Diffuser

<<   Mount Half Shafts                                                  >>

Major System Category: Body (Undercarriage)
Task: Diffuser
Parts:
Vent Louvers
Strakes
Diffuser Grille
Diffuser
Prerequisite Tasks:
Additional Costs: $250 (estimate)
Time Requirement: 8+ hours
Date Started: February 20, 2015

Date Completed: February 28, 2015

The diffuser is the unwieldy carbon fiber piece that fits under the transaxle and extends slightly past the lip of the rear end. Factory Five supllies these little posts (ugly as sin) to connect the top of the Diffuser to the bottom of the rear frame (just below the license plate and the exhaust pipe openings). Each is entitled to their opinions, but these little post that hold the diffuser in place look cheap.

The Diffuser grille comes flat. The tabs need to be bent to provide attachment points for the grill to the body shell. These are no 90 degree angles. In order for the grille to fit properly, the angle is more acute (i.e. less than 90). With all the pieces already in the area (e.g. transaxle bracket, chassis mount for wing, backup camera, lights) there isn't a lot of room to get a rivet tool in there. I went with  short bolts and locking nuts.

Fortunately, Vraptor Speedworks makes this marvelous looking diffuser grille. I think this is a necessary purchase (from an aesthetics perspective) that really makes the back end look finished. The shape of the Gen I and Gen II cars is different, so this grille only works for the Gen II cars. I have decided to bolt the diffuser grille and diffuser to the car. The manual says to rivet everything in place. I prefer to have a way to access everything on the car without having to drill out 40 rivets.

I painted the diffuser grille gloss black, bent the tabs using a small vice as my metal bending tool. This is the grille clamped in place for initial fitment. I discovered that I had to "bow" it a little to get to go flush on the edges. The oither issue I have with rivets has to do with maintenance access. If you go the rivet route, then the only way you will ever get it off the car is to drill everything out.

Before I could pre fit the diffuser, I had to get the  half shafts and the transaxle installed. This way, I could remove the jack stands from  under the rear chassis and have free access under the car for the diffuser.The manual indicated that you should measure 1.5 inches from the rear edge of the diffuser. This is how far the lip of the diffuser extends beyond the rear fiberglass shell. This is probably going vary by .25 inches from car to car based on how well everything matches up for the fit between the diffuser and the edges of the body shell.

I used painter's tape to lay down a strip then I marked off 1.5 inches along the rear edge with a Sharpie. The blue tape is where I masked off the opening for the transaxle housing..

There are three places I ended up having to cut the diffuser for the initial fit. There is a section of the transaxle housing that extend below the line of the diffuser. This seems pretty common for most GTM builds that I have examined. Certainly, the 991 transaxle continues to provide its share of challenges. The other place I ran into issues was the bell housing. The lip interfers with the forward diffuser edge.

This is the diffuser and the grill clamped into place to see how close I was getting on having the transaxle opening correct. This seems like the measurement should be straight forward, but it isn't (at least for me). The problem is the diffuser piece is somewhat unwieldy (I came close to dropping it more than once) and the transaxle housing is a combination of curved shapes and straight lines. In addition, you need to worry about the side ot side fitment between the diffuser and the bottom of the body shell. You can see the cardboard roller I used to assist me in getting diffuser on and off the lift.

I measured about a gazillion times and made a 6 inch square cut for the transaxle housing. I used a Rockwell VersaCut for the initial opening. I used a die grinder to make the cuts on the leading edge to clear the bell housing. To handle smoothing out the edges, I used a router table and a plunge router to smooth out the edges for the cuts for the opening. I set up the fence on the router table to handle the straight cuts for the bell housing. The other cuts I made was to widen the areas around the control arms for the suspension.

Finally satisfied with the cuts for the transaxle, I did a preliminary lay out for the louver vents. This is before any drilling, painting or bending. There is a very definite right and left side to these pieces.

All of this took several iterations between cuts and remounting the diffuser on the car. The lift proved its worth once again. I had the car about 5.5 feet high. I had a roller behind the rear wheels. This allowed me to slide the diffuser into place and to check the fitment.

These are the cuts for the vents. You need to be very precise here, because you have to be  aware of the edge beyond the body shell and running our of room as the diffuser bends around the frame. There is maybe a .25 inch fudge factor. I used the VersaCut, for the gross opening, a drill for the rounded corners and the router table to smooth and straighten everything out.

