The issues with the 200's Aisin transmission

Compared to almost every other modern automatic transmission, the 200's Aisin AB60F transmission behaves very poorly in a number of areas.

With the torque converter unlocked, change points -except for the change to 5th gear- are generally too high in the rev range to take advantage of the twin-turbo diesel engine's flat torque curve. This means the engine revs far higher than it needs to, generating additional wear and consuming more fuel than required.

The 'sports shift' system doesn't work like any other light vehicle I have ever driven, only allowing you to restrict changes into taller gears rather than actually holding the gear selected. For example, if you select S5 then all it does is restrict the gearbox from changing into 6th. It does not hold 5th gear preventing a downchange to 4th. Again, this means you cannot even manually take advantage of the low-down torque of the engine.

But by far the most annoying 'feature' of the transmission is the operation of the torque converter (TC) lockup. The TC lockup function fully locks the engine to the gearbox, improving fuel economy and preventing heat buildup in the transmission fluid. The 'Cruiser's TC essentially only locks in 5th and 6th gears, at high speeds and under light throttle. By contrast, most modern automatics are programmed to engage the TC lockup as soon as possible and in as many gears as possible, particularly when operating in 'sports shift' mode. This is probably best illustrated by a table comparing the operation of the 'Cruiser's lockup with that of the ZF 6-speed transmission in my GT:

Coming up with a solution

The best way to fix the programming of the transmission would be to modify or replace the computer which controls the gearbox. This option is available for many transmissions around the World, but in the case of the 200 it's exceedingly difficult. While most vehicles have a dedicated Transmission Control Module (TCM), the 200's transmission is controlled directly by a combined engine/transmission ECU, and (at the time of writing) nobody has managed to successfully 'uncouple' the transmission control from the ECU. This means that it's currently impossible to customise the behaviour of the transmission, so you're pretty much stuck with the existing shift points and sports-mode operation. See remap update below.

What can be changed is the operation of the torque converter lockup, by overriding signals to the unit and sending phantom signals back to the ECU to prevent a check-engine warning. At the time of writing, there are three different companies manufacturing torque converter lockup systems for the 200:

One option is the European-made ECON*lock. Still the most automated option available, it's also the most expensive at about €1390 (A$2000). The manufacturer also claims it's the safest option, because it generates a pulse to operate the lockup valves, similar to the factory system.

Next up is the Wholesale Automatics manually-operated lockup switch. At a cost of about $600, it performs a lockup of the torque converter through manual operation of a dash switch, at any speed and in any gear between 2nd and 6th. Like the ECONlock, it uses a pulse to activate the lockup valves.

Then there's the system I've chosen, produced by Stefan at Richards Auto Electrical in South Australia. It's a speed-sensitive automated version, with the driver able to preset the speeds at which the TC will lock and unlock. The kit (which suits both the 200 and Lexus LX450d/570) is available direct or on eBay (where there are also bulk discounts). They also produce a manual system similar to Wholesale's switch, for around $300). Rather than the solid-state pulse used by the ECONlock and Wholesale systems, the Richards system uses a series of Bosch relays and a resistor to activate the lockup valves.

In my opinion, having the system automated to lock at a preset speed is by far the best option for a device like this. Its operation requires no input from the driver, so there's no need to constantly think about locking and unlocking it as you drive at different speeds. You maximise the fuel economy benefits of the system. I've also added a 3-way (on-off-auto) override switch, which allows me to revert to factory operation and also force lockup at lower speeds than I've preset, should the conditions require it.

Richards also produce a torque converter lockup kit for the Prado and Hilux.

Update June 2016: Several companies are now offering remaps or reprograms of the transmission control functions of the ECU. I have made several enquiries in an attempt to get full details of what parameters can be changed, and to what degree. However little information has been forthcoming. I will continue to investigate this option.

Update: Landcruiser 200 Transmission Remap

I knew Richards had been working on remaps for the auto for some years, but I wasn't convinced they had reached the level I'd be happy with. In April 2019, I got some feedback from another owner that made me revisit the idea. I gave Stefan a call to get the details on their latest version, and I liked what I heard. Chasing feedback, Stefan offered to come and remap my transmission at no cost when he was passing through a few weeks later, and I took him up on the offer.

The highlights of the remap are:

• Lower engagement speed for 6th gear: Now engages at around 92km/h in Drive, under light throttle.
• Higher throttle before kicking down from 6>5 and 5>4: The map ramps, so (for example) It drops into 6th at 92km/h if you are at <20% throttle. By the time you reach 100km/h, it needs ~50% throttle before it kicks back to 5th.
• Smoother gear changes: The remap applies torque reduction during gear changes. This makes a huge difference to gearshift quality, particularly when the lockup kit is active.
• Multiple maps: The remap has different settings for 'Drive', Drive+PWR', 'S' and 'S+PWR'.
• Allowing 5th and 6th gear to operate in low range: I didn't go with this option, but it's available if you want it, so you're no longer limited to 4th in low range.
• Elimination of MIL light: The remap extends the parameters required to generate the P2757 fault code, and stops the malfunction light sequence from appearing (although it still logs any fault code internally). The fault light can be a side effect of the TC lockup kits. I got this code perhaps once or twice a year, but haven't had it at all since the remap.

The verdict:

As I write this, I've now driven around 11000km since the remapping. That's roughly 1500km around town, 8500km (towing) on the Cape York trip and 2000km (not towing) to Melbourne and back.

I am absolutely rapt with the operation of the transmission since the remap. When you're not towing, it effortlessly drops into 6th gear at highway/freeway speeds and holds it even when climbing decent inclines. Between Sydney and Melbourne at 110km/h, it only dropped back to 5th on two occasions heading North, and once heading South. Even when towing (a 1.6T camper), it now comfortably holds 6th gear up moderate inclines. The vast majority of ~100km/h highway driving on the Cape trip was spent in 6th gear. Similarly, on the dirt sections at 80-90km/h, it easily holds 5th (locked at ~1500rpm) under almost all conditions.

Cruise control is now more usable, with better holding of gears reducing the hunting that was common on undulating roads. The reluctance to change back into 6th on the flat is now gone as well.

My only complaint to Stefan was that the slightly different settings in S6 (compared to Drive) sometimes caused it to jump straight from 6th to 4th when climbing a hill, but this has apparently been addressed in a later version of the remap, and in any case doesn't happen when in Drive.

At the time of writing, Richards were only offering the remap directly (rather than via their dealers), although this is apparently under review. If you go to their workshop in SA, they will reflash via the OBD port. Otherwise, if you remove your ECU, they will arrange for a courier to pick it up, take it to them where they will reflash it, then courier it back to you. You need to have a lockup kit (any brand) installed in order to have the remap done.

Pricing as at August 2019 is:

• • Lockup kit DIY install (inc delivery): $740
  • Lockup kit supplied and installed: $945
  • Lockup+Remap (DIY lockup install, courier pickup/return of ECU for remap): $1555
  • Lockup+Remap supplied and installed: $1745
  • Remap only (in-store, or courier pickup/return of ECU): $895*
    *Must already have a lockup kit installed (any brand)

Contact Richards Auto on (08) 8532-1411 for details/current pricing.