99 Cherokee, How do I lock up the torque converter?

Hi everyone, I have been reading alot of postings here on , and I am getting alot of information that is conflicting, as well as more info then I need.

Here is the deal, I hope some one out there can help me out. I would like to be able to lock up the torque converter on my 99 cherokee, that is all I want to do. I don't need to manually shift all gears, or override the 1-2 gear selection on my shifter. When I drive on the highway, I would like to beable to lock up the transmission to get better mpg.

I was told last time I was out on the trails, that it was only one wire to cut and add a switch to... Does anyone know what wire this is and where it is located?

Can anyone help me out? The more detail in the answer the better. Pictures would be nice too...

Thanks for any help!

Should be yellow power one side switch
White/black on other should be solenoid 3
Read this
Showes all wires on TCU
http://www.transonline.com/transdigest/magazines/1997-10/Shift%20Pointers/index.html
Also go to my name and click on posts started where I did manual shifting

Got bored so here you go
http://naxja.org/forum/showthread.php?t=1065702

So, I just splice into the yellow and black/white wire? That seams like it would create a direct short?

:dunno:


The torque convertor already goes into lock up when cruising down the highway. What are you trying to gain?

I would "T" tap off each wire you send 12V to solenoid 3 it locks up that is all solenoid 3 does is controls TC lockup
you are pulling power from the yellow and sending power to black/white when you flip switch on

And he is correct it already locks up

I went on a jeep trail crawl in Washington state. I rode went with a friend of a friend. He had a switch on his dash, when we were riding on the highway, he would flip the switch up and the rpm dropped. When I asked about it, he told me that I only had to cut one wire, but he wouldn't tell me what one. I would like to have the same mod on my jeep. I guess I don't know if he was pulling my leg or if it really was only one wire that he had to cut. At any rate, I see all these write ups about how to control all shifting, make your aw4 drive like a manual shift postings, I just want to start out small. I guess if it can't be done, then it can't be done. I just wish that tom would have told me what he did! :banghead:

I'll give the yellow tap and black/white wire tap a shot this weekend...

All you need is to feed the wire for solenoid C 12 volts. However on a 99 you are going to get a CEL as a result. I believe you would be able to avoid a CEL by cutting the wire instead of tapping it, and using this circuit:


I cannot guarantee that it will not trip a CEL but it is much less likely to. The 6 pin part is a DPDT toggle switch of your choice, wire it up like that and toggling the switch up will lock the torque converter while toggling it down will leave the stock behavior functional. The only way I can think of that a CEL would be triggered with that circuit is if you turned the override on while the TC was already locked, and didn't flip the switch fast enough.

I believe raneil managed to mostly eliminate his CEL with 1000 ohm resistors but I'm not sure, and can't find the thread in my bookmarks list right now - 100 ohm will definitely do it but they can't be found as easily at radio shack.

Everyone else is also correct, if you do this you won't really gain much unless your TPS, brake switch, or TCU is screwed up and for some reason your TCU is never locking the torque converter by itself. The stock torque converter lockup map in 3rd/OD is something that I've always thought was pretty close to ideal.

For the curious - circuit above works like this: with the switch in the down position, the wire from the TCU is routed directly to the solenoid via the small jumper wire across the top two terminals. With the switch in the up position, the TCU wire is routed to a dummy load resistor to ground and the solenoid is routed to a +12V source (which should be ignition-switched power to avoid draining the battery if you leave the vehicle parked with the override on for a long period of time by accident.)

I would think if you just taped it it would think the tcu it was doing it but would backfeed
Might cause cel I did it on a 95 and 96 I knew for sure it wouldnt cause one on those years
Just try its just a wire lol

BTW I read you can get rid of CEL with 50 on off cycles dont know if its permant or not though no experience with 97+ obd2

outracing said:

I went on a jeep trail crawl in Washington state. I rode went with a friend of a friend. He had a switch on his dash, when we were riding on the highway, he would flip the switch up and the rpm dropped. :

Click to expand...

Yours already does this automatically. If it doesn't, something is broken (the circuit for the brake switch, probably).

It will lock up in third or fourth, only in the gear you are selected (so in "OD" it will not lock up if its in third, for example) and I believe above 1800 rpm's.

Get cruising on the highway. Gently and very briefly tap your brakes. When you see your RPM's jump about 500, that was your torque converter unlocking. If it is not doing this, find and fix the problem instead of working around it.

So on a 2000 it looks like I have 3 or 4 white and black wires going into my TCU how do I know what one to tap into for the lockup switch?

I agree not much gained if the system is currently working correctly. However if tgeres a ability to modify the valve body to lock first and second basically manual shifting this would be nice going slow.

I used to have a tourge converter lock switch on the 47re behind my cummins but it was mostly useless since it already locks 3rd and 4th on its own.

Being able to lock 2nd requires mods inside the valve along with the lock switch. I now just drive it.

With the switch locked the truck no longer downshifts on its own and damage can be done because it can now stall in the gear its locked in. A brake switch to unlock lock switch would have been nice.

Allowing upshifts with switch locked can also cause harsh stacked shift were its shifts from second to 3rd locked then 3rd locked to 4th locked.
The imput shaft could then be at risk.

A healthy tranny with alittle boost in pressure from a shift kit without a lock switch would be ideal. One that when you push the throttle it goes and when on the brakes it slows


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