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Anyone do the torque converter lock mod?

I have just put a 1993 4,0 with AW4 from a ZJ into my '86 XJ. So far the only problem (apart from the rear diff I smashed today) is that the lockup never locks up. I have suspected the transmission comfort/sport switch, which I do not have and don't have a diagram for, I've also suspected the cruise control thing which I threw out. But here I got a hint about the brake switch, maybe this is what's causing the problems? Is it so that the converter will never lock up if it doesn't get a signal from the brake light switch, which I haven't connected to the engine harness, thinking it only had to do with the cruise control?
 
it'll stall if you stop with it in lockup

I've got a writeup in the tech section of steve88xj.com--- my way uses no diodes however--- and I haven't had one problem
 
seymouj said:
I just read the write-up on that link and have a couple questions.

First, it seems the goal there is to manually force second but we want to stay in first right (for compression braking)?

If that is true, couldn't we just cut the line to solenoid 2 and run it through a switch - off would be first gear only, on would be normal operation and no need for a diode?

Someone please tell me if I have this all wrong!
Click to expand...

Yeah, that will work... BUT do you want to intercept the computer's signal output? That may cause problems. this is how it works:

Your shifter position is REALLY 1,3,4; its the TCU that controls the shifting. If you take your TCU OUT, then you'll have 1,3, and 4. The idea behind my way, is to turn off the computer, and have the 1,3, and 4 shifting positions, and have a switch to solenoid 2, to put it in 2nd.

If you put in a switch for solenoid 2, and use that without turning off the TCU... well I don't know what would happen--- I THINK though that maybe the TCU will want to put it in 3rd and turn the other solenoid on? Wonder what would happen there?

Seems to me like you wouldn't want to be messing with the signal with the TCU on... when you're intercepting anything. The lockup switch is different though, because you're simply giving power to the source that the TCU will give power to---- and when it goes to give that solenoid power--- its simply already there and the TCU is none the wiser


am I being too confusing? I think I'm starting to confuse myself! :anon:
 
flexj said:
This sounds like the next best thing to a full manual valve body. Is there a link or write up somewhere that gives more details? I've thought about locking out the tc but only for driving hills in 3rd and 4th on the highway. I've never thought about it for an offroad application. The 2nd gear thing, is that to get 2nd at a lower speed and totally bypass 1st? What do I do, what do I do? I like this idea.
Click to expand...

I use my 2d gear switch alot off road. To me it offers a better range of between-obstacle speeds w/o the overrev of 1st. I suppose one could start off in 2nd for slippery conditions (snowy road, slick mud) I haven't tried that yet.

With my 89 AW4/231 in low range, in 1-2 the tranny stays in first (maybe it'd upshift way up in the rpm band...it never has for me) if I put it in 3 or OD, it'll shift 1-2-3 very quickly...and 3 isn't too handy...so the tranny hunts & pecks around. I used to just leave it in 1st and creep along, but 2nd seems just 'better' for the mild stuff...

I don't lock my TC off road other than descending hills in low gear.

On road I use it a lot in 3rd & OD...I think that the switch that controls 1-2 also allows control of 3-4 when in the higher gears. I didn't play with this feature much yet, but forcing a 4>3 downshift w/o accelerating or shifting the lever might be handy on the highway :dunno: I have been doing the 4>3>4 drill using the lever, and the TC stays locked throughout. The only time I unlock the TC on the road is when coming to a stop or sharp turn where 3rd gear is too fast.

www.bigoffroad.com has a good tech writeup with wiring diagram. I got my diodes @ radio shack...IIRC they were 500vdc, 15 amp? approx 3" long overall, 1/8"D x 3/8"L body, $5.00 for 4
 
Follow up / correction: the silicon diodes I used are Radio Shack # 276-1114: 1kV, 2.5A, Three per package.

I used two "push-pull" switches on the front of the console cubby (on either side of the handbrake handle) so I don't have to fumble around for them in the dark or take eyes off the road/trail. I generally drive with my right elbow on the cubby lid, and this is the most convenient place for my tastes.

