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.

Axles and CV joints

<< Transaxle Install                        Mount Half Shafts  >>

Major System Category: Brakes & Suspension
Task: Assemble Half Shafts
Parts: Inner and Outer CV Boots
            Corvette CV Joints
            Porsche 930 CV Joints
            Porsche 930 CV flange
            Axle Grease
            Axle Half Shafts
Prerequisite Tasks:
Additional Costs:
Porsche 930 CV Joints $140
Porsche 930 CV flange $34
Lucas Oil Heavy Duty Grease (2 lbs) $14
Time Requirement: 3 hours
Date Started: November 22, 2014

Date Completed:  November 22, 2014

This task really doesn't have a prerequisite in the conventional manner. You can build these at any time. My approach was to wait for the transaxle to be mounted in the chassis. At this point, I am just waiting on getting the correct bolts to connect the 930 CV joints to the 991 Transaxle. This isn't a very difficult task, it is just messy. 

I used this end for the outer CV. This is the Corvette CV joint either from a parts pallet or donor car.

I used this end for the inner CV joint. You can see the groove for the retaining ring is closer to the edge.

The inner and outer CV boots come with grease and retaining rings. I don't think there is enough grease included, so I purchased the additional grease. The first thing you notice is that the ends of the half axle shaft are different and the manual is a bit vague as to which end is for the Corvette CV joint and the Porsche CV joint. I don't think it really matters. I have a digital copy of the manual, so I blew up the photo on the page and determined the end assembled for the inner CV boot.

This is the 930 flange and the inner cv boot. You will not get confused here. The inner boot is significantly smaller than the outer boot. 

The other difference betweent he inner and outer boots, is the inner boot fits inside the 930 flange, where the outer boot fits over the Corvette CV joint.

The other thing I found was that the inner boot is really tight when pushed onto the shaft. The outer boot is a bit loose. Before installing the inner boot, pop it into the 930 CV flange. It should be an easy fit. The flange will hold the lip of the inner boot against the 930 CV joint.

930 CV joint and inner boot attached to 930 Flange. 

The flange sits on the 930 CV joint. Granted installation to the transaxle will be a bit more challenging, because things will be horizontal and the whole is going to want to fall through the chassis and hit the floor. Just one of many joys in working on this car. I haven't decided whether I want to lean over the top  or raise the car tackle that install from the bottom.

Now for the messy part. The 930 CV joint is new, so it needs to be packed with grease. You want to make sure you avoid filling the center, because the axle needs to fit through there and it is just cleaner. Disposable plastic gloves are highly recommended. I also used a spreader to scoop and move the grease around. It is the same kind of spreader I have used on the fiber glass.

Porsche 930 CV joints packed with grease.

The Corvette CV joint repacked with grease. You can see the spreader to the left; I also clamped this in a vice to make it easier to work with. You just want to make this snug, because splines that attach to the C5 hubs is what I used to hold this steady.

Since I am still figuring out the CV bolt size for the 991 transaxle, I packed the 930 CV joints and sandwiched them between some cardboard. I thought the correct size for the bolts was M* x 1.25 x 50mm, because that's what Porsche used on the 997 transaxle. WRONG! My current theory is that I need M10 x 1.25 x 50mm. Once I fgure that part out, then I have to round up 12 of them.

Outer boot slips over the outside of the Corvette CV joint. Then you put a retaining ring on the boot.

One side finished, just repeat on the other side.

Transaxle Delivery

The Transaxle arrived today. It isn't just any transaxle. This one is a manual 7 speed, model 991. It is the same transaxle found  in the current production Porsche 911s. As far as I know, my GTM is the first one to sport this transaxle.

Shipping crate dropped on the Northern Man Cave floor.

This journey began March 2013. I am writing this in November 2013. I responded to a post of the Factory Five Forum (a place I have been too busy to visit over the past several months). A couple of phone calls later, we settled on a deal to purchase the 991 transaxle, plus clutch, pressure plate, fly wheel, mating collar and modification for inverted operation. Basically, this is an all in one deal designed to handle the 525 HP ls376/525 slated to end up mated to the 991.

This the normal configuration for the 991. In the GTM this is inverted. Note the blue drain plug and the shift markings.

Gbox LLC is a small shop in Boulder, Colorado. They deliver what they promise. The transaxle comes backed in a custom built shipping box. There is plenty of padding to keep things from banging on the way from Boulder to the Northern Man Cave. The top is screwed down. The best thing about this shipping arrangement is there is no shipping pallet to dispose of.

