realsquash

Vehicle speed shouldn't be required to run the engine nor the tranny. Unplug your VSS and see what happens.

Andy

AK RAM

Vehicle speed is used to compute how various things react. Transmission shifting and lock-up are among them. As far as I know, Torque Management is only prevalent on trucks with the 47RE transmission (01? thru 03). Manuals don't have it at all, regardless of the engine. The top speed limiter is something different. TM is simply defueling to protect the weaker 47RE during shifts. It also limits the amount of torque the engine can produce without picking up speed, i.e., when building boost at the line. TM turns off as soon as the converter locks in 3rd (overdrive off) or 4th. Not to say the 04s don't have it (not 100% sure), but if they do, you will never notice it. I have never noticed TM in any truck with the 48RE trans. You can definitely feel it, big time. You would have to go for a 1/4 mile ride in my truck to see exactly what torque management does. With my truck in it's 12.9 second 1/4 mile configuration, it won't break 15 seconds unless I turn off TM. It limits power that much. TM is worse on the 03 SOs verses older year trucks with the 47RE because of the engine rating (higher than the 02 HOs) and because the 03s are so much heavier. They thought the 03 47RE would need more protection. Makes for a good automatic valet switch though.

I think the 04s are a little different than the 03s and that complicates things. I have an ECM which controls the engine and a PCM which controls the transmission. I think sometime in 04 they went with just the ECM doing both and you no longer have a PCM. The RAD splices into two wires in your communication buss bundle. One is the VSS and the other I can't remember the technical name for, but basically interrupts the TACH signal. Both of these wires have several "Ys" to them that go to different parts of the engine. The wires that go to the ECM are used to compute how TM affects your truck. However, the other side of the "Y" goes to the PCM, so trans operation is not affected as it is still getting the info it needs to shift correctly (if that makes sense). These wires have to be spliced into at the right spot or things stop working. Since the 04s don't have a PCM (I don't think), you would be cutting the only signal that controls everything and would really have problems I would think.

Before I put the RAD on, I cut these wires to see if I could do the same thing as the RAD without spending $250. It didn't work. The truck dies as soon as you cut the TACH signal (with a toggle switch). The RAD is an electronic box that mounts under your dash and is doing a lot of "fooling", not just cutting a signal. Nothing happened when I cut the VSS to the ECM other than a check engine light, but I didn't drive it to see how it shifted. I just put the RAD on at that point. On an 03 truck, I can cut the VSS going to the ECM, and the PCM, which controls my transmission, is still getting it's signal from the "Y". I believe if you cut the VSS on an 04, the trans probably won't shift correctly as it is needed for proper trans operation.

I would think that turning the key to the sweet spot is just cutting power to your gauge cluster. If the tach signal was actually lost, I don't think the truck would run and you will definitely get codes. Just guessing.