AW4 coverter not locking

Both my brother and I have the same issue.
His xj: 89 145k 33"s 4.10 gears
Mine : 90 225k 33"s 4.10 gears

The torque converters do not lock up on their own.... I've added switches in both rigs to lock the coverter to aviod frying the trannies. I have not looked much into his rig but i've gone through all the sensors i can find on my rig and they all seem to check out fine. The trannies shift very well on their own... they just won't lock the converter. I've swapped in a known good TCU and same thing.

does anyone have any clues to solve this?? Is their something special the TCU needs to lock the converter? It seems that all conditions are already being met.

Thanks
Adam

My 90 has the same issue. Which wire did you tap into to manually lock the converter?

how do you know if you tc is locking up or not. im a little new at this stuff. i was interested in this b/c myjeeps tranny is acting really funny.

i have the same problem and no body seems to know how to fix it . Mine acts strangly shifting to 4th
How did you override the TC ?

ask brettm he seems to know his stuff when it comes these issues and aw4

brake pedal switch... there are 2 of them on a 90/older the lower/easier one to find is for the brake lights and if equiped cruise control. The upper one which has a vacuum line going to it probably is out of adjustment. I have found that the bracket holding it is flimsy and will bend back or sideways from time to time.

Yes, check the brake line input to the TCU, and also check the TC-lock output. Did you cut the wire, or just parallel your switch into the TCU output?

Skip

aduke said:

how do you know if you tc is locking up or not. im a little new at this stuff. i was interested in this b/c myjeeps tranny is acting really funny.

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X2

In 3rd or OD, you'll feel something like an upshift. Give it a little gas and watch the tach. If it revs up, no lock. If it doesn't move much, kinda in sync with ground speed, it's locked.

Did I really have to say this??

T&A-XJ said:

brake pedal switch... there are 2 of them on a 90/older the lower/easier one to find is for the brake lights and if equiped cruise control. The upper one which has a vacuum line going to it probably is out of adjustment. I have found that the bracket holding it is flimsy and will bend back or sideways from time to time.

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This is good info
I swaped out a 5sp truck to auto and was not aware of this!
I will have to get that "second switch" from the other truck

Thanks

Adam90xj said:

The torque converters do not lock up on their own.... I've added switches in both rigs to lock the coverter to aviod frying the trannies.
Adam

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Not having the TC go into lockup isn't a big deal, it will just decrease your fuel milage. It WON'T fry your tranny. Having it stuck in lockup or forgetting to unlock it after bypassing it WILL fry it.

Just a ditto on the brake pedal switch. I changed master cylinders once and the torque converter didn't lock up. When the switch was adjusted properly the toque converter locked up perfectly.

cLAYH said:

Not having the TC go into lockup isn't a big deal, it will just decrease your fuel milage. It WON'T fry your tranny. Having it stuck in lockup or forgetting to unlock it after bypassing it WILL fry it.

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I disagree, most all of the tranny heat is generated by torque converter slip. When the converter locks up, no heat is being generated by the converter.

RobertF said:

I disagree, most all of the tranny heat is generated by torque converter slip. When the converter locks up, no heat is being generated by the converter.

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x2,

I have a trans fluid temp guage and when the TC starts to slip temp climbs extremely fast.

karim_gabra said:

i have the same problem and no body seems to know how to fix it . Mine acts strangly shifting to 4th
How did you override the TC ?

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check your neutral safety switch nss do a search

Yes but he only time your TC locks up is when you are in a low load/cruise situation. As soon as you even begin to pull a small rise it unlocks and starts to give you extra torque to maintain speed. This is the half shift you feel when on the highway. Many cars prior to 1990 didn't even have lockup TCs. Very few before 1985 had them. Its a gas savings feature and is not meant to be subjected to heavy torque. With your TC lockup disabled your tranny is just like any other 1970s era tranny. Happily slipping away eating at your fuel milage. Excess TC slip causes(like a stall test or pulling too heavy of a load) will produce excess heat. When you are pulling a heavy load up a hill or are crawling up nasty trail, your TC is unlocked and the lockup portion of the TC has no effect on anything. Driving with the TC disabled will not damage your tranny, as a few have stated here they have driven for quite some time without it. I myself did not hook up my brake pedal swt when I did the conversion from the Peugot to AW4. That was 2 years ago. Heck my 92 Dodge Diesel tow rig doesn't even have a lockup TC.