The 991 tilted on its side. The shift lever is in the middle of the transaxle. The black circle on the end is where the transaxle is bolted to the frame.

The current build site is very limited in space. Even though the engine will not be purchased for a while, it is necessary to get the transaxle into the chassis. My friends Matt and Gary came by to help me get the transaxle into the car. Normally, you take the body shell off the car to mount the transaxle. It turns out the opening under the engine bay in the chassis is big enough to slide the transaxle into the chassis. There is approximately 2.5 inches clearance. The lack of an engine is the only way this works. Again, I'll repeat the recommendation - put off the engine purchase as long as possible.

Mating collars for the 991 and an LS block. This is a custom piece. You can see the GBOX Logo at the top of the photo.

We positioned the 991 vertically with the bell housing flat on a plywood sheet on top of a dolly. We rolled the transaxle under the lift and eye balled the location to be approximately under the opening in the chassis. (B TW: Rolling the transaxle on a dolly is a lot easier than trying to find a grp on this beast and manhandling it anywhere.) We lowered the lift until it was just above the top of the 991. This means the bottom of the lift is a little more than 2 feet off the floor. Gary climbed up on the lift so he could give us a visual looking down through the hatch. I got on my knees so I could get a visual as the lift came down. Matt watched it from another angle.

Clutch already bolted to the pressure plate and fly wheel.

I brought the lift down really slow. We made a couple of minor adjustments (and we needed all sets of eyes on the transaxle to make sure we didn't do something bad). I got the bottom of the lift about 3 inches off the floor. This leaves the transaxle about halfway up to the cross member where it is cradled in the chassis.

Fly wheel. I so glad I just have to mount this in place.

Earlier, I measured the transaxle cross member and the opening on the transaxle bracket. It turns out the 991 needs an opening of 3.5 inches, and my bracket only has 2/75 inches. The transaxle bracket is the removable piece that can be swapped out between aither the Mendeola SDR or the Porsche G50 transaxles. The 991 is different enough that the bracket needs further modification. Last summer I jad the Vraptor pieces welded in place for the wing. I removed the bracket before the guys arrived to help. This made it easier, because this all comes down to brutal force to get it mounted.

These are the tabs that the transaxle needs to bolt through. They have to be cut out and moved so the inner diameter is at least 3.5 inches. When I dropped it off at Crystal Welding, I explained the situation and we agreed on the technical measurement of a smidge over 3.5 inches for the inner measurement.  

Now it gets tricky. The three of us looked down through the hatch at the transaxle. It is sitting there and it was kind of a Now-What moment. I clambered over the edge of the hatch and first stepped where the engine mounts reside. Matt leaned over the back end of the body shell, and Gary helped find things as we needed them. He thought about trying to heft it up. In the end, I tipped it backwards on the cradle. We had to be extra careful not to damage the drain plug. So I ended up standing on the dolly - this proved to be one of those dumb things that worked out okay.

I couldn't done this without these guys! Matt and Gary did a great job!

Matt held the back end of the transaxle, Gary had the 2x4 wood blocks and straps ready, and I tilted the 991 towards the cradle. Unfortunately, not only did the 991 move, but so did the dolly, the plywood sheet and my feet. I kind of did the Fred Flintstone run in place under the lift with a 200 lbs transaxle in my hands. Fortunately, we had enough leverage and the transaxle moved (relatively easily) into place. The dolly eventually slid out from under me and I was on stable ground. We strapped the and braced the transaxle in place, declared victory and congratulated each other on a job complete.

Here she is strapped and braced in place. I should have the transaxle bracket back in a couple of weeks, then she will be bolted into place until it comes time to install the engine.

Weld Wing Mount to Transaxle Bracket

<<  Mount Rear Suspension                                                 Transaxle Delivery >>
                                                                                               Racing Wing >>

Major System Category: Transmission
Task: Weld Wing Mount to Transaxle Bracket
Parts: Vraptor Wing Mount
Prerequisite Tasks: 
Additional Costs: $500 parts, $100 welding
Time Requirement: 1 Hour
Date Started: August 15, 2013
Date Completed: August 15, 2013
One of the optional items for the car is a functional wing. The wing advertised on the Factory Five site is the APR-300 67 inch wing made out of carbon fiber. The photos on the parts catalog page indicate the racing wing attaches  to the rear deck of the body shell. While the rear deck is reinforced by the transaxle bracket it is still fiberglass and it is not a direct connection to the frame. I a, mot sold on the idea that the fiber glass body shell can handle the stresses that are generated by a functional wing.

