Converter lock up help

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I have a 1991 FJ80 and it has a very annoying habit. When im getting up to hi-way speeds and hit 50mph the converter locks up. This is fine but when i hit a hill and start to accelerate the truck goes into 3rd rather than stay in 4th and un-lock the converter. This is also annoying when accelerating hard and it goes into 4th then 1 second later drop into lock-up. Is the converter lock-up electronic or is it mechanical inside the tranny? If it is electronic I want to put a switch on it so I can control when it goes in and out kind of like an overdrive button. If anyone has done this or has any info please let me know, thanks
 

Eicca

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Maybe we could stick an electronic valve in the lines that deliver the lock up "signal" for electronic control?

Don't listen to me, I really have no idea what I'm talking about.
 
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The A440F in '91 and '92 are fully hydraulic; no electronics. I'm pretty sure you can't do what you are dreaming of with our tranny's.

My Dodge tranny is hydraulic (Fully?, not sure) It is a 47RH. It still had a wire to clip and put a switch on for ground to control TC lockup. Like I said earlier, when that tc is locked (after 2nd gear) it is like going from a slipping clutch to a brand new one. SOB will roll!
 

Eicca

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I bet whatever it is that tells the TC you're going fast enough for it to lock can be hacked in some way.
 
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I haven't studied them and don't have the manual for the earlier trans, but from what little I have been told the are fully hydraulic. Controlled by a governor that is modulated by line pressure. One of the line pressure controls is the "kick down" cable that comes from the throttle body, so by adjusting the cable you can somewhat change the shift points.
 

Tapage

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"kick down" cable that comes from the throttle body, so by adjusting the cable you can somewhat change the shift points.

not sure if that will help with your lockup issue .. but at least giving it more play you will controll how much you need to push your gas pedal to allow the tranny downshift .. that means you can acelerate a bit more in the same shift before the tranny downshift ..
 
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TC lockup is controlled by speed, not throttle input IIRC. Mine will lock/unlock at 45 mph regardless of throttle position. Adjusting the kickdown cable will alter the shift points, but the TC lockup will remain the same.
 

Eicca

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TC lockup is controlled by speed, not throttle input IIRC. Mine will lock/unlock at 45 mph regardless of throttle position. Adjusting the kickdown cable will alter the shift points, but the TC lockup will remain the same.

Same. So somehow the hydraulics for the torque converter must be connected to either the RPMs of the transfer case or the speedometer system. I bet we could find a way to tap into this system if we knew where to look.
 
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Same. So somehow the hydraulics for the torque converter must be connected to either the RPMs of the transfer case or the speedometer system. I bet we could find a way to tap into this system if we knew where to look.

We've been over this with Rodney from Wholesale Automatics. The posts are on the Yahoo 3FE list.

IIRC, it's essentially controlled by a spring in the valve body, and the only option is at what speed it locks up. No active control, period.

Rodney does offer a modified valve body with 3rd gear torque converter lockup, but that's not what the OP is looking for, and again, no active control over lock/unlock.

Curtis
 
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Same. So somehow the hydraulics for the torque converter must be connected to either the RPMs of the transfer case or the speedometer system. I bet we could find a way to tap into this system if we knew where to look.

More:

The A440F doesn't "talk to" the transfer case, or the speedometer, or anything else. There is no "system" to tap into.
 

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