901 gear decoder & interchangeability of gears

[chris steineger]

I have several 901 gear boxes:

(2) 901/ five speeds for 911
- first one has blown pinion bearing;
- second one is good but worn 1st gear dog teeth
(1) 902 five speed for 912 - great condition inside

I'm trying to build 2 good trans from all the parts

Does anyone have a chart which decodes the gears ?

Thanks for any help,
Chris

[Walt Fricke]

Go the Porsche North America website. You can download the parts manuals for the years in question. Unlike parts books these days, the old ones give the tooth counts for each gear.

My guess is that all 901/902s have interchangeable gears, as well as some if not all other parts. But you'll need to hear from a guy with 901 experience - I'm a 915 guy.

[Trackrash]

Walt, won't this work. Sorry for the hijack.

[oldie44]

All the 901 and 902 transmission gears are interchangeable. 914 and 911 (1970-71) gears fit also.

[Bill Verburg]

Originally Posted by chris steineger

I have several 901 gear boxes:

(2) 901/ five speeds for 911
- first one has blown pinion bearing;
- second one is good but worn 1st gear dog teeth
(1) 902 five speed for 912 - great condition inside

I'm trying to build 2 good trans from all the parts

Does anyone have a chart which decodes the gears ?

Thanks for any help,
Chris

[Matt Monson]

Thanks Warren...

901/13 gear question

[hagopian04]

Do the 901 gears interchange with 915 gears (ie. fit either box)?

[djpateman]

No, the 915 shaft centers are farther apart than the 901 shafts.
In general here I am speaking of a 5 speed 901/902/911/914 box; a 4 speed essentially has first gear removed in the physical sense. A normal 5 speed has a fixed second gear on the mainshaft; the 4 speed has a fixed first gear; a 904 mainshaft is required to allow second gear to be changed.
Note that third gear sets are reverse of the 4/5 sets. If you use them in the "wrong" location the ratio will be reversed. Some gear sets are available in both types; example an O third and an O 4/5 set.
The 915 box is an entirely different design.