On my ’00 F550 I put a TCC lock up module from SP diesel, It comes with an adjustable trimmer (allows up to set lock up from 18 to 40 mph) well the trimmer dose not work it locks at 25ish mph. It was an easy install one wire hooks to a speedo wire, one to the TCC wire and the Ignition and ground. I put a switch in the TCC wire so I can shut it off.
It works well I don’t use it too much now that I have a max low stall billet multi disk torque converter. This new torque converter was a great upgrade less than $500
Ford Heavy Duty Torque Converters by Precision of New Hampton, Inc.
The only issue is the “OD OFF” light will flash when is commands NO lock up and the TCC solenoid is still grounded. But no limp mode.
On my ’97 I just put a switch with one side grounded and the other going to the TCC wire you just need to shut it off when you come to a stop. I needed to do this with the ’97 because I need to lock in 1st gear.
The reason to manual lock in 1st is because the road to my farm is rough and windy with a one steep hill and when pulling hay or horses I cannot get a run up the hill so I am in 1st gear full throttle for about 1 mile.
The OBS truck will not lock up in 1st gear (SD dose at 75% + throttle). With out lock up my TCT is at 250* to 280* by the time I get in to my driveway. If I lock TCC and pull the hill (no need for full throttle) the TCT is 140* to 180*
I have read it is not good to lock in first but I never do it at low RPM
The lock up switch will really save a stock converter IMHO