Should I install a torque converter on my old Mitsubishi 4WD?

QUESTION

Hi John,

I have searched your website but can’t find anything about torque converter lock up kits. I enjoy the channel very much and respect your honest insights, would really like your opinion on these. I have an inkling that they may well be in the same grouping as catch cans and alike.

We currently own a 2011 Mitsubishi Challenger XLS auto, and tow a 1.8T caravan and the reason for the interest in the first place is that the Challenger does not like to make a firm decision about which gear it would like to be in when towing anywhere in the 80 to 100km/h range, thus causing the rev range to fluctuate wildly.

We rarely move along at 100k, we tend to stay in the 80 to 90 range to cut down on resistance, improve economy and because I would like to get to our chosen destination safely.

These kits, depending on which one I look at, seem to promise that the auto will be able to maintain revs lower than previous, thus putting less strain on the engine, and will enable the transmission to engage and stay in the correct selected gear. This all sounds ‘too good to be true’.

Look forward to hearing your thoughts, good or bad as they may be, at least they will be honest and informed.

Thanks,

Rob.

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ANSWER

Rob,

So, you have a 10yo Challenger, which has been doing the job just fine for you for a decade. (Not perfectly, but it’s doing the job fine.) They’re a bit agricultural, but fundamentally sorted and reliable.

Apparently, you’ve taken a recent interest in torque converter lock-up kit pornography. And it looks so enticing that you’re considering giving it a crack. (I’m just summarising the current state of affairs, objectively.)

In my view, it’s time for you to start thinking like an engineer, and not like an aftermarket powertrain porn downloader. (Hey, you asked for my opinion - what were you thinking?)

Hunting in gears is a product of the powertrain’s operational software control (programming). I don’t see how a locked-up torque converter will alter that.

If a torque converter is unlocked, there is a little slip between the engine and the transmission. This consumes energy, but it also reduces harshness and shock loading in the powertrain. This ‘strain on the engine’ claim is bullshit. Like, what ‘strain’ on the engine? It’s not pumping out anything like peak torque or power towing your van at 90km/h on the highway. So that’s absurd.

(Pro tip: peak power and peak torque only occur at wide-open throttle. So, if you’re not mashing your foot to the firewall, the engine’s not approaching either, and it is therefore doing only light work. It’s relatively un-strained already, towing on the highway. So, why cure a problem that does not exist?)
There might be a slight fuel economy benefit from fitting a kit like that, but that would be offset against the price of doing it, and the potential reliability implications, and any other negative operational feedback (harshness, etc.).

Essentially I wouldn’t ‘eff’ around aimlessly at great expense with something that appears to be serving you well.

Seriously - the manufacturers of all this crap tell anyone who’ll listen it’s twice as tasty as chocolate, but it also prevents tooth decay.

You, however, are not required to believe all their marketing bullshit.

In closing I would suggest a bunch of engineers at MMC designed the Challenger pretty well - to deliver robust performance reliably, albeit with less refinement than a Merc. You’ve proven this hypothesis for a decade, operationally. Why dick with it now?

How about, instead, experiment with knocking it out of overdrive when towing and seeing if the hunting improves?

Sincerely,

John Cadogan

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