'73 Vega GT All Aluminum Wildcat 355 Project

Contents:
Page 1: Engine Block prep
Page 2: Head mods
Page 3: Induction/Exhaust
Page 4: Engine Assembly
Page 5: Front Suspension Mods
Page 6: Rear Suspension/Weight Transfer Mods
Page 7: Rust Repair and Undercarriage prep
Page 8: Frame Rail fabrication/Unibody support
Page 9: Body Mods
Page 10: Transmission Mods
Page 11: T5 Rebuild
Page 12: BMW Radiator Swap

Transmission:

I initially planned on using the stock saginaw-4 (bolt pattern bellow ) that came with the Vega. It's not bad and can take some pretty decent abuse. I recently discovered, however the T5 is an option for me. Borg/Warner made the T5 for a number of GM cars including the F-bodies, Chevettes, S10 series trucks, and Astro Vans. They made the "350MT" case pattern and register diameter until the mid-nineties. (above ) That is the same manual case pattern from the M20/M22. Pix from Wilcap

After lots of research I decided to upgrade a T5 using a Straight-cut Dog-ring kit from G-Force Transmissions. Here's a couple pix. The kit only works with a "World Class" T5. This means that the 1st, 2nd, and 3rd speed

gears riding on roller bearings instead of solid shafts. The countergears are upgraded to tapered bearings. The bronze synchro rings were replaced by fiber lined rings and dual cone designed rings to improve ring surface area.

SO the first step was to get the right T5 without spending too much. Since I planned on upgrading the internals, including the input shaft, I had the option to buy a World Class "WC" T5 from a V6 Camaro. It has the less popular 14-spline input shaft.

The unit I bought was not advertised as a WC unit. It's important to do your research and look for the clues that tell you what the T5 is. In this case I saw the yellow and black Dexron II only sticker on the side:
Another clue is the bearing plug right under the input shaft (pictured left. taken from Ford Muscle ). The WC T5 has a hardened bearing race cap visible here. It is a pretty distinct ring with "Timken" and a part number etched on it.

This is a dead give-away. On a NonWC T5 this is something that resembles a freeze-plug inserted backwards. It's a little convex and smooth. I didn't have the pictures of the input shaft to be certain and I didn't want to advertise that it was a WC with a question to the seller so I relied on the Dexron II sicker. Chances are if it has this sticker it's a WC T5.

Here's a link to a great article about T5 identification I found at BritishV8.org . For all you Vega guys out there heres some pix of the Saginaw-4 and T5 side/side. There will be some fitment issues. For one the tailshaft housing is 3 in. longer. I'm not certain how long the driveshaft is for the T50 5-speed that came stock with the Monza/Vega but it's likely I will need to have the driveshaft shortened.

The mount location is different so an adapter will need to be fabricated. I have also purchased a "Ford" tailshaft housing for two reasons. Here you can see that the mounting location is not only better but is also not tilted at an angle like the Camaro rear mount. All F-body T5's have this angled mount since they are all mounted at a 15º angle on the bellhousing to give a better shifter location. There also is a provision for a torque-arm mounting location on the "Ford" tailhousing that is also mounted straight. The other reason to swap to the "Ford" tailhousing is the shifter location. It is a few inches farther forward than the F-body shifter location. The tailshafts are almost the same length and should swap. I will see if this is possible and post my results.

A possible problem is the input shaft length. The stock Saginaw-4 input shaft looks about 6.75" long. The T5 looks about 7.25" long. Hmmmm. I hope this will not be a problem. I'm also not certain if the input shaft lengths are different between the 14-spline and 26-spline. That is possible...

Just for confirmation here is a couple pix of the T5 on my very rare Buick 215/Rover bellhousing. I was really concerned that it wouldn't fit but it does, perfectly! OH one more thing to add: The difference in weight is gigantic! I weighed them personally.

Saginaw-4: 105 lbs.
T5: 74 lbs.

Both dry. That's a difference of over 30 lbs.!! That goes a long way to reducing weight.

I got my new Straight-cut Dog-ring kit from G-Force Transmissions. They look great! The ratio I went with was the stock ratios for the f-bodies:

1st: 2.94
2nd: 1.94
3rd: 1.34
4th: 1.00

5th: 0.59 (I reused the stock OD gear set)

To mount the T5 in the Vega I needed to modify the stock crossmember to allow for a further aft mounting position. I also needed to lower the mounting point about ≈1", a little less, because I lowered the engine by about 1.5". I wanted to reduce the engine angle a little for better carb leveling.

What I did was cut the center out of the stock crossmember equal distance from the ends. Then I swapped the sides of the mounts so the arms swept backwards instead of forwards. Then I angled the two sides down to meet up with the lower center section and tacked it into place. Then I added pieces to flesh out the construct. It worked out pretty good. I'm getting better at fabrication.

Next I fabricated a base to adapt the Saginaw trans mount for the crossmember. The Ford tailhousing leaves about a 5º angle on the base. SO I made a wedge and welded a plate to attach the mount.

Here's what the crossmember looks like with the mount attached. It looks pretty good.

Here's what it looks like with the trans installed with the crossmember hooked up in it's final location. Here's a shot of the T5 looking down the tunnel at it's finished position.

I went shopping for my clutch. I figure I will likely get the CenterForce clutch. I've got a couple numbers here: Dual friction: DF161675
Centerforce II: CFT361675, 384161