OBDII mods using ECM and toggle switches?

[pacificdrumma]

Want to get some answers to a couple questions regarding toggle switch mods to an OBDII ecm. I know about the high idle switches, but I had two other questions to ask as well. From what I have heard, the B&M shift kit is nothing more than a toggle to the ecm just like the high idle switches. Is that true? And if so, can it be done with a standard toggle switch? Next is the torque converter lockup switch. Can someone explain that to me? What does it do to help the truck, when do I use it? And lastly, I assume an inline fuse is needed, what amperage?

 

[JayTheCPA]

I’ll take the TCC question. Am going to presume there is a good understanding of when the TCC locks and unlocks on the 4L80E and why. Upfront disclaimer: do some research as using a manual TCC lock may throw codes and put the tranny into limp mode in some situations. Not looking to scare anybody out of using a TCC lock (as I found some that love it), just pointing out that the flip switch is not a 'fire-and-forget' solution.

There are two main uses of a TCC lock and both are primarily for towing: 1) lowering fluid temps when pulling long grades in lower gears / lower speeds, and 2) engine braking. If the truck is just a daily driver, adding a TCC lockup switch does not add any real benefit, so again, do research if this is really meets goals versus putting time / money into other modifications.

To the benefit of locking the TCC when pulling long grades in lower gears / slower speeds, the TCC unlocks under a set speed (commonly 50 mph for a stock ECM), when the TCC unlocks it allows slippage, this slippage creates heat by way of friction, add in moderate to high power settings from the engine, and the resulting heat buildup starts to occur quickly; locking the TCC stops the slipping, allows engine power to go directly to the wheels, and helps keeps fluid temps in check.

To the benefit of engine braking, when the TCC unlocks while slowing down it is almost like putting the 4L80E in neutral which gives little benefit and nearly all of the slowing occurs from the friction brakes; locking the TCC keeps the engine in play and reduces the need for friction brakes. In case you have not noticed, the ECM unlocks the TCC at any speed when applying the brakes (counterintuitive, huh?).

The natural question is why not program better TCC lockup into the ECM? Answer: Have yet to find anybody that has taken on this programming challenge, but there are some re-tunes to get a little better TCC behavior.

If getting a TCC lock switch is still part of the upgrade path, recommend putting it way down the list and replacing the GM4 first :hihi:

 

[pacificdrumma]

Unless I am mistaken, a TCC lockup switch is just a toggle to put power to a terminal just like the high idle and trans switches, so theoretically I could do it whenever on the cheap right? Replacing the GM4 is on the list, fear not.

 

[JayTheCPA]

Have dug for some time and yet so see anything that simple where it looks like a circuit bord is necessary to fool another; there is a simple flip-switch solution, but again it goes to a proprietary circuit bord which fool's the vehicle's board.

This is the closest I found to get good TCC lockup across the gears:http://www.thetruckstop.us/forum/showthread.php?34326-Manual-Shift-Connection-Option-for-the-4L80E
but my read is it is either money and / or personal time to get better results without swapping out internal components.

 

[pacificdrumma]

Thanks for the help Jay!

 

[JiFaire]

You can only do the TCC toggle on an OBD-I... ( 1994, 1995). Your 1996 is an OBD-II. You will need the signal to be pulse width modulated or you risk burning out your TCC solenoid.

as for programming it into the ECM, all the guys doing reflashes do that. It is the easiest and safest way to alter the TCC lock in an OBD-II

 

[Edzzed]

the b&m shift plus is nothing more than a box with some resistors in it. It changes the values the ecm sees. You can make your own if you want.