copied from Mark on Powerstroke Nation.
If the shifting isn't EXACTLY right it will blow pieces all over the road. Go back up and read the long post I wrote. If you make a 3-5 shift and don't release the intermediate clutch fast enough you'll lock the output shaft to the case, and the rear wheels will stop turning for just as long as it takes to break something.
Here is his long post:
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 catagory 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 occuring 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 dependant 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.
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 the direct clutch 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.
