Understood, here's your revised wiring setup:

1) cut the purple/yellow wire, extend both ends so they reach the dash (you already have that).

2) you need a 3-post switch, also known as a SPDT switch, but watch out as those come in the "on-off-on" version or the "on-off" version - you want the "on-off", basically one that has no middle position of it, something like this really: SPDT Heavy-Duty Switch - RadioShack.com

3) disconnect both wires from your existing switch and toss it away. Take the now-loose end of the purple/yellow wire that goes to the PCM and connect this to the middle terminal of your new switch.

4) take the now-loose end of the purple/yellow wire that comes from the transmission and connect it to one of the end terminals of your new switch. Watch out for the on/off labeling of the switch, as you may know when a toggle points at "on" it really connects the middle terminal to the one that sits under the "off" position of the toggle, and therefore when the toggle is set to "off" it connects the middle terminal to the one that sits under the "on" label. So really, connect that wire to the end terminal that sits under the "off" label of the toggle switch.

5) find a suitable position in the fuse panel that gets 12V power only when the ignition is on, tap into that using an ATO add-a-fuse breakout thingie, and then connect it to the end terminal of the switch that sits under "on" label of the toggle, but install a 22k-ohm resistor between them.

What that does:
a) switch set to "off" - current flows from the fuse panel, through the add-a-fuse, through the 22k resistor, through the SPDT switch, through the purple/yellow wire, and into the PCM - PCM is happy cause it gets proper volatege, but converter lockup stays disengaged.
b) switch set to "on" - current flows from the TCC solenoid, through the purple/yellow wire, through the SPDT switch, then through the other end of the purple/yellow wire, and into the PCM - basically you're connecting the two ends of the purple/yellow wire directly, thus restoring PCM control over the lockup, which is your normal factory mode.
Basically the purple/yellow wire leading to the PCM is always on the receiving end of both circuits, and you're only switching the inputs between the real TCC lockup solenoid (when switch is set to "on"), and the "ghost" one you created with the add-a-fuse and the resistor (when the switch is set to "off").

 

Man that is an awesome write up. Thank you very much. I am going to go to the Shack in the morning for the resistor and switch. This site should be proud to have folks like you who supply such great tech.

 

Lol, it's no big deal man, good luck with the wiring. Just a tip - as a power for the switch I used the fuse for the tank selector valve, but put a voltmeter on both terminals in there to make sure which is the supply and which is the load side - the wire coming out of the add-a-fuse thing should be on the load side.

 

thanks for the tip. I am going to do this asap.

 

can locking the torque converter in first or second gear provide a good means for getting engine braking when going downhill under a heavy load (20-25 mph pulling 8-10 ton hay loads). Or will that fry something bad.

 

Well, my understanding is that in 1st and 2nd there is not enough pressure to keep the converter from slipping, and with the small friction area the factory converter has that leads to a burned up lockup clutch and eventually code #62 and all the PCM joys associated with it. If you have a big tripple or 4-disc converter then you can try it and it will likely survive it just fine, but on a factory unit no way.

Actually, I'd recommend against engine braking with such heavy loads - not so much cause of the transmission, but because of the rear end - the way those things are designed when you engine brake with something heavy pushing you what happens is the ring gear grabs on the pinion and tries to pull it backwards towards the diff carrier, sometimes that force is a bit too high for the crush sleeve to handle and that deforms and the pinion ends up being loose, leading to premature gear wear and eventually structural failure.

 

I was able to get mine to lockup in second gear, but that was above 2000 RPM and I have a 3 clutch lockup. I'm not sure I understand how pressure would be any lower in 1st or 2nd gear. Engine RPM affects that, not line vehicle speed, unless there is an aspect that I am not aware of. Can't say I've heard of engine braking problems like you describe either, but I'm not an expert.

 

David, that's just what I was wondering myself - line pressure is related to the pump speed, which is driven by the engine, if the engine still turns at the same speed converter should be able to lock and hold... Beats me man, that was the only explanation I've ever been given.

The engine braking issue with the rear axle was something discussed on OBN, pretty sure it was RLDSL or one of the other heavy haulers who had first-hand experience with it.

 

whats OBN? this is my first OBS PSD and Im always looking for more forum sites because I dont belong to enough of them already. (Insert sarcastic smiley here)

 

OBN = oilburners.net, which is another diesel site that many of us here frequent. I personally am a member at FTE, OBN, and TDS, last one is pretty slow but the first two can keep me busy reading all day long How's that wiring project coming along?

 

I got the resistor from a friend. I looked at my local Vatozone for the switch but Im gonna have to ride 30 miles to a radio shack. I plan on that in the morning. I did get the inline fuse though.So I will let you know. Im looking at a DP chip and gauges as my next mod.

 

What the heck is a DP chip? We have all mechanical injection, we don't use any chips whatsoever to manage the engines. Another place to look for a switch is Lowe's or Home Depot or any other hardware store.

 

change it.

 

oops! I got a PSD. but the mod for the e4od would be the same. I didnt realize what area this was in!

 

+1

Change the fluid and filter. Don't bother with additives, at least not yet. If you really want to try one you can put some in at anytime later on.

The myth that changing the fluid in an auto transmisison can somehow cause problems doesn't really apply to relatively modern transmissions like the E4OD.

Flushing can however cause problems in some cases.