Cable Shifter

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Major System Category: Transmission
Task: Mount Cable Shifter
Parts: 991 Cable Shifter
Prerequisite Tasks:
Additional Costs: Part of the transaxle purchase
Time Requirement: 8+ hours
Date Started: January 26, 2015
Date Completed: January 30, 2015

The 991 transaxle is the 7 speed I purchased from GBox. It came with the cable shifter. The GTM is designed for the much older G50 transaxle and a cable shifter that is housed in a square metal box. If you go with a rebuilt G50, then you won't have much of a problem, because everything will fit.

Porsche 991 cable shifter and Vraptor shifter mount.

The G50 transaxle first went into a production 911 in 1987. I was much taller, thinner and younger in those days. Sometime between then and now, Porsche quit producing square cable shifter housings and switched to curved polymer housings. Guess what, those don't work very well with the GTM bracket welded to the frame where the cable shifter bolts on horizontally.

Vraptor  cable shifter mount. The smaller piece (top) bolts to the frame. The larger piece is designed to attach to the rear of the cable shifter and it bolts tot he smaller piece. 

The current list of changes caused by going with a non standard transaxle are as follows:

1. Redesign, cut and weld the transaxle bracket to accommodate the wider 991.
2. Build a cradle to hold the inverted 991, and deal with fitment of the drain plug.
3. Order new half shafts for the CV joints.
4. Order special bolts from Porsche to attach the 930 CV to the transaxle. You need 12 of these and Porsche charges $4.50 per bolt. Trust me, you can't find these bolts anywhere else.
5. Purchase an extra set of cables and perform magic to connect them. Jim at cableshift.com was a big help!
6. Fabricate a mounting bracket for the cable shifter. I purchased the Vraptor Speedworks cable shifter mount. This proved to be a good starting point.
7. Finally, (I hope), a 7 speed shifter knob (in the correct pattern) and boot. I got this at Gaudin Porsche Parts in Las Vegas. Mark helped me with this purchase.

Porsche 991 cable shifter and top part of the Vraptor bracket. I'm just trying to get an idea of how this is all supposed to work.

The GTM design envisions bolting the cable shifter to the side bracket in the upper tunnel. The 991 cable shifter envisions four or five bolts into some kind of flat plate for a vertical mount. And did I mention, it is a round polymer shape.

I ended up enlarging the opening for the cable connectors. This was pretty easy using cut off wheel on the die grinder.

I figured out I use the Vraptor mounting bracket as a staring point. This is a two piece bracket that bolts a smaller piece to the frame and establishes an angle. The larger piece bolts to the cable shift box and then to the smaller piece. 

This is the bracket looking straight down. The cable shifter bolts into the rails. Ignore the four holes. They all had to be moved towards the passenger side (bottom) because I failed to account for the square piece inside the frame that is supposed to be used to bolt the G50 cable shifter to the frame. 

I had some angle aluminum stock. This may not sound very exotic, but I have discovered that you can fabricate a number of useful things for the car using this stuff. Since most of it will be hidden, it doesn't have to be a perfect job - just functional. I designed the bracket so I could bolt the cable shifter vertically into the angle stock. There are four 1/4 inch holes.

I trimmed these two parts off the cable shifter. They were just plastic.

The 991 cable shifter had an index tab and an additional hole. I had to cut these off the shifter, because they were not going to work for me. I used to get nervous about things like this, but now I just think it through and keep working.

Vraptor lower mount bolted into the frame.

I bolted the bottom piece of the Vraptor mount to the car, then clamped the larger piece to that one. This allowed me to work with the bracket and determine where metal needed to be trimmed so I could accommodate the frame.

I had to remove some material to accommodate the driver's side of the frame. After a fair amount of mumbling, wandering between the car and bench and maybe a harsh word or two. I had something that worked.

The front side of the bracket needed to be secured to the inside top rails of the tunnel. For this I used a heavy, straight aluminum bar. I bolted this to the front of the bracket, then cut 2 three inch pieces of angle stock so i could bolt one end to the bar stock and rivet the other end into the top frame of the tunnel.

Frot bracket. It is attached with rivets to the inside of the top tunnel frame.

I reinforced the area where I bolted the shifter to the bracket with 2 six inch steel strips. I wanted this piece to be as solid as the Wing mount on the back end of the car. I put everything together, then crawled into the car and got the masterpiece bolted in place.

Finished product sitting on the bench.

Finished product installed in the car.