I am wondering if there is a way to get my transmission to lock up in 2nd gear? I've done some research on this site and a few others and here is what one guy wrote:

"You have to pull the trans relay in your fuse box and jump the contacts so there is no more relay used. With that jumped, all it needs is a ground to activate the lock up. So you tap into the lock up wire on the PCM and run that wire to the toggle switch. Then run a ground wire to the toggle switch. When you turn the switch on you provide to ground for the system and the lock up is always on....untill you take to ground away. It sounds confusing but it's really simple. One jumper wire, one less relay, one toggle switch, one ground wire to toggle switch, and one wire from Torque converter lock up on pcm to toggle switch."

I was wondering if anyone else has tried this and how it works. The reason I want to do this is because there are times when I am towing and pulling a hard hill that the truck shifts down to 2nd. I have enough power to pull the hill in 2nd, butnot in3rd gear. I would prefer to have it lock up in 2nd gear in order to keep the tranny fluid cooler. I have a tranny guage and know the fluid temperature climbs quickly whenpulling even short hills in 2nd gear.

My concern with the description above is that if you pull the relay, the truck will never automatically lock the torque converter. Most of the time, I don't need the torque converter to lock in 2nd, but it's something I want to look into and have that option. Any opinions and experience would be appreciated.

 

Here are somesites I found a while back:
http://www.bouldermaskin.se/tips/tipsram.html

The top part is in German, but, if you scroll down the part about the tc mod is in English. This site has good diagrams.

This site:
http://www.4x4wire.com/dodge/tech/tc_lockup/

has small diagrams but offers a more in depth description. I never tried this, but I have read posts on multiple forums by people who did and had no problems. For anyone interested, you can also break the orange wire through a switch and disable tc lockup at will. This will get rid of the perceived "bog down" alot of people complain about at wot after shifting into third gear.

 

Here's another that's a little different, but supposed to work if you encounter a check engine light:
http://home.pacbell.net/jaybo/image2.gif

 

When my truck was stock the TC locked in third, unlocked when shifting into overdrive, then once in overdrive locked again. It never under any condition stayed locked while shifting into overdrive.
What if you put a switch on the TC and with it locked the trans shifts into another gear?
This is a timely post because I want to put a switch in my TC circuit so I can unlock it whenever I want.
Ok, here's my 2 cent, don't do what you want to do. Instead, put an auxillary trans cooler or better yet a fan cooled trans cooler.

 

When I thought about putting a switch to unlock my TC, Ithought aboutthe computer possibly settinga code because it was smart enough to detect that the program was calling for the TC to be locked but would sense there was no current flowing thru the circuit and set a code. Sure enough the computer was smarter than I was, I saw the P1765 in the code list. [:@] I have not had time to figure out the solution.
But thanks to mopower for the link to the solution![sm=thanx.gif][sm=happy046.gif]

 

Thanks for the info Mopowar. That's just what I was looking for. I have a two position lighted switch that I can use, rated for 20 Amp. The center terminal is labeled as the ACC, which the instructions say goes to the wire between the PCM and transmission. One of the end posts is for the power, the other is for the ground. Can this type of switch be used and will it light up? Also, does the ground wire that is to be attached to the switch go to the "Power" terminal or the "Ground" terminal?

I do have an aftermarket tranny cooler installed on the truck. It does a good job of keeping the temperatures down. I just want to experiment with this and see how it works on my truck. It's not often I would really need it, but a few times a year I do haul some heavy loads up in the 4 ton range on some pretty nasty back roads and would like the benefits of the lockup.

 

ASH,
just curious, whatis your trans temp towing that little trailer in your picture vs. the temp when towing the 4 ton load?

 

I've run as high as 210 on short, steep grades with the pop-up. Just a little higher when hauling 3 ton of coal on my dad's dump trailer. Of course the outside air temp was cooler when I was hauling the coal.

Also, this winter I got stuck behind a snow plow going up our local mountain. We went up about 25 mph, so my truck never shifted out of 2nd. The temp was at the bottom of the guage at the base of the mountain, so the fluid would have been no more than 100 degrees. When we reached the top, about 1 mile, it had climbed to close to 180 degrees if I remember right. 180 isn't high, but the change in temperature in that short distance is what concerned me.

Normally, my truck runs around 125 - 160 degrees in normal driving. It doesn't come up much more than that when towing on level ground or rolling hills where I can keep the speed above 50 mph and the tranny in 3rd gear. It's just when the torque converter isn't locked up, such as stop and go traffic and low speeds that I see the spike in temperature. Also, I've noticed that going from the stock thermostat to the 180 degree thermostat has helped to lower the normal driving temperature of my transmission fluid.

 

No problem. Just a couple of links in my favorites waiting to get used. You could possibly make the switch light up by putting 12v to the ground terminal on the switch since you will be putting ground where the 12v usually goes. If it were me I wouldn't risk it. Remember that if something in or on that switch shorts, you will be throwing 12v into the pcm's tc lock-up circuit. That would probably be bad news.

 

I've been reading up on this on some other sites that I found. It took a while to get through my thick head, but what I finally realized is that the switch completes the electrical circut by providing the ground for the clutch solenoid to engage the clutch and provide the lockup. So the wire that you are splicing into from the PCM is simply a ground wire and does not carry current. Therefore, I cannot provide current to the switch to make it light up. I think what I will dois get a small light and fuse, run a hot wire from the fuse box to the light, then splice the ground from the light into the wire from the switch. That way, when I flip the switch and complete the ground, the light will come on when TC locks up. I just like having the light as a reminder that I have the switch flipped on. Otherwise, I'll flip the switch on and mywife will start discussing some very important topicabout her mother [:-] and I'll forget that the transmission is locked.

WORD OF WARNING HERE. When you override the PCM with this switch, the transmission cannot downshift and it will not disengage. You can stall the motor or in the worst case, rear-end the guy in front of you in a panic stop. Read up on this in the links Mopowar provided.