Quote:
Originally Posted by maxfnz
- Auto transmissions usually have heat exchangers to the engine radiator (eg inside a header tank) for two reasons - faster warm up when cold (engine warms faster usually) and then to dump heat from the oil (cavitation heating of the oil in the torque convertor, friction). Any thermostat is usually just to stop the oil being over-cooled.
|
Thanks Max! This leads me to believe I'm not totally off base here. Though I have no doubt that the manual trans will have less gains from heating the fluid than an automatic trans.
Quote:
|
- Manual transmissions probably won't benefit from a heater siimply because of the oil viscosities ... most manuals specify a monoweight oil (80, 90) and if multiweight (80-90 or say 75-140) then it's going to get **thicker** as it heats, not thinner. Surely in that case you need cooling, not heating?
|
This isn't completely true. Lets use 75W-90 for example because that is what is called for by my transmission. As we all know, 75W90 oil acts like a 75W when cold, but 90W when hot. So lets pull the specs from the
amsoil site:
Kinematic Viscosity @ 100°C, cSt (ASTM D 445) = 13.9
Kinematic Viscosity @ 40°C, cst (ASTM D 445) = 87.6
As you can see, the 75W90 oil is still a lot thicker at 40C than it is at 100C. This is because oil thins out as it warms up, and 90W is thinner at 100C than 75W is at 40C.