This is the universal wing mount kit from Vraptor. Four of the pieces are welded to the transaxle bracket. The other two pieces are bolted to the welded pieces and extend through the body shell to mount the APR wing.

This is where Vraptor Speedworks comes to play. They sell a universal wing mount that is welded to the transaxle bracket. A competent welding shop can weld these pieces for about $100 - in my case Crystal Welding. A wing mount that translates down force to the frame rather than the body shell. This thing is solid like a rock. This can handle whatever stresses I generated with a LS76/525 engine mated to a 7 speed transaxle on Nitti INVO tires. 

Top view of the modified transaxle bracket,

The transaxle bracket is secured to the chassis using four bolts. One of the things that concerned me was there going to be enough clearance when the transaxle is sitting in the cradle. Once the transaxle arrived, I discovered I had to further modify the transaxle bracket to handle the sleeve where trhe transaxle bolts to the bracket. I'm pretty sure there is no problem with the bolts. It turns out the Porsche 991 transaxle needs 3.5 inch sleeve, and the bracket I have only goes to 3.75 inches.

Bottom view of the modified transaxle bracket.

Transaxle Purchase

Early on in the planning stage I needed to make a decision between a Porsche G50 or a Mendeola SDR transaxle. Those were the choices. A great deal of discussion has taken place on the Factory Five Forums regarding these options. The G50 can be had in either 5 or 6 speed configurations. There are multiple gear ratio packages and kits to make sure transaxle runs inverted.

The Mendeola was plagued in the early days with delivery problems, but those seem to be old news. There are rumors of a 6 speed version. However, the production runs have been and will be limited runs. The SDR transaxle is a market opportunity as the G50 transaxles were scooped up for various build projects.

The transaxle doesn't exist in a vacuum  There are additional parts that need to be purchased:

• Flywheel
• Clutch release components
• Stage II Clutch
• Cable shift Assy
• Pump and cooler kit
• Bolt Kit
• Gear Reduction Starter 

The additional parts cost around $5000. I built the budget based on major systems for the car. The transaxle plus these parts represent the second largest cost for the build.

Transaxle cost works out as follows:

• A properly rebuilt G50 set up for inverted use costs around $9000.
• A new Mendeola SDR costs around $11,500.

I opted to go with a new Mendeola transaxle. My feeling was that there was less to go wrong with a new transaxle than a rebuilt one. I specified a Mendeola transaxle when I ordered the chassis from Factory Five.

Then I changed my mind.

Seven forward speeds. Two more than the SDR. One or two more than the G50. Factory new (and as of this writing) on a slow boat from Germany.

One of the benefits of not having all the money up front is that I can leverage changes in technology over the three years this is going to take to complete.

Early in 2013, Eric at Gbox posted a thread on the Factory Five forums asking if anyone was interested in a 7 speed 991 transaxle. The same transaxle that is in the new generation Porache 911.

My neck still smarts from the whiplash. Say what!?! Brand new, shipped from Germany, 7 speed Porsche transaxle!!!!

Good bye G50.

Good bye SDR.

Hello 991!

I am bouncing off the walls.

Gbox puts all the parts together and test beds it on an LS block before it leaves their shop for the Northern Man Cave. It is a brand new transaxle that is currently shipping in the 991 generation of the flagship Porsche 911s.

The bad news is this busts the budget. The 991 costs $13,500. Ouch!

Or does it?

One of the items high on the design list were paddle shifters. I contacted Master Shift (my vendor for the aftermarket paddle shift solution) and asked if they had done anything with a 991 transaxle. The answer was no. They had done a 7 speed pattern for a different transmission. I chewed on this for a  couple of weeks. I decided that I did not want to be the Mark I version for an aftermarket paddle shift solution. With great reluctance, I dropped the paddle shifter from the design plan and gained $3000 back to the budget.

The SDR option has the following costs:

• SDR - $11,500
• Additional Parts - $5000
• Paddle shifter = $3000
• Total cost is $19,500 plus shipping

The 991 option has the following costs:

• 991 - $13,500
• Additional Parts - $5000
• Total cost is $18,500 plus shipping

By dropping back to tradition bump shift and going with the 991. I am $1000 below the cost of a new SDR with paddle shift. This isn't funny money like what happens in Washington. This is my pocket book.

Originally, I had hoped to do the engine and transaxle in 2013. That is no longer going to happen. My concentration this year is the rest of the car and the transaxle.

As my wife's cousin said, "Someone is going to have some fun!"

I certainly am!