build diary

May 11, 2005:
Hmm.
This Miata badge is shaped perfectly to fit on the nose. I'm not sure if I should stick it on or not.
entry 855
Gettin' shined up for the Miata meet.
I didn't bother doing this for the track, but then again that tow through the rain to California would have ruined my best efforts regardless. This is simply the result of a bit of work with Nevr Dull.
entry 856

May 16, 2005:
If I didn't listen to the voices in my head, maybe I would have driven the Seven home from Moab.
Sigh. The CMC curse has finally struck.

The weekend started off a bit rough. While preparing Janel's Miata for the trip (new springs, shock mounts, exhaust - you know, little stuff) I noticed her supercharger belt was making dust. So I tightened it. That broke on Friday night so Saturday morning was spent putting on a new one. Finally, a couple of hours late, we took off to Utah. The belt broke again about 75 miles later - it seems I have some investigation to do into the superchager. I was happy and unaware of this problem as we zipped down the interstate and then on to the classic 128 into Moab. On the highway, the Seven is remarkably comfortable. The suspension eats up all bumps and undulations. I had earbud headphones on to listen to music so the exhaust noise wasn't bad, and other than high pressure air trying to inflate my left nostril the aerodynamics were good. Without some sort of earplugs the exhaust is loud, though. The new muffler is not as effective as the previous one, particularly at full throttle. On the twisty bits I felt as if we were almost walking although Jeremy and I did get a chance to play for a bit. I also found out that I should not lead a group without a working speedometer, as my estimated 45 mph turned out to be closer to 65. The police officer going the other way merely flickered his lights and gestured for us to slow down. Whew!

The event itself was fun. Lots of shiny cars and the new 2006 Miata was in attendance. I crawled all over that one as you might imagine and managed to take some photos with the Seven. The average attendee at the event was older and more interested in cruising and scenery than performance, but once I took the hood off the Seven so they could see the Miata engine I was a little more accepted. In the evening we took a run up to Fisher Towers and a few miles down a rough dirt road. It's a great place for taking photos of cars near sunset and I availed myself of the opportunity to fire off quite a few frames. I also rattled the exhaust pipes free of the collector and popped an exhaust hanger. Not such a good plan and very noisy although it was easy to fix. Jeremy and I then headed for a campsite as Janel went back home due to her brother's graduation.

The next day, we were lining up to go on a tour with a group going into the Canyonlands park. I stalled the cold Seven in the parking lot in front of everyone. This got me some teasing about a "poor first impression" - so I decided to give a different one by offering a taste of some tire spin. Nothing major (less than I've used in an autocross start)...but when I was done there was a ticking from the rear end. It sounded like a flange hitting as the differential turned. Uhoh. Nothing was visible so I backed the car up on to some trailer ramps. The diff had shifted a bit and some feeling around indicated that perhaps I'd ripped the diff mount off the frame. With a bit of prying I could drive the car without noise, but the diff was definitely moving up and down. My car lasted longer than any of the other CMC "Miata" frames without this failure but it's my turn now.

Lucky for me, Joe Portas (the Knobmeister - if you need custom engraving, shift knobs or other bits talk to him!) was just packing up to head home to Littleton and trailer his Miata. He offered the use of the trailer to get me home to Grand Junction. His wife Mary was quite happy with the arrangement as that meant she got to drive the Miata instead of riding in the tow vehicle. I had a comfy ride home with good company as Joe and I have been seeing each other for years at Miata meets all over the world. It all worked out well.

So, what now? The Seven was almost ready for some relatively major work anyhow. I'll put it back up in the air and sort out the differential mount. I'm not sure if I'll do the pseudo-PPF as CMC ended up as I don't think any of those cars have ever actually run. The solution that BSI worked out for the GRM car is tempting and easier to reach. Regardless, the seats are coming out. I'll make a new transmission tunnel cover, add some switches for wipers, fit an electronic speedometer driver, reroute a front brake line, make a better headlight mounting system, add a master power switch and generally do a number of jobs that have been accumulating. I have quite a list.
entry 857

On the way in to Moab for the Miata meet.
This is on route 128 along the Colorado River. Janel and her beloved blue Miata (the support car!) are getting ready for the warm weather and beautiful scenery. There are some snow covered mountains in the background but I overexposed the sky.
entry 858
I don't take many photos of the back of the car.
I'm not sure why.
entry 859
The 2006 Miata was at the meet.
During a brief lull (it was usually covered in Miata owners and the accompanying drool) I managed to park the Seven next to it. Very different cars.
entry 860
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.
entry 861
The morning sun on our campsite.
entry 862
Artsy night shot!
While taking this, the hazard flashers came on. Why? Perhaps the Seven felt it would have more artistic merit that way.
entry 863
Offroading in Moab can be pretty.
And fun - the Seven does pretty good handbrake turns.
entry 864
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.
entry 865
Fisher Tower and the Seven.
entry 866
Small car, big country.
entry 867

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.
entry 868

Courtesy of Jeremy Ferber, here's how my Moab trip ended.
entry 869
An ignominious end to a promising weekend.
entry 870

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.
entry 871

The failed differential mount.
Some parts are bent, some are torn.
entry 872
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.
entry 873
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.
entry 874
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.
entry 875
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