I'll try to keep this brief.

I have an early 1999 F-250 SD 4x4 5.4L. The torque converter self destructed 400 miles after I "bought" the truck from my father. The transmission fluid looked like red glitter paint, so the entire transmission was written off and I flushed the trans cooler very well. My dad never cashed the check I wrote him for the truck...

So I got a transmission and torque converter from a 2000 F-250 4x4 that was rolled over with 60,000 miles on it. Swapped them over realizing that one was ON/OFF and one is PWM, but it was cheap and I had gotten the truck for free at this point. I've put about 2,000 miles on the new setup, transmission works perfectly except for one minor detail. The lock up on the torque converter is noticeable and harsh during acceleration. The truck feels like it shifts through 5 gears except the TC lock up is harsh-ish. I understand how pulse width modulation works, so I understand what is happening to cause the harsh lock up.

I've done some research and have seen that the PWM transmission also use a different pump, it doesn't seem to just be a different TCC solenoid. My original game was "can I get a gas ON/OFF valve body and swap it into the transmission?" The answer appears to be no but maybe someone knows otherwise.

So now my game is either just driving it as-is, because it has cost me so little for a truck in otherwise, good shape. Or figure out a way to otherwise "trick" or control the transmission for a reasonable price. I'm only concerned with the longevity of components in an ON/OFF truck controlling a PWM TCC. I don't haul anything heavy with any kind of regularity, the truck just sees junk and motorcycle hauling with an occasional small trailer behind it. If it runs another 100,000 miles without any changes, it doesn't bother me too much.

I guess I'm basically just fishing to see what people who have dealt with these 4R100s have to say about my current set up and my options. I know I could purchase a separate transmission controller, but I'm not quite there yet.

Appreciated in advance.

 

Yes you can, but it won't make any difference. There is no difference in the valve body between on/off and PWM. There is a different solenoid and a difference in the pump body, but not in the valve body.

I don't think there will be a problem if you can live with the harsh lockups.

 

I was under the impression the TCC solenoid was in the valve body, I was mixing that up with the solenoid pack I believe.

So then, my question is, are there differences in the solenoid pack? Will the ON/OFF solenoid pack be compatible with the pump body in the PWM transmission. Or will it not make a difference and the real issue is the pump body being different?

If this was using a PWM truck to control the ON/OFF transmission, you could probably build in a circuit to effectively convert the pulsed digital signal to a solid ON/OFF, but would it be worth the trouble is the question...

Thanks for your input Mark, I appreciate your response. I've been reading a bunch of forums and was hoping I'd catch your attention.

 

There are no solenoids in the valve body.

Yes. The on/off solenoid is different than the PWM solenoid.

You won't make any difference if you only swap the solenoid. The lockups will still slam on. There is an orifice in the pump body that has to be changed. A PWM pump has a 0.250" opening, the on/off pump has a 0.030" orifice. That's the real problem, the much, much greater flow through the large opening compared to the small orifice.

Now the difference between 0.030 and 0.250 doesn't sound like much. But 0.250 is 68 times larger area than 0.030! That means it will lock the converter approximately 68 times faster. Not quite that much faster, but almost.

That's the real issue. If you change the orifice they will be identical.

 

That where I suspected we were going! Good lesson on circle surface area that everyone should remember when ordering pizza!

Thanks again Mark, I appreciate your engineering prowess and willingness to help me.