your coolant and transmission temperature are related, as the atf is routed through your radiator to 'warm' it as likely as it is to 'cool' it.. so, when it's cold outside, the engines coolant actually warms up the atf... cold atf is hard on a transmission too, but 'cold' is only something under, i'd guess- 100* while actually working it decently hard..
high temperatures is what you want to avoid..
there is a thermostatically controlled valve in our transmissions that toggles @ 165*.. when it reaches that temp, it will open and close, sipping cooler fluid as needed to attempt to maintain it.. it can easily remain under 170* with an unloaded rig.. I'd guess 180* is about where it lives most often, and while operating unloaded at highway speeds in varying terrain...
as far as "while towing"... that depends on your load and your terrain... the ability to regulate temperature is governed by the volume of atf, the velocity and flow through the heat exchange, and the surface are of the heat exchange.. when that bad bear is pumping 100% of the atf 100% of the time out, and pulling atf back 'in' at near the same temperature it exited, well... you gotