BD Pressure Lock with Gearvendor

[Archive]

I had two problems with my Pressure lock from BD. First, I started getting check engine codes. To fix that I installed their driver kit for the 24 Valve applications.

On my last trip I then noticed that sometimes the pressure lock worked and sometimes it didn't. (You can feel the easing of spring pressure on the throttle when the cylinder activates the pressurelock). This can be very bad since if it doesn't activate the cylinder at WOT with enhanced power, you will defenitly slip the tc clutch.

Today I solved both problems (I think). The signal to lock up the clutch is the absense of 12 VDC. When operating the BD manual lock-up switch the voltage dropped to .55 Volts and the driver to the pressure lock solenoid worked properly. When the BD switch was left in the other two positions, the lockup signal read .95 volts which is too high to trigger the driver for the pressure lock solenoid. .65 to .7 volts is the normal threshold for an NPN transistor (for those who are electronically inclined). I disconnected the driver and the pressure lock activates every time.

Second (or first problem) I did not install the resistor suggested by BD should the truck revert to "limp home mode". Since it didn't, I didn't. Today I installed the resistor and measured the voltage on Pin 31 of the PCM. Sure enough, 5.2 volts. BD states in the instructions that 5.0 volts is the max. Although 5.2 Volts does not sound like enough to cause a malfunction, I don't know what the internal voltage is, nor what the 5.2 volts might reach under various operating conditions. I do know that if one input gets overvoltage on a computer chip it can result in unpredictable and sometimes very strange results.

Everything feels real solid now.

Sorry for this long and convoluted post. Bottom line: I believe the resistor should be added whether you see problems or not. If you use the driver for the solenoid and have any other equipment that effects the tc signal, make sure the voltage to the driver is always under .6 volts when in lock-up.

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John S. '99 QC 1T 4.11 A/T Leather Driftwood, 50 Gal aux tank/tool box, gearvendors, BD brake/autolok, BD ISB comp, guages, BD Pressure Lock and Pract. Sol. Boost Elbow.

Just a Little BOMBed and liking it a lot.