Once satisfied with the cuts for these openings, I started on the louver vents and strakes. The louvers are shipped flat. I used these as a template to determine the minimum cut opening for the louvers. I used the same method for the cuts and drilled out the corners to better provide for rounding. Next, I used the drill press to make the holes for black rivets. I purchased these a long time ago, because I think it looks really cheap to have this beautiful diffuser peppered with shiny aluminum rivets.

These are the strake and vents. Vraptor did a good design job here, because the strakes rivet to the outside and the louvers rivet to the inside. I was able to use a single rivet to fasten the louver vents, diffuser and strakes together. These are the black head rivets.

The strakes are designed to be attached with the same rivet. I used the louvers as a template for those rivet holes. The diffuser piece is easily drilled with a hand held tool. Before final assembly, I painted all parts a gloss black and opened the louver vents, by bending them open. This is really pretty easy to do, you just need to take your time.

The end result is the diffuser with plenty of venting. This is clamped in place. I will not worry about final attachment until the car is painted. I plan to go with  1/4 - 20 Helicoils for the frame and bolts and lock nuts for the body shell to diffuer connection. Some of those fasteners will be awkward, but I have a way into the underside of the car should the need arise.

Mount Half Shafts

<< Axle and CV Joints                                         Diffuser  >>

Major System Category: Transmission
Task: Install half shafts between rear hubs and transaxle
Parts:
New Half Shafts (Custom Made)
Prerequisite Tasks:
Additional Costs: $1300
Time Requirement: 8+ hours
Date Started: November 15, 2014

Date Completed: February 14, 2015

The governing principles for Super Car Build are quite simple:

• Failure is not an Option - Unknown
• Never, never, never give up. - Winston Churchill

I decided that to do this job right it might take longer than I wished, and probably cost more than I anticipated. Okay. I refuse to end up as one of those guys with a half built car and a $50,000 price tag for failure.

This is an assembled half shaft per the Factory Five Manual. Looks good and it certainly would fit a G50 transaxle. But I have been off the reservation  since I went with the 991 transaxle. 

The half shafts should be a simple task. Some grunting, scraped knuckles, a few choice words, but nothing that should take months to complete. In my post on the Cable Shifter, I listed all the things up to that point that had to be adjusted for going with a Porsche 991 transaxle versus a Porsche G50. It is a long expensive list, but the end result is a state of the art, 7 speed transaxle straight from Germany. The kind of transaxle a super car deserves.

The green circles show the shaft stubs on the 991 transaxle. They measure out around 22 inches. I know you're supposed to get this stuff down to the 1/4 inch. However, there is enough play that you have some room to work with.

I assembled the half shafts with the Corvette CV joint on one end and the 930 CV on the other end. It took a little time, but it was a straight forward task. The next day, I planned to install them. I slid the Corvette CV into the Corvette hub and tried to get the other end of half shaft to connect to the transaxle. Guess what, when the shaft is several inches too long, it just isn't going to happen. The problem arises that the width of the G50 between the shaft stubs is 10 inches. The width of the 991 is 22 inches. At the time, I didn't know what the width of G50 was. I know now it is 10 inches.

This is the half axle from the Drive Shaft Shop. No, it isn't made out of gold. My buddy Brian commented that it was a beautiful unit. It is - these guys do good work.

I sent an email to Factory Five support and asked them for that dimension. They didn't know the answer. Then I asked them for assistance in specing out new half shafts. They buy their shafts overseas and couldn't help either. What about the spline count. They thought it was 28. Ever count splines by hand - you might go cross-eyed. The only thing they said was figure out the difference and divide by 2. Duh, I ALREADY KNEW THAT!

I ended up taking off the caliper, rotors, tie rod and shock absorber to get a enough room to work. My buddy Charlie chided me that I was supposed to be putting things together. In this photo, I was doing the heat - tap - heat  -tap process to get the CV splines through the hub.

If Shane (Vraptor SpeedWorks) had had a G50 sitting on the floor of his shop, he would have measured it for me. I ended up getting the dimensions from GBox. Trust me, wherever they have the dimensions posted on the web is well hidden. There are diagrams, but they are so distorted that you can't read any numbers off of them.

This bolt is the correct size and that is the Torx head I needed to install it.

I don't know what caused me to check, but I decided to see if the bolts fit. Of course not. Porsche in their modern transaxles have switched to a M10 x 1.0 mm thread. These are about as common as the proverbial unicorn at the end of the rainbow. I tried finding these on my own, and finally called Carousel Porsche Audi in Golden Valley, MN (where I had the Boxster serviced). They ordered me 12 bolts designed for the 991 transaxle. And I thought I was home free, I was just getting in line for another smack across the head.

