915 shift housing on a 901 transmission: SUCCESS

[pope]

Wow! What fun!

A 901 shifter is not easy. You do get used to it after a couple of thousand miles and can, more often than not, shift relatively quickly (except 1st to 2nd ). But the sloppiness and the tremendous throw are what annoyed me in this car. You drive this nice compact, tight and swift car, and the lever feels like jelly..

So I decided to go for the short shift kit. Along the way, I found that the SSK is not made for a 901 housing, meaning you need to upgrade to a 915. Then I found that the 915 housing is not made for the 901 shift pattern (dog leg). So, here's how to solve this.


The easy part is that you don't need to take apart your shifter while you prepare the new one since everything is new: you do not reuse anything from the 901 shifter except the knob (and the crush sleeve inside if you can save it).


Here's what you'll need:
0. If you’re a very early 911, your shift linkage may not be up to this task. I’m not sure about this so you will need to do some research. My 1970 was fine.
1. 1 x 915 shift housing: 91142401906
2. 1 x Short shift kit. I got the factory (M241) but I guess the others are very similar.
3. 1 x Seine systems gate shift kit (for 901).
4. 1 x crush sleeve for shift knob 99953200300
5. 1 x 915 shift lever boot: 91142418101
6. 1 x 915 shift housing tensioning sleeve (backside pin): 90019703501
7. 1 x 915 shift housing threaded pin (forward pin): 91142433500
8. 2 x 915 shift housing pivot pin locks (c-clamps): 99916602702
9. 1 x tightening nut for 91142433500 and spring washer. This is an unusual M14 with a 1.5mm thread I think as I haven't managed to find it yet.
10. 2 x spacer washer for the 2 pins (fore and aft) between the housing and the housing fork.
11. Any parts you choose to change based on the shifting improvements tech article. Shift ball bushing, forward bushing for shift linkage, shift coupler bushings (or change the whole shift coupler), 2 conical screws.
Items 5-10 are not mentioned as required parts in any of the documentation I read, so if you’re putting a SSK on your 901, make sure you get them.

The procedure I followed is:
1. Put together the new housing following Seine instruction manual that comes with the kit. The parts you’ll use for this are 1-3 and 6-10. The instructions are very straightforward and easy to implement.
2. Make on the bench adjustments to the shifter as per instructions.
3. Took out shift coupler from the car to change its bushings and conical screw. Had a bit of a hard time here. The Coupler whisperer thread is great for this task.
4. Pulled old shifter with housing and replaced other bushings and conical screw.
5. Installed new shifter.
6. Enlarged hole in carpet, installed boot and knob.

The most difficult part of this procedure is adjusting the coupler. I found that a very small adjustment will make a big difference in how the shifting works. So don’t get disappointed but keep trying. Test the extremes to see which adjustment does what. Have a look at this thread too: 901 tranny shifter adjustment
Be sure that your shift linkage does not have slop in it. I had not tightened the conical screw on the coupler enough and the first day of adjustments was wasted. There was no way I could get all 3 planes to work correctly. Make sure you tighten both conical screws (mine came with some loctite on them or something and I mistakenly thought I had screwed them in all the way).
The other documentation I used for this:
Installing the 911 Factory Short Shift Kit
Shifting Improvements #1
901 Gate shift kit - Seine systems
Shifting Improvements #2




In conclusion, I’m very happy with this modification. If you like originality, don’t do it. There’s a big difference in the feel: I guess it feels more like an 80’s Porsche rather than a 60’s . On the other hand, it is much more fun to drive. The shifting is not quicker as such but much much more accurate and the throw is now reasonable: I don’t have to bend over to reach 4th.

If anyone would like to correct anything or add, please do. I am far from being an expert.