My rig doesn't have the power mirror control there, and I had to drill a (1/2"?) hole through the trim and inner liner for each switch. I ran the wires between the console body and the black trim along the R/S beside the shifter,

L/S switch is the TC lockup (pull out for lock) R/S switch is to trigger a shift solenoid (pull out to lock in 2nd gear) slapping both in returns the tranny to 'normal' automatic function.

As I mentioned above...while cruising up the road in OD...the R/S shift switch will downshift from OD to 3rd when pulled out. I think I'll get to like this feature, as I always had been shifting 4-3-4 with the lever.
 
I also did a writup many moons ago. It was on Jeepin.com, but I don't know if it can be found there any more. I believe the files (at least the important ones) can be found on the madxj yahoogroups site under files and then perhaps under Jeff's Jeep Mods. Basically, I put a switch into the brake line to the TCU to simulate the brake being depressed. This action causes the Torque Convertor to unlock which can be useful on gradual hills while on the highway. It allows the engine to gain some revs without downshifting all the way to third. The other switch and diodes will force the tranny into second gear without backfeeding power into the TCU when the switch is providing power to the second gear solenoid. This makes rolling along the trail in second gear possible without the tranny wanting to shift to third or first. I pulled power off the line that is only powered when the shifter is in the 1/2 position so that if the 2nd gear switch is left on, it's function is disabled when the shifter is in 3 or D. Hope somebody has found this useful. BTW, I did this on my '92 and I now have a '98. I haven't done anything on the '98, but I hear putting a switch in will cause the engine management comp. to register a fault. The truck will then not shift or run correctly. I may do a little investigation in to this sometime though, as I liked the switches. Jeff
 
RCP Phx said:
Has anyone figured out how to do this on the the newer trans???
Click to expand...
I'm wondering the same thing. Is there an option for those of us with newer XJs?
 
I've read both way of doing this. Seems simple enough. Is one way better than the other. I guess the diode way is less likely to cause problems. Steve, do you have any feedback into you TCU with out diodes? What would the feedback do or cause the TCU to do? I'm doing this before the weekend so I can try it out. Rock on.
 
Jeff, do you have any more info on that? My converter won't lock up, I have a transplanted engine (and AW-4) from a 93 ZJ into my 86 XJ, and I don't know anything about that brake swith or where it should be connected, except I know which pin it is to enter the computer through. Any more information would be great! (Not sure I need the brake switch, I just need to hook it up so my lockup will lock up (automatically))!
 
Did I understand the write up correctly. I believe one of the links said that he recomended turning off the ignition to the jeep before fliping the switch to lock up the torque converter. How could you ever use the lock up switch then because you couldn't restart you engine if the torque converter is locked wouldn't it be like trying to start an engine with a manual tranny and not pushing in the clutch? So can you or cant you lock up the torque converter "on the fly"?:confused:
 
I did it tonight. I didn't notice the TCC locking up when I turned the switch on. The engine didn't stall when I came to a stop. Will it only do that in low? Other wise it went smooth.
 
Woody, anyone, please help!

Sorry to resurect the old thread but I finally got the time to do this mod. I followed the write-up on the big-off-road site but I'm having concerns. I dont see that its necessary to wire up the switch to kill all the power to the TCU if you never want to run the tranny in a full manual set-up. It seems to me that you would just need the 2nd gear switch and to be in the 1-2 position with the shifter to get the power to both selonoids allowing 2nd gear. If I am right then I should have 2nd gear and the ability to lock up the TC with what I have done but it doesn't seem to be doing anything when I flip either switch. Am I on the right path? :confused:
 
I spoke to a 'leading' tranmission repairer ( the states auto club's opinion ) about fitting a switch for the lockup converter. He did not recommend it at all as had done many auto re-builds because of it. He explained that the converter was only designed to be driven from the engine side of it and if you manually lock it, it gets driven by the tranmission side. This leads to over heating very quickly causing failure. Now this was on a Nissian Patrol that a kit was avaliable for at the time but I take it the principle would still be the same?
I know with other autos the torque converter lockup releases as soon as you lift off the throttle to prevent heat build up and give you better economy but some are saying here this is not the case with the AW4? Are you sure?
Anyone had any long term problems with using it?
 
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