I have a 1998 Discovery, 3.9l V8. I do a lot of very heavy duty towing, I tow 3,500kg triple axle mobile dental clinic caravans to rural schools in some very remote and ruggered areas of New Zealand.

I have fitted an electronic temperature sensor to monitor the automatic transmission oil temperature. It is mounted right next to the existing transmission temperature sensor, part number AMR 4948. Typically when driving unloaded (i.e. not towing) the transmission oil temperature is showing around 65-75*celsius.

However I would like to know what is the trigger point of the factory fitted AMR 9498 sensor so I can tell on the digital meter when things are starting to get dangerously hot. The markings on the AMR 9498 are: F135C 941-2.

Thanks,

Terry

 

I guess no one on here knows? Maybe you can call the dealer? Or find out who makes the sensor and call that company and ask for specs on it?

 

would call a tranny shop and see what they would consider to be a normal operating temp. I would also do more frequent fluid changes or even switch to a synthetic ATF for better operation and lower temp. readings.

 

Thanks guys,

I have searched Google, no luck. I will try a couple of transmission shops, although I suspect their answers will be more a guess and theory rather than exact.

Based on the digital gauge I have fitted over the last week the 'normal' (not towing) range seems around 80*c, so it may well be that 135c stamped on the sensor stands for 135*c. If I had a spare switch I could immerse it in hot water to see when it triggers. Although to get water to 135*c you not only have to heat it, but pressurise it as well..

Mike... I am very interested in the synthetic ATF option. When I have it serviced (every 10,000kms by a LR Dealer) I have the engine oil replaced with the instructions to use the best oil available, and to replace the gearbox, diff and transfer case oil every 20,000kms. This might seem excessive but the consequences (and costs) of a gearbox problem pulling a caravan up a hill on the East Coast are way too scary to take risks. My best recovery costs from the nearest tow company (100miles away) are over $1,500US.... Not to mention my commercial losses...

The last invoice shows they used Castrol Magnatec 10w/40 for the engine and a combination of castrol gearlube and standard ATF fluid for the transmission, diff and transfer-box.... They also used 2 bottles of Morleys Oil Stabiliser, which I suspect they added to both the engine and gearbox.

Does this sound good enough, or if you can suggest a much better synthetic option, then by all means I'll take it...

Thanks for your input... much appreciated...

Terry

 

If you are really wanting a rating for the switch, put it in boiling water with an ohm meter hooked to it and test the water it is in. Probably can't get the water that hot, but it might get close... Should give you an idea. But my educated guess is 135 if it is stamped on it...

 

Thanks for that, could anyone advise the best synthetic engine and transmission oils to use...?

 

I use Royal Purple, but then again, I sell it too....

Mobile 1 puts out a good oil as well..

 

I don't mind if you sell it... as ultimately I want the best and will pay accordingly. Obvioulsy I'm in NZ so I guess I will buy local thou.

Can you suggest a particular Royal Purple product..? Such as a trade name, gear lube etc so I can track it down in NZ.

Thanks...

 

I only sell in mass quantities, like to trucking companies. I can only sell to mass transport and industrial. I can't really sell like automotive retail. That's a different market.. Not sure about the availability of our products outside of the US. RP makes something for everything in any weight needed. Motor oil, ATF, PS fluid, even an additive for the coolant called Purple Ice. It is all under the Royal Purple Name, though. If you can't find it, Mobile has good synthetic products, and lots of people like Amsoil..

www.royalpurple.com should point you to a dealer, along with the full line of products and specs you might need.