Vintage Thunderbird Club International

It looks like both the brake cables and the exhaust pipes are going to need some modification

So far, so good. When I put the headers on, the engine mounts were shimmed up in the front about 3/16ths. I think that is benefiting me now because lifting in the front tilts it down a little bit in the back, and I haven't reinstalled the transmission mount yet, but it looks like it will just barely fit. It has less than a 1/4" all the way around between the exterior of the GV to the sound deadener on the inside of the tunnel.

It does look like it is going to be high enough so my parking brake cables will not rub on the bottom of the GV oil pan.

Due to the tight fit, there is not enough room for the speedo cable to come straight out of the side, so the project is on hold until a 90* speedo adapter arrives.

I made more progress this week.

I had to do a little bit of griding on the front of the new transmission pan and a little bit on the X-member.

The overdrive is sitting in place and I've measured for the new driveshaft. It will have to come back out for the 90* speedo cable adapter (that costs $200!!!) because there isn't enough space for the speedo cable to make a nice even bend. I'm very happy it fits with just a tiny bit of clearance all the way around.

I had to cut out the old exhaust and start over, what you see in these pictures is just sitting in place.

I will have to lower the parking brake cables about 2" so they can ride nicely between the X-pipe and the oil pan on the overdrive unit. So far so good.

Here is a shortened driveshaft next to the stock driveshaft. Notice the slip yoke is different with a larger size U-joint. The driveshaft guy said I should have upsized the u-joint on the rear axle when I had the new center section built because this one is significantly stronger than stock. I'm not drag racing this thing, and I haven't heard of too many people complaining about broken u-joints, but it would be something to consider if doing this from scratch

Here you can see the brake cables passing below the GV oil pan. They clear when the brake is off, but they rub when the brake is on. This is with a two inch drop, probably should have done a 2.5" drop. I may have to rebuild the spacer for I don't even know how many X times to give clearance. I've also ordered a block of teflon to attach to the bottom of the oil pan just in case I can't eliminate all of the rubbing.

A 90 degree speedo cable adapter is absolutely required, the cable can't make this sharp bend. This is actually the tightest clearance of the whole job, which is saying something because I've been checking clearances with a single sheet of paper. It is touching the sound deadener, but it does not seem to be a hard interference. When selecting the adapter, be sure to read the description. Most are 5/8", which is too small, I think 7/8 is the correct size (same as GM TH400). The cheaper ones are designed to attach to the speeedo and are too weak to attach directly to the transmission. I winced at how expensive this was, but it is the only part for the job.

It has been a long process, but after some other challenges I've got the car back down on the ground and I took it out for a shakedown test drive yesterday. The speedo cable is a little loose, so, I've got to correct that, but otherwise it worked nicely.

I drove about 50 miles on the highway and hills and around town in automatic mode. The overdrive doesn't kick in until about 40 MPH, so it is basically a 4-speed with 4th gear as an overdrive. Upshifting is so smooth I hardly noticed it. Downshifting is a little more abrupt, not not worse than any of the C6 shifts. So far I'm pretty happy with it. Hoping for a little better fuel mileage.

This is a slightly used unit and I got it with the control box and wiring, and I had it all hooked up, but it didn't work. I got a new controller from GV, but it is a new design, so I had to change out all of the wiring which was a real pain and probably what loosened the speedo cable which just pushes into a pocket and doesn't have anything to hold it in place. If anyone has encountered this and has an idea on how to hold it, I'm looking to make this more robust.