build diary

May 16, 2005:
Camping in Moab with Jeremy from Flyin' Miata.
It was a challenge to get the Seven in to this campsite. It's not a great off-roader.
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The morning sun on our campsite.
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Artsy night shot!
While taking this, the hazard flashers came on. Why? Perhaps the Seven felt it would have more artistic merit that way.
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Offroading in Moab can be pretty.
And fun - the Seven does pretty good handbrake turns.
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I took a lot of photos of the car with the rocks in the background.
I'm not even going to try to justify it.
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Fisher Tower and the Seven.
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Small car, big country.
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May 17, 2005:
Tonight I should be able to put the car up in the air and pull the transmission cover off.
First the seats have to come out. Then I'll know just what has failed and how. I'll also have a better idea of how I can fix the failure. Thinking about it, I suspect my long bolt has simply dropped out of the slotted hole that was in the upper transmission mount. The mount was too far forward. We'll see. No matter what, I'll fix this so it can't happen again.

Since I will have the cover off the transmission tunnel I'm also going to install a new speedometer drive. The 1999 and later Miatas use an electronically driven speedo instead of the cable driven one I have now. The packaging of the transmission is such that the cable has to bend radically shortly after exiting the transmission and the first one lasted 10 miles. A new cable is obviously not the answer so I'll have to see if I can somehow manage to install and drive a later speedo. I've found a junkyard instrument cluster with some damage to the housing, perfect for my intentions.
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Courtesy of Jeremy Ferber, here's how my Moab trip ended.
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An ignominious end to a promising weekend.
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May 19, 2005:
The transmission cover is off and now the failure is visible.
The ticking noise that alerted me to the problem turns out to have been part of the parking brake assembly bouncing off the pinion flange. CMC had reported a clicking noise and loss of drive and I'd never understood where it came from. The clicking, okay. The loss of drive is still a puzzle of course.

The failure itself was the mounting bracket on the transmission tunnel. The bolt holding the diff in place was only in contact with a small area of the bracket as this was too far forward. As the diff strained to move up and down, it tore the bracket apart. It's quite possible this was a slow-motion failure that only made itself known after the diff had lifted enough to contact the parking brake.

Solutions? I have three options right now. One is to copy what CMC ended up doing and build a tubular version of the PPF. Heikki has some photos of this on his site. It will have to wiggle around the edge of the transmission tunnel and driveshaft flange but it should be possible. It doesn't look compatible with a handbrake, though. One way to make this easier would be to put a plate on the side of the transmission tunnel instead of the tubes. This would open up 3/4" or so of width and I'd probably still be able to work out a way to attach the handbrake. I don't think any cars with this solution have turned a wheel yet although it certainly should work well.

Another option would be to copy the solution developed by BSI and used on the GRM car. Again, that car hasn't really been run hard. I'd be concerned with the welded tube coming off the back of the diff but it sure would make life easy. I suspect the weight would be less than the PPF solution as well.

The third option would be to simply reinforce the bracket at the nose of the diff. Instead of a thin piece of about 1/8" plate, I'd put in something stronger. It would also be a properly located hole instead of a half-engaged slot. An extra tube would be run straight down from the side of the bracket to ensure it was well supported - possibly a plate. This might be the easiest and lightest solution. Given the amount of abuse my original setup endured I believe this would probably work well - but I do have plans to increase the horsepower of the car at some point.

I've also decided to add some stiffer bushings in the side mounts for the diff. They are able to rock back and forth a fair bit. I might also bolt on a piece of C channel to hold the other end of the bolt in place. At the moment it won't move with the diff but that will change with stiffer bushings.
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The failed differential mount.
Some parts are bent, some are torn.
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Viewed from above.
It's obvious that the diff was only mounting to a small section of this bracket. It's no wonder it failed. One suggestion has been to simply reinforce this mount to prevent cracking.
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The entire transmission tunnel.
Trying to put a PPF substitute in place will be a challenge to fit. The brace would have to go past the flange (underneath the handbrake T) and then dodge around the bars on the side of the tunnel.
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The solution designed by BSI for Grassroots Motorsports.
It would be easy to do without disassembling the car, but my car is already pulled apart. This photo is from the December 2004 issue.
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May 24, 2005:
I had a busy weekend working on everything but the Seven.
You'll be glad to know that the supercharged Miata is now happy again, my street Miata is equipped with wipers and a heater now and the GTX has a boost gauge and Momo steering wheel. That doesn't mean I wasn't thinking about the Seven, though. I've ordered some 30% stiffer springs from GAZ to allow me to play with the handling a little. Some stiffer rear differential bushings should be on the way in a few days. The down side is that I'll have to pull the diff out to install these and that is a royal pain in the butt. I'm starting to work out how I'll mount the diff. First I need to pull off the rear bulkhead panel so I can get a better look at what's under there.
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May 27, 2005:
Did you know it's possible to put Protege5 struts on a 323 GTX? No? Well, it's not exactly a bolt-on with all sorts of cutting, welding, drilling and grinding involved.
This project has kept me busy for the past few days. The car is transformed though. I'm sure all the home-built car fans are happy to hear that.

On the Seven front, I've obtained an instrument cluster from a 2001 Miata so I can use the electronic speedometer and replace my broken cable. This should be an interesting swap but I'll make it work. Somehow. The differential will get some attention shortly. I'll pull the rear bulkhead apart this weekend and come up with a final solution.
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While the transmission is uncovered, I'm going to see if I can replace my mechanically driven speedometer (well, it would be mechanically driven if the cable would stop snapping) with this electrically driven one from a 2001 Miata.
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May 31, 2005:
I think I'm going to start customising bicycles instead of cars.
They're cheaper and easier to put together. Janel and I are working on a super-cool satin black hot-rod of a cruiser right now. Does it seem as if I'm avoiding the Seven? Well, maybe just a little bit. I have to get the nerve up to start working hard on it again.

The procrastination isn't complete, however. I pulled the scuttle and rear bulkhead off this past weekend. It's almost shocking how quickly I can disassemble this car and make it look unfinished. Removing the rear panel uncovered the bracing that's available back there. There's a lot of strength, more than enough to keep the diff tied down if the bracket itself is strong enough. I'll probably just build a stronger mount for the nose. The diff will have to come out in order for me to put new bushings in the side "arms", though. That's going to be a hassle as I have to wrestle with a 75 lb chunk of metal that is a tight fit into the frame. Oh well, if it was easy everyone would be doing it.

The scuttle was removed to give access to some of the wiring and the speedometer drive. The mechanical one has been removed and will be replaced with an electric one. Luckily, the gearing of the unit is the same as my car so it should be accurate. The hard part will be fitting the speedometer in the earlier housing. Well, not that hard. Again, if it was easy...
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The mechanical and electronic speedometer drives.

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The electronic speedometer (top cluster) is much smaller than the mechanical one, mostly due to the lack of a mechanical odometer.
It also has a fairly complex mounting system of molded plastic in the housing. Luckily, the electronic version is also lower profile so I can fit it inside the older cluster by simply cutting it out and finding some way to attach it inside. Wiring will be a secondary problem but a fairly simple one.
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An overall view of the structure of the rear bulkhead.
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A closer view at the structure just around the differential nose, especially considering the diff mount will basically be in the same plane as the bulkhead.
There should be enough strength in here for me to use. That's not rust in the picture, simply red Moab dust.
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The poor Seven appears to be regressing.
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Maybe I'll hang this on my wall as art.
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