47re down shift & converter unlock

[jlbayes]

Ok this is driving me nuts. On my 97 if you use heavy throttle it will down shift from overdrive & unlock the converter even with switches for both to force lockup & overdrive. I did replace the tps with a tps delete with no change. What does not make sense to me is it will do it regardless of the switches. Yes there is a jumper harness for the trans relay in the pdc under hood. It does have an old school dtt voltage box from a previous owner that I am thinking is going to take a permanent vacation. Truck is all stock, no power mods. Previous owner had recently replaced the electronics in the transmission. Switches are tied into the harness near the pcm.

 

[Big Blue24]

I've had some trucks come into the shop with weird tranny issues like this, some times we simply cut the wire between your lockup and/or overdrive splice/tap and the PCM to rule out a faulty PCM sending 12v down the ground signal wire and making the solenoids act weird. You can also test the resistance of the wire/lockup circuit, should see 35 to 40 ohms resistance on a healthy solenoid. Measure resistance between the 12v solenoid feed wire and one solenoid ground/activation wire. Or you can measure resistance across your two ground circuits running up from lockup and overdrive, you should see double the resistance when you measure across the ground legs from both solenoids so 70 to 80 ohms. You might unplug the PCM when checking resistance so it doesn't mess with the test because the factory wires do run back to the PCM obviously. You might simply have a bad set of solenoids that need to be replaced. I've also seen trucks with "nifty" light-up lockup and OD toggle switches that have poor ampacity and don't fully energize the solenoids so without the PCM also commanding lockup or overdrive, it will kick out when you wack the throttle.

 

[jlbayes]

I will check them. I did unhook the dtt box last night and so far so good. Saw some OLD threads floating around from TDR and bombers about them causing issues.