Mark Kovalsky
Active member
If you have enough time and money it is possible to put ANY transmission in ANY truck with ANY engine.
Here's why it isn't practical.
You can have an adapter made so you can attach it to the engine. This should't cost more than a grand or two. Pocket change for a swap this complicated.
Then you'll need a wiring harness. There is no harness made that works for a 7.3L/5R110. You'll need to make one. Also an easy part of this swap.
The easiest part is the driveshaft(s.) If it is a 4x2 you'll only need to shorten one, because the 5R110 is longer. If it is a 4x4 you'll need to shorten the rear and lengthen the front. A good driveshaft shop can do both for a good part of a grand. Once again, still a cheap part.
Now comes the good part. What are you going to do about a computer to run this? Without a computer the 5R110 will always be in overdrive with the converter unlocked. It won't shift at all. There is no computer that will run a 7.3L/5R110 combination, so you will need to design and build one, along with the software to run it. This is where you run into a cost that is many times higher than the cost of a brand new truck.
There are aftermarket transmission controllers. Here's an article I wrote about why I don't think they will work very well.
It's WAY harder to make software shift a TorqShift than a 4R100, due to the design of the two transmissions.
The 4R100 is an all non-synchronous design. This means that for each upshift all that happens is a clutch is applied. All you need to do is control the pressure to the oncoming clutch and you're all set.
The TorqShift is MUCH more complicated. The 1-2 and 5-6 shifts are the same, they are non-synchronous and all you need to do is control the pressure of the OD clutch. The other shifts are the problem.
The 2-3 is a swap shift. This is a special category of difficult shift. I believe Ford is the only trans maker in the world that still does swap shifts. Others have put swap shift transmissions in production and then replaced them within a few years. To make a swap shift the TorqShift needs to release the OD clutch to downshift the OD gearset while applying the intermediate clutch to upshift the Simpson planetary gearset. This is an upshift and a downshift occurring at the same time in the same trans. From my experience these two shifts MUST complete within 30 milliseconds of each other or it's going to feel awful. If the OD releases too soon the engine speed will flare. The amount of flare is dependent on how much sooner it completes. If it completes before the intermediate has enough capacity the trans goes back to first gear! Then it has to make a 1-3 shift. A few WOT 1-3 shifts means the trans comes out to replace the intermediate clutch. Been there, done that. If the OD releases after the intermediate comes on you end up in 4th gear (1.09:1 ratio) then downshift back to third gear (1.54:1 ratio.) Either way it's really bad.
Now if you made it though that you need to make a 3-5 shift. 4th gear is the 1.09:1 ratio that really isn't used. The 3-5 is a synchronous shift. It's timing requirements are about the same as the swap shift, but there is no downshift. To make the shift the intermediate clutch has to release while the direct clutch applies. If the intermediate releases too soon you get an engine speed flare. If the intermediate releases too late you get a tie up. A tie up is when all three pieces of the planetary gear set are held from turning. This means the output shaft of the trans STOPS. That's not a pleasant thing to have happen when you're at WOT making a 3-5 shift. You can lock the wheels on an upshift! I've done this, too. You can also break expen$ive parts doing a tie up. Been there, done that, too.
Now start thinking of the combination shifts that can happen. How about cruising at 55 MPH behind some slow poke on a two lane road? A passing zone opens and you floor it. Now you may want to go from 6th to 3rd gear. You need to release both the overdrive and direct clutches and apply the intermediate. That's a synchronous shift in reverse.
As you can see from just these few examples it isn't a trivial task to make one of these transmissions shift. It's what I did at Ford for quite a few years, three of them working on the TorqShift. I'd be really surprised if anyone makes a controller for the TorqShift that works really well. I think someone could make one that does some basic shifting, but getting one so that it shifts at least as well as a stock trans is going to be a HUGE task.
