On Wednesday, I introduced you to my Mustang II and described some of its unique features. Today, I’m going to show some of the work it took just to upgrade the driveline. This story may not be for everyone, but it represents eight months of my life, and after such a commitment, I felt the need to share. Mustang Soul Survivor
I would also like to take this opportunity to shout out to my buddy Paul Regner. All the work on this project was done at his house, and without his help it would not have happened. Adding to the challenge, we did all the work with the car in his driveway on ramps and a pair of jack stands. Not too shabby for a pair of fifty-somethings!
As you may recall, I replaced the carbureted 2.8 L V-6 and Borg Warner four speed (the SR-4) with a fuel injected 2.9 liter V-6 and Borg Warner five speed manual transmission (the T-5). The 2.9 shares the same block with the 2.8, so the engine swap was literally bolt in. Other than hanging a wire harness to run the fuel injection system, the engine swap posed no real challenges. In contrast, the transmission work forced me to assemble a new unit using major parts out of three different car lines, and required me to invent my own transmission spacer.
On paper, the work looks pretty simple. Both transmission cases include a Ford part number, they share similar dimensions, and both use a top-loader main case with a single internal selector rod. Even better, both transmissions used a common bolt pattern on the front of the case, which led me to think I could bolt the T-5 up to the existing bell housing.
Based on that information, it looked like a weekend project. However, as I gathered the pieces to complete the project, I discovered there are a lot a factors involved, and there was no off-the-shelf solution.
Before beginning this project, I had a number of outcomes in mind:
1) With the seat adjusted for my height, the factory shifter location was a little too far forward, so I wanted to maintain the existing location. Ideally, I would have liked to move the shift lever further rearward, but that did not happen.
2) I wanted to maintain the existing clutch linkage (if possible), in order to maintain factory operation and reliability.
3) I liked the existing gear ratios, so I wanted to maintain the factory ratios in the new transmission.
4) I wanted to maintain or improve my existing shift quality. The engine bay isn’t packing huge torque, so upgrading to one of the high torque aftermarket manual transmissions wasn’t necessary.
5) I wanted to do this all on the cheap. While I’m willing to pay for quality, the list price of some aftermarket transmissions exceed the book value of the car. It’s hard to justify spending $5,000 on a $2,500 car.
Ford bolted three different five-speed transmissions to the 2.9 (or 4.0) liter Cologne V-6: the Borg-Warner T-5; the Mazda M5OD; and the Mitsubishi FM-132. Regrettably, all three transmissions used a hydraulic mechanism to release the throw-out bearing, rather than the cable system used in my Mustang. I could adapt the T-5 to my bell housing, but the Japanese cases both used unique bell housings which would not accept the Mustang II’s clutch linkage. In the end, the T-5 offered improved shifting over the older four speed unit, could use the existing clutch linkage and was available in the junkyards with multiple gear ratio options. Based on all those factors, the T-5 appeared to be my best option.
With that decision made, I looked into the best option in terms of gear ratios and case dimensions. Based on shifter placement and gear ratios, the T-5 used in early 80’s F-Bodies with the (GM) 2.8 V-6 looked good. The gear ratios for first through fourth matched my current transmission perfectly, and the shifter mounted at the very back of the tail shaft, for the best shifter placement. Looking around the local junkyards, I found one in a Firebird priced at $155 and after spending a couple of greasy hours at the yard, I thought I had come home with right the transmission.
Another fun fact- In order to match up the F-body transmission to a Ford bell housing, I needed to swap out the Chevy main case to change the bolt pattern. Jeep and Ford main cases both bolted up to the Ford bell housing, so I found a Jeep case on E-Bay to solve that minor set back.
Based on the tape measure, there were several critical dimensional differences between the original transmission and this T-5. First, the T-5 was about an inch shorter in overall length. Second, the shifter placement moved forward two and a half inches as compared to the original transmission. Lastly, the input shaft on the T-5 was about 1″ shorter than on the original transmission. While the differences were all relatively small, it meant my T-5 wouldn’t properly mate to the clutch and flywheel, would place the shifter too far forward, and would require a longer driveshaft. So much for a simple project!
