torque converter lockup mod

[Fozz]

Fozz, you do need a DPDT switch, you also need the 22k resistor - if you looked through the lockup mod threads you probably noticed some folks experiencing limp mode after they trip the switch and converter gets locked when the PCM wants it open. The resistor is used to feed alternate signal to the PCM whenever the lockup is under manual control (be it open or locked), it essentially creates a "dummy converter" so the PCM is happy and proceeds to do its thing, while you do your thing with the switch.

I researched (this site and others) and saw where some people were having the limp-mode issue, that's why I wired mine to switch to run normal in case I had an issue. Mine ran fine with no limp-mode or any 'off' lights. I just put 400 miles of some pretty hard towing (10K lbs) on long steep hills while in and out of overdrive and even shifting down to 2nd a couple of times and the mod worked perfectly. Maybe my PCM isn't as sensitive to a feedback signal or the 'issue' is for certain year trucks with slight electrical deviations?. It was sure nice having the engine braking for some of those hills.

 

[LCAM-01XA]

A few days later, but I've been pretty busy here, so sorry for the delays:

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When you cut the purple/yellow wire and extend it to the cab the end that comes from the transmission is marked in red in my diagram, and the end that goes to the PCM is in blue. Parts in gray are optional - red LED will light up when converter locks up, green LED comes on when you switch to factory PCM control.

 

[international]

Last post...file not found?

I would love to get the diagram that is no longer available on the last post! Any help?

 

[LCAM-01XA]

One diagram coming right up This is for the auto-lock setup where you can flip the switch between full PCM control of the lockup (factory settings and all) and manually locked converter. When the "manual lock" mode is selected the converter will stay locked all the time in 3rd and 4th gear regardless of whether brakes are applied or not, until you either flip the switch back to "auto" mode or slow down enough to where the transmission drops out of 3rd gear. Converter will NOT lock in 1st or 2nd gear.

Wiring code:
- purple wire with yellow tracer - responsible for TCC operation, this is the one inside the transmission harness that you cut and extend both ends and feed them into the cab, the end from the TCC goes to the relay and the end from the PCM goes to the switch.
- orange wire with yellow tracer - responsible for SS1 operation, lives in the transmission harness, however this one you do NOT cut, just a splice another wire into it and feed the new wire in the cab to the relay.
- red wire - you need to add this one, use one of these "Add-A-Circuit" fuse holders that can be found at about any decent parts store, they're good for up to 10 amps on the aux circuit but you won't be pulling even half that.
- black wire - this is the ground that will lock your converter when you select "manual lock" mode, so make sure it's grounded real good.
- gray wires - those are optional, they are for the three LEDs: red LED is on when the converter actually locks, green LED is on when you're running into "auto" mode, and yellow LED comes on to warn you the converter will not lock when the transmission is not in 3rd or 4th gear yet - basically you wait for the yellow to go off, and then switch between green ("auto" mode) and red ("manual lock mode").

 

[international]

Does anyone have a different diagram for other controls?

 

[LCAM-01XA]

You want one for the lock-auto-unlock setup? Here ya go Since this makes three modes total we need a 3-position DPDT switch, in other words an On-Off-On (also known as "center-off) DPDT switch, and to make use of its center off position we'll need another 5-pole relay as well (the switching relay in the diagram attached), and there is also a diode to prevent current from backfeeding where it don't belong:

Wiring code:
- purple wire with yellow tracer - responsible for TCC operation, this is the one inside the transmission harness that you cut and extend both ends and feed them into the cab, the end from the TCC goes to the relay and the end from the PCM goes to the switch.
- orange wire with yellow tracer - responsible for SS1 operation, lives in the transmission harness, however this one you do NOT cut, just a splice another wire into it and feed the new wire in the cab to the relay.
- red wire - you need to add this one, use one of these "Add-A-Circuit" fuse holders that can be found at about any decent parts store, they're good for up to 10 amps on the aux circuit but you won't be pulling even half that.
-green wire - you need to add this stuff too, this is for the dummy signal resistor for the PCM and also the protective diode so the switching relay don't go nuts cycling on-off-on-off when you select the "auto" mode with the switch.
- black wire - this is the ground that will lock your converter when you select "manual lock" mode, so make sure it's grounded real good.
- gray wires - those are optional, they are for the three LEDs: red LED is on when the converter locks in "manual lock" mode, blue LED is on when you're running in "manual off" mode, and yellow LED comes on to warn you the converter will not lock cause the transmission is not in 3rd or 4th gear yet - again you can wait for the yellow to go off and then switch between blue ("manual off" mode) and red ("manual lock" mode), or you can just place the switch into "auto" mode and ignore the yellow LED entirely.

 

[fury9]

OK ,proly a dumb question but, will this only allow tc lock-up in OD? Or are the shifts from 2-3 or 3-od or vice-versa full tc locked shifts or downshifts?

 

[LCAM-01XA]

Both of these setups completely override the PCM's control of the converter lockup, meaning you can lock and unlock the converter whenever you want to. What I usually do is leave the converter unlocked till I'm near the cruise speed I like for the road conditions and then lock it, for instance if the speed limit is 45 mph I'll lock out the OD and then shift 1-2-3 and then lock the converter still in 3rd and cruise like that at 2000 rpms, whereas if I'm accelerating along the interstate on-ramp I'll shift 1-2-3-4 and then lock the converter when I reach around 55 mph. You can shift from 3rd to 4th with the converter locked, that's pretty much what the PCM does altho it reportedly unlocks the converter for a split-second while it upshifts, I personally like to back the throttle off before I cancel the OD lockout to allow the trans to hit 4th gear, but then again I back the throttle off for every upshift as it's much easier on the clutches and at least in theory the trans should much longer. Then while descending hills I keep the converter locked and then the engine holds the truck back as I let off the throttle, I do this either in 3rd or 4th gear depending on the grade - general rule is to go down a hill in the same gear that you'd use to climb it, it seems to work pretty good for me.

The one thing I'd recommend against is just flooring the throttle while in OD with the converter locked, as this will force the trans to downshift under high line pressure and that makes for a quite serious jolt and I can't imagine that being any good for the driveline - the factory PCM shift logic involves unlcoking the converter and then downshifting but it happens really quick so most folks probably don't even feel it, so you gotta remember to unlock the converter before you mash on the throttle.