My weapon of choice (eh, I mean tool) to get this monster assembled.

The assembled half shaft with CV joints on both ends is smidgen over 30 inches long. The actual shaft if 23 inches long. This means I needed a half shaft that was 17 inches long before I added the CV joints. I probably double checked this measurement 100 times. I knew this was not going to be cheap. I ended up ordering custom half shafts from the Drive Shaft Shop. It is a good thing they knew their business, because I certainly was swimming in the deep water. He told me how much it was going to cost. I swallowed hard and gave him my VISA info. They were on the door step in two days. These guys do really good work.

This is a beautiful sight. Normally, it takes about 20 minutes to get here. I had a minor 4 month detour.

So now I have the bolts and the half shafts. Everything should work - right? The first problem I run into is that the splines on the Corvette CV joint are new (versus the ones I got from Fparts on the donor pallet - that seems like a million years ago). The spline is correct, but these buggers are really, really tight. There is a new hardware store 3 miles down the road from the NSMC. The dog and I ended making two trips that day. The first one was to buy a torch.

Installed! I was on top of the world, and greatly relieved that it finally worked.

I used the torch to heat up the hub and heat up the end of the Corvette CV that goes through the hub. It took about 15 - 20 minutes on each side to heat, tap lightly with a hammer, heat - tap -heat - tap. The Corvette CV joints that came with the donor pallet use a 34mm nut. I had purchased a 34 mm socket. The nut required for the new CV uses a 36 mm socket. No, I didn't have one of those behemoths handy. This precipitated trip #2 to the hardware store. The pup was beginning to think I was insane.

Bracket installed on the chassis to reinforce the area that I had to remove material from.

Back at the NSMC, I believe I see light at the end of the tunnel, or it could be an in bound train. It was a train. I get lift to the proper height, I position CV and I can't get there from here. The problem  is the cradle I built for the transaxle to keep the drain plug safe. I did this, because I didn't want to cut into the chassis. <Sigh>. The only way to make this work is to cut into the chassis. Out comes the cutting wheel and angle die grinder.

Another look at the channel brace I built.

A long time ago, my dad was faced with a similar problem. A building inspector decided that two 7 inch logs was not sufficient to support a structural truss. This was a bunch of hooey, but dad was also driven to get this house built. A few days later he showed up with channel braces that distributed the load else where. I adopted this idea, and created a sleeve to reinforce the area where I cut away material. My dad was a brilliant engineer. I'm just a kid using his idea. I built the sleeve and removed the cradle. Now the everything should fit - right? Nope.

Those bolts that I special ordered from Porsche -  they were short. However, I had one thing that I never had when I looked for those bolts on my own - a Porsche part number. I maintain an office at the NSMC. So I sat down and brought up Pelican Parts. I found the bolts for the 991 transaxle (M10 x 1.0 x 46mm). I also saw in the related listing transaxle bolts for 997 transaxles. A different part number. I clicked on that link and discovered that Porsche changed the bolts when they went to the 991 transaxle. The older bolts are M10 x 1.0 x 50mm. Well what did I have to lose, I ordered 12 bolts. (I have  acquired several sets of bolts that do not work in this application.) I was already a gazillion bucks over budget on this task, what's another $20. My dad was driven to build a house; I'm driven to build a car.

The new bolts arrived. I tested them in the transaxle and they were the correct thread and pitch. They were long enough going through 930 CV. I hooked up the air ratchet and attached the biggest Torx bit I have. Literally, 20 minutes later I had everything attached!

"Never, never, never give up!"

Cable Shifter

<<                                                             >>

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.

Cockpit Rear Window Construct

<< Body Shell Prep                           >>

Major System Category: Body (Shell)
Task: Finalize rear cockpit window
Parts:
Prerequisite Tasks:
Additional Costs: Set Belt restraint bar  $200
Time Requirement: 2 hour
Date Started: November 1, 2014

Date Completed:  January 11, 2015
I needed a break from the wiring problems, so I started working on parts of the car that I could finish and put aside. The rear cockpit window is such a part. One design change I made was to go with a racing 4 point restraint system rather than the Corvette 3 point system salvaged from the donor vehicle. To make that work I needed a restraint bar.

The seatbelt restraint bar.

