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Lock up convertor mod


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Has anyone done the lock up converot mod here?

I've been told it's really easy and just requires cutting a wire running it though a relay and back to a switch on the dash. Is it really this easy or am I missing something?

Cheers Mick.

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There is more to it, perhaps because you want some sort of control and failsafe. So speed and brake related conditions need to be taken in to account as well as transmission temperature. I haven't done it personally as mine is manual but I'd wanted to have those safety overides for sure.

Have a look here - for an example how it is done Lock up converter manual switch

Here is another look at it courtesy of P4x4.com

Patrol auto converter lockup

Also a diagram from there FSschema.jpg

Ultimately it can be simple if you keep remembering that the switch is active, otherwise you'll have engine stalling.


Edited by Rumcajs
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I built this version using the above as a base, but did not fit the led shown near Pin3.

Basically you can't engage the lock until the vehicle is above 60kph, and even if the switch is on, ot will disengage below 55kph. This means you can't stop and stall the engine.

If you solw down below 55 and then accelerate gently back to cruising it will re-lock without too much thump, but it's not good if you accelerate heavily.

It's really good when cruising outback roads where you are on and off the throttle a lot at around 75-90kph - without the override the T/C locks and unlocks and becomes really bloody annoying.


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Speed sense is an excellent way for disengaging, especially on long trips when your brain goes into auto-pilot - if you have to stop for an eagle or brolga heading for your screen, you don't have time to disengage the manual switch, leading to stalling. That would be worse for the clutch IMO.

I found that in practise I usually flicked the switch to off after it disengaged, so the re-engag at 60ks didn't happen too often. Acceleration was non existent at 60 in 4th with the T/C locked.

Can't really say that it helped fuel economy, either. Best stage I got on the trip returned 11.5l/100, the worst was Oodna to Birdsville at 17.3l/100.

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Yes, you could put a switch between pin 30 and +12v, so that would completely override the speed switch and allow full lockup any time.

I plan to add this extra switch as well.

Maybe a pressure switch so it engages when completely off the throttle...

I guess the same could go with the brake peddle.. A switch to turn off the lock when you brake..

Just throwing a thought around

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If you need to lock at slow speeds, such as when descending steep tracks, the brake disconnect would be counter-intuitive; I can't say for sure, because I can't do it at the moment, but when descending in low low the engine would probably still provide insufficient braking to keep you crawling slowly, so the brake would still be required.

If following someone downhill or just being cautious, you'd get pisssed off with having to unlock every time you want to stop or ease over a ledge. I think the proper solution is reduction gears for this sort of stuff, doubly useful if you run 33" for off-road rather than standard 31" H/Ts.

Even better would be to run 4.6 diffs with 33" and then the T/C would lock up much better by itself. I run 32" highways, and even they bugger up the factory lockup due to the higher engine load being used by the ECU to decide when to lock.

Pity a set of 4.6s and reduction gears is around $2300 plus installation :(

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