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Asking for a friend (auto box overheating)

steverjuk

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Message I got @Fattrucker, he’s currently in the arse end of nowhere in Scotland, so spotty mobile coverage, so posting for him.


Hi I have a '92 K Landcruiser 80 series automatic. Japanese import with 315,000km on the clock . The truck "has been very well looked after by a mechanic" so I was told . It has ran fine for two weeks or so like a truck with a quarter of the mileage . "All the service items(oils/fluids/filters) were changed less than 100miles before I bought it. Again I was told this by the previous owner .
I'm new to the Landcruiser scene and I'm having issues with the auto-box overheating .
The truck is kitted out for overlanding with roof tent , awning and internal storage system . So I would say it's "fully loaded" . Having said that I would have thought the truck could cope with vastly more weight than we have on board without issue ?
Having used it briefly on a mild off-road byway last weekend the "A/T OIL TEMP" red light came on . I pulled up and let it cool off for 15 minutes . Started back up and had no issues for the rest of the day .
Now driving up long motorway hills at 55-60mph the same red "A/T OIL TEMP" light comes on and goes off a few seconds later on the downhill side (almost rolling down the other side barely touching the throttle) .
The idle seems to fluctuate too much too . From 600 rpm(ish) in park to something over 950rpm (a hair under 1000rpm) . It holds a set number of revs for roughly 30seconds . Then drops a few hundred rpm for 30seconds then back up again . But never the same rpms (900 , 750 , 825 , 600 , 950 you get the picture) basically the idle is "hunting" putting it in "drive" brings the revs down considerably (550rpm ish) from where it likes to sit (up nearer 950rpm) . The "idle up" control knob is pushed all the way in and seems to operate as expected . (It will lock and hold revs as though the accelerator is being pressed . Which is how I'm lead to believe it should operate . And doesn't appear "sticky" in any way ) .
Could these two issues be connected /related please ?
 

Michael Montgomery

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Hi idle can be adjusted on the fuel pump. Sounds like this is not running right but nothing to do with the overheating of the transmission.
You didn’t state if it’s a petrol or diesel?
Also has the radiator been changed?
 

steverjuk

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Sorry it’s diesel, don’t know about the state of the radiator. I’ve got him checking at fluid levels tomorrow at the moment it’s chucking it down.
 

fbnss

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not that this is any help but mines "fully loaded" and i've had the light on twice in my ownership, once booting it up some switchbacks in Slovenia and once on the transfagarrasan where i was enjoying it a bit too much. Ie on steep twisty roads where its changing constantly. It's never had a problem booting it on the motorway or just chugging along, so.... it's not right
 

Michael80

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Hi,
I have had the same thing happen due to the torque converter lock up solenoid not working, do you have the overdrive button on the gear selector?
 

Michael Montgomery

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Hi idle can be adjusted on the fuel pump. Sounds like this is not running right but nothing to do with the overheating of the transmission.
You didn’t state if it’s a petrol or diesel?
Also has the radiator been changed?

Reason I asked was that I changed some years ago my radiator for a aftermarket one and later found out on hill / mountain climbs the A/F Temp light coming on. Upon investigation it appeared the radiator bottom section that cools the transmission was not sufficient. You wouldn’t know that upon daily driving unless you had a separate temp guage for the transmission. This I got and to resolve this added a OEM radiator behind the front grill and now it all resolved.

I did drop down the transmission and change out the torque converter but later realized it was the radiator.
 
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Lorin

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A/T OIL TEMP light comes on at 150 degrees and goes off again at 120 degrees. Once it has come on you have fried your AT fluid and need to do a full change (not just a pan change). Fried fluid will be much more prone to overheating. The A442 auto box is notorious for overheating. The OEM transmission cooler is in the bottom of the radiator. Contrary to uninformed opinion it is a very well built and effective cooler, it just isn’t up to the job of managing the A442 once you are carrying weight and/or running bigger tyres. First thing to check is that the radiator is clear of any gunk as it will accumulate at the bottom and impair the trans cooler. A good flush of the system may be in order and is easily done. Also ensure the cooler system, particularly the fan is working as it should, and that the radiator is in generally good order and not blocked with mud etc.

The single best option is to fit the largest possible transmission cooler you can, downstream of the OEM cooler. This will have a huge effect on keeping temps low. It is also recommended to switch to fully synthetic ATF as I can handle higher temps better. Castrol Transmax Z is recommended by Wholesale autos in Oz, otherwise a good fully synthetic ATF. Fitting an ATF temp gauge is a also a good idea as it helps to manage the temps.

As others have mentioned it is worth checking that the torque converter is locking up. Given it’s a 92 and an import, he’ll need to check if the box is the full hydraulic or the electronic.
 
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