Difference in cases, 901 transmissions?
 

I just bought a 902/1 5 speed Trany to replace the Mg case 4 speed in my car, is there any difference in the cases? I'dl like to take the guts out of the Al case and put it into the Mg case. I'd use the aluminum end plate so as to have a but more stiffness, but I am trying to be as lightweight as possible.

What is the S/N and Type # of your original transmission? My experience is that the magnesium case 4-speed 901/12 showed up about 1/3 into the ’69 model year. Not ’68. I’m not aware of magnesium case axle flanges that fit the SWB axles.

If you have a magnesium case 4-speed Type 901/12, it should have S/N 7091001 to 7091469. I would be VERY interested in the axle flange type.

To answer your question, you are far better off simply installing a ’67 902/1 in your ’68 911T (RoW). Both transmissions should have the 6-bolt Lobro CV joint flanges. The clutch actuation is the same. The 902/1 should not have the “simplified differential” and that is very desirable.

If you are intent on using a magnesium case, there are other possibilities.

If you want to install the internals from the 901/2 in your magnesium case, it is difficult and expensive. The ring and pinion needs to be reset and there is no guarantee of successful (quiet and long life) operation. The difference in weight is insignificant considering other factors.

Best,
Grady

S/N 2080054 , Model 901/1 (hard to tell)