Terry, I just recently installed the Smartbox and haven't towed with it yet but I'll tell you what I know.
Installation is easy if you can do wiring and aren't colorblind. There are a lot of wires. The main cable bundle runs through the firewall and is about 8 - 10 ft long. Most wires connect to the tcm wiring near the airbox and several under the dash. I ran the cable bundle under the carpet next to the driver door and under the driver seat, through the carpet hole where the existing power seat wires are. The cable is long enough to allow the Smartbox to be held on the center console for adjustment while driving and then put under the seat when finished. The operation is adjustable for lock and unlock speeds according to your preference. I have my exhaust brake on a separate switch so I can run with both Smartbox and brake off or Smartbox on and brake off. I will only use the exhaust brake when towing. My primary reason for the Smartbox is the TC saver function.
This is how it works. Acceleration is the pretty much the same thru the gears and lockup. When cruising above 50 mph and let up on the accelerator the TC remains locked and you get engine braking ( just like a manual transmission - if the exhaust brake is on you will slow a lot quicker - otherwise it is just normal engine back pressure ) when the speed get to 50 MPH (adjustable) the OD turns off and shifts into 3rd lockup and more braking, then into 2nd lockup more braking and unlocks at 18 MPH. OD is now off and you have to push the OD button when back up to speed. 2nd gear lockup just locks up the TC when in manual 2nd above 18 MPH.
The TC saver function unlocks the TC anytime you depress the accelerator more than halfway. Works just like a passing gear and saves the TC clutch from high power surges.
I have to add a disclaimer here as I haven't used it a lot and my TC saver adjustment doesn't have a wide enough range for my truck. Bill is sending me another box that has a different TPC adjustment range. Some older 24v trucks have a different TPC voltage.
In my opinion this box is a must if you have an exhaust brake and if you don't have an exhaust brake at least get the TC saver.
Hope this helps. Tom
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Tom W in Austin Tx 98 24v 2500 Quadcab, auto, 3. 54, lsd, Rhino, white/driftwood, Banks Stinger Plus, 275 injectors, Manix grill, nerf bars , DTT's TC, valvebody, cooler, Smartbox, Mag-hytec trans & diff, Pac brake, Bilsteins.
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