Homebrew Apex shift coupler
 

I realized I could make my own coupler from an Apex coupler after reading this thread, Stomski Shift Coupler a Winner

I bought these parts in anticipation of D-Day, (CLICK FOR A LARGER PIC)
http://jubjub.mine.nu/derPorsche/cou...arts_thumb.jpg

Here are the two couplers. Note how the stock coupler is shorter than the new one. I still have to add a shaft to the Apex coupler. I wish I'd paid attention to this difference.
http://jubjub.mine.nu/derPorsche/cou...ison_thumb.jpg

First step was making a new shaft. I decided to NOT cut the splined shaft off my stock coupler. Instead, I used a piece of smooth 5/8" chromoly rod.
http://jubjub.mine.nu/derPorsche/cou...grod_thumb.jpg

After cutting off a fair length (2-2.5"), leaving enough to grab hold, I had to machine the rod to match the O.D. of the stock splined shaft. I believe this diameter is around 0.580". The picture below is one setup I used. I had to reorient to get better results. This would have been easier with a lathe, but I don't have one. I ended up removing .045" instead of 0.040". I was a little gung ho and machined too much material.
http://jubjub.mine.nu/derPorsche/cou...ning_thumb.jpg

Here is the rough product:
http://jubjub.mine.nu/derPorsche/cou...left_thumb.jpg

Rod inside coupler:
http://jubjub.mine.nu/derPorsche/cou...pler_thumb.jpg

I then drilled the coupler to allow the set screw to grab the chromoly shaft. This is the installed shaft clamp.
http://jubjub.mine.nu/derPorsche/cou...shed_thumb.jpg

Next, I had to drill the other shaft clamp to install the cone-shaped set screw. That went alright, ignoring all the Taiwanese drill bits I ruined. The coupler is made of some tough steel or these drill bits are junk. :)

After I got it all together, I realized the coupler was too long. Arggggggg!!!! To make a long story short, I had to cut the coupler down about 3/8". I removed the shaft clamp and welded the chromoly rod to the coupler. The installed coupler:
http://jubjub.mine.nu/derPorsche/cou...shed_thumb.jpg
Notice how the side with the chromoly shaft is a lot shorter than originally planned. When the coupler is too long, you cannot engage 2nd, 4th, and reverse. This coupler is still longer than stock, but it works great with my Rennshifter. I originally complained about the lateral throw of the Rennshifter, but that was before I found I had a worn shift coupler.

I haven't driven the car with the new coupler. It felt OK during testing, but I was really impressed when I had it all bolted together and had the shift knob installed. I have a feeling this is going to be a great upgrade. When I consider my time and backyard engineering, $190 for the Stomski Coupler is a good price. However, I paid my dues. If you want help installing one on your car, let me know. I will trade my "expertise" in exchange for Porsche parts (oil filters, goodies, anything in my Pelican Parts Project list, or even a set of Recaro SRDs :)). I have about $95 invested in my homebrew coupler, and I can rest easy knowing it is the pinnacle of coupler design. ;)

Let me know if you want any more details.

Jurgen

Very cool project.

I made my own coupler as well.. I used a $35 universal joint instead of the apex coupler. With a lil bit of reseach and some fabricating skills you can save yourself a bit of money

http://forums.pelicanparts.com/uploa...ft coupler.jpg

Let us know how it drives!!

I just used 914 coupler bushings (on the advice of a buddy who races and builds 911 race cars). They have a round hole instead of an oval hole, so there is no slop. Super tight bushing fit. Combined with a factory short shift kit and all other new bushings, it feels very solid.

But, yours is very beautiful. Maybe a lexan access plate is in order!