gearbox oil
- Thread starter billycan
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Manufacturers spec' is the heavier oil. The recommended spec' is 80W-90, but the thinking is to use 75 :thumb2
Mine's filled with 80 at the moment, but I'll be changing it out for 75 before Winter, for sure
glanrichbex
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- Apr 15, 2012
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It depends where you are using the vehicle, for colder climates there is a requirement for thinner oil to compensate for viscocity. It's also not good to go too thin either.
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Thicker oil is not good for your gearbox.
it's not heat from the engine, it is heat generated by the friction of the moving components within. The oil plays a very important part as well as lubrication, it is a medium which removes and distributes heat from the moving parts to the outer case. Alot of the moving parts are not actually running in the oil but rely on splash caused by the movement of various sections of the geartrain. Thicker oil does not splash very well, especially in cold weather.
Bearing races have poor oil retention so the fact the oil is thin means the heat is removed sufficiently by a small flow to keep that bearing running within specification.
If the oil is thicker than specified - it means the oil is more viscous and so not moving as quickly through the bearing, this causes more heat build up, you may even be starving it of oil and so increased wear. If a bearing gets excessively hot the tempering on the surfaces of the race and rollers can be lost and will become soft, this will cause bearing failure.
:thumb2
Interesting observations there.
The Land Rover LT77 box was designed to run with ATF Dextron 2, that is significantly thinner than the majority of lubricants used in transmissions.
Maybe they had a lot of excess heat to disperse?
Probably...........it'll have been the standard Landrover half-inch tolerances that caused it
