. It uses the M10 4-bolt 108 mm big CV joints. They also have slightly wider 2nd and 3rd gears. It is a bolt-in exchange for a 901 with the addition of clutch cable and assorted parts and adapting the axles.

The disadvantages are it is probably difficult to find one in good (repairable) condition and the magnesium casting is more flexible and susceptible to corrosion.

For installation in a ’69 there isn’t any issue with the axles – it is a bolt-in. Installing in a ’68 and earlier requires some inventive adaptation. The easiest is to make adaptors and continue to use the smaller (and shorter) ’66-’68 Lobro CV. I wonder if the 100 mm transmission CV axle flange from an ’84 and earlier 915 would be the correct part to adapt to the smaller early axle? 923 possibly?

I don’t think it is feasible to use the 108 mm CV without changing to the ’69 and later trailing arms. A BIG $$$ deal.

I have one of these set up for my SWB 911 – 915 LSD, 904 shaft, 215 or 225 mm clutch, pull or push, and 100 mm CVs.

Best,
Grady

[dotorg]

Ow, that hurt my brain. That probably means I should just assume the answer to "can I use the 911" should be no, even if its not really.

If I'm following you, the axles would need to change or use an adapter, as the bolt pattern for the 901 and 911 aren't the same, and something about the clutch mechanism is different? Does that mean the clutch on the 901 wouldn't work with the 911?

Talk slowly and pretend I'm five here...

[silverc4s]

dotorg,
As one with some experience in the specifics you are asking about, I can tell you this much:
Based on my changeovers done, and for all of the reasons that Grady covers well above, the 911 is NOT a suitable spare for a 901. Too many differences.
You could make either one work in your chassis, and the 911 clutch is more available (i think) and stronger, but if you are already converted to a 901, you will need a spare 901, or 902 4 speed would be an easier modification into a spare, IMHO.
Good luck, I think these transaxles are getting hard to find in any reasonable condition now..

[Plavan]

I bought a 914 case, and found all the parts like Grady said (Where were you earlier Grady ). I did this on the race car so I could install a Guard LSD. It works great. I just needed some 70 stub axels, 70 nosecone, and a 1969 side cover for the clutch cable. I also added a billet aluminum intermediate plate for strength. It works flawlessly. Bolted right up

[jluetjen]

Dotorg;
As a spare, I'd have to say that a 911 box just doesn't seem to be worth the trouble. I don't think that the 901's are that rare and if my memory is correct, they were done both in aluminum (4sp 901/06 and 5 sp 901/07, '66-'68) and magnesium (4 sp 901/12 and 5 sp 901/13 in 1969). Using a 914 box and swapping the diff to the other side may also work since the 914's all used the same clutch style as the 901's (I would confirm this first though!).

There's still the details of the flanges and correct stretch-bolts to hold them in.

[randywebb]

This might be useful if you are hunting and need to ID some transmissions. I definitely agree with the consensus to just find another 901 for your car.

[jluetjen]

Randy;
Let me guess -- from Left to right:

G50?
915
911
901 (Aluminum)

Right?

[randywebb]

yup - sorry thought it was obvious.