This is a hefty piece of gear with attachment points welded for easy bolt on to the chassis.

Painted black.

I purchased a restraint bar from one of the other GTM builders on the Factory Five Forum. The restraint bar bolts through the rear cockpit window frame and directly into the chassis. It is a great design. I started on this on my final 2014 trip down south to the new build site. The build manual calls for the application of a cloth covering. I decided to just paint the frame and the restraint bar black. I had a small paint booth already established and proceeded to the paint the parts

Rear cockpit frame. I would suggest mounting this in the car, before working with it so you understand the orientation.

Painted black.

On mt next trip down, I moved all the glass to the new build site. This included the cockpit rear glass. Some people have replaced this with clear Lexan, I decided to stick with the glass. The hardest part of the installing the gasket is in the half circles on either side of the frame. I started the gasket on the straight portion of the frame and worked my way around.

Gasket tool provided with the Factory Five kit. Use it. It makes the job easier.

Gasket installed.

Factory Five provides a gasket tool. It works to a point. The trick here is to get as much of the window into the gasket as possible. I tapped the edge of the cockpit frame on the floor to drive the window further into the gasket. This got it far enough into the gasket so it seats into the gasket. A friend suggested you could uses soap to ease it into place. The gasket tool comes in handy to pull the lip of the gasket over the edge of the window. 

Rear frame, window and restraint bar. Obviously, the blue tape is there for protection. It will be removed on final assembly.

Everything bolted together.

Racing Wing (optional component)

<< Weld Wing Mount to Transaxle Bracket                          >>

Major System Category: Brakes & Suspension
Task: Mount Racing WIng
Parts: Wing Mounts
             Racing Wing
Prerequisite Tasks:
Weld Wing Mount to Transaxle Bracket
Additional Costs:
Vraptor Speedworks Universal Wing Mount $489
APR GTC-300 Carbon Fiber Wing $1350
Time Requirement: 4 hours
Date Started: January 6, 2015

Date Completed:  January 8, 2015
I told my long time sparring buddy that I was getting ready to cut into the back end of the car. He expressed concern. I explained that after this much time on the car, very little frightens me anymore. Besides fiber glass can be fixed.

The wing arrives in a long box and wrapped in bubble wrap.

To give a sense of scale, the rolling bench is 48 inches long. The wing is 67 inches.

 All parts are purchased from Vraptor Speedworks (Shane does a great job). The Vraptor wing is the same one offered through the Factory Five website. The main difference is the attachment points are custom to the Vraptor mounting system. This is a very solid piece of gear. The back end is greatly reinforced by this addition.

The initial cut. I originally figured it would be 7 1/2 inches long. I needed 8 inches to make everything work.

I added rear body shell louvers to the build. I masked off the area, and came up with a rough measurement of 2 7/8 inches from the edge of rear louver opening. The mount comes in three parts that are bolted tot he welded transaxle bracket, then bolted side ways through slots for the portion that pokes through the rear body shell, and finally the third piece that rests above the body shell. All that to say I was inside of a 1/4 inch and well within tolerances for the mount adjustments.

The cut needs to be this wide to work. I already have a solution for cleaning up the edges.

I used a angle grinder to make the initial cuts. Once those were wide enough, I used a rigid sanding wheel on a die grinder to shape, smooth and widen the cut. I strongly recommend wearing a breathing mask and face shield. There is a great deal of dust released when cutting into the back end like this.

This is the middle part of the bracket poking through the hole. This is secured to the bottom bracket by three bolts.

The cut ended up being 8 inches long. I ended up about 1/2 inch off the rear of the car, and I had to trim some material around the exhaust vent openings. Keep the socket wrench and hammer handy, because I had to loosen the bottom of the bracket and tap it back and forth to line things up.

This shows the middle and top part of the mount bolted together and the length of the cut.

The second cut went much faster (probably, because I had some idea of what I was doing).This was on the passenger side, and this is where I need to move it over a tad. I don't think the difference will be noticeable.

Driver's side mount installed. Once I got to this point, I knew I'd get to the end of this task tonight.

Once I had the middle and bottom brackets bolted together, it gets very easy. The one thing I ran into was the bolt closest to the rear of the car is snug. Not uncomfortably snug, but I had to use hand tools and not my power tools to tighten it up.

Both mounts in place. I have a card board covering for the rear louver.

The rest is very straight forward. I was really excited to see the wing on the mounts on the car. Granted it is just resting on the mounts, but that's not a big deal.

Yes!

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.