This picture from the net shows what can happen if you don’t watch your lengths. As you can see, the shifter on this II is VERY close to the radio. In addition to the interference issues, this shifter requires monkey arms to reach fifth gear. After researching other Mustang II T-5 swaps on the internet, I determined my bell housing was the primary issue. It was much deeper than the bell housings on newer cars, and no American T-5 came with an input shaft deep enough to mate to it.
I found several articles about Mustang II T-5s on the internet, but the solutions I found often involved compromises I didn’t care to make. In some cases, the input shaft did not fully engage the clutch plate, and in every case, the shift handle moved forward on the transmission tunnel. In fact, several people built custom shaft levers, just to clear the radio faceplate! I needed a different solution, and thanks to the internet, I found one.
During my research on the T-5, I found a chart listing the various input shaft lengths. As you can see, almost every car uses a unique input shaft. I was looking for shaft at least 9 -1/4′ long, and nothing here in the US matched up. However, the Holden Commodore built in Australia exceeded my needs by a comfortable margin. After making a few phone calls, I found a Transmission shop in New South Wales that sold me a used shaft for $75, with shipping costs that barely made me scream.
Here’s a picture of some T-5 input shafts. Starting from the left, we have a 280Z T-5 part, a shaft out of a Fox Body Mustang T-5, the original shaft from the Mustang II four speed, and the Commodore solution. Clearly, the Commodore shaft includes enough length to fit the Mustang II’s bell housing. Unfortunately, the gear tooth count on this shaft did not match up to the gear set in the Camaro transmission. Because of that, I ended up getting a second T-5 out of a Fox body Mustang. The gear set differed slightly from my old transmission, but allowed the use of the Commodore input shaft. Once it arrived, I installed it in the new T-5 and mated things up.
As this picture shows, the shaft extended well past the face of the bell housing. Clearly, I could now mate the transmission up to the clutch plate. However, I now needed to space the transmission back from the bell housing. On the upside, the new shaft would place the shifter in the correct location on the transmission tunnel.
This photo shows better shows the new challenge. To accept the Commodore input shaft, I needed to move the transmission back about 2 1/2″.
To make this happen, I cut 2-1/2″ off the front of the old four speed transmission.
By placing this spacer between the bell housing and transmission, I maintained the factory throw-out bearing and clutch linkage, and the case bearing provided a perfect centering guide for the bearing retainer on the T-5. I didn’t even have to cut down the Fox body bearing retainer–it was the perfect length to mate with the spacer!
Here’s an image of the bell housing, spacer and T-5 transmission on the bench . As you can see, the parts look like they belong together, and line up perfectly.
Finally, here’s the base of the shifter handle in the tunnel opening. As you can see, it also matches perfectly. It took a ton of research and effort, but I did not have to compromise on shifter placement, which I consider a major victory!
From here, the project was very simple. I had a shop shorten the existing driveshaft 1″ (my new input shaft and spacer turned my too short driveshaft into a too long shaft), and my buddy Paul welded up a very lovely transmission mount to mate the T-5 to the existing hard points in the body.
That’s the story of the transmission in a nutshell. There were a few more twists and turns I chose to leave out, including a false start with a 280Z input shaft and a pile of leftover parts. But they didn’t apply to the final result, so I skipped over them.
So you may ask, was the effort worth it? As measured in the real word, probably not. The work is buried under the car, and leaves the exterior looking perfectly stock, so most people have no idea how much work this project took. In addition, I’ve invested a ton on time and money into a car that will never increase much in value, so from a dollar and cents standpoint, the project is also hard to justify. But having said all that, I’ve derived huge satisfaction from this job. Having a fifth gear makes the car five times more pleasant on the highway, and I bought the car to drive.
Would I do it again? Only after I build a shop with a lift and purchase a full set of fabrication tools!
A closing note: On Wednesday night, the Soul Survivor and I successfully arrived in Las Vegas for the Mustang’s fiftieth anniversary. While I’ll check into your comments when I can, the lures of Sin City will undoubtedly keep me away from the computer for most of Friday. For those of you with questions, the answers will come in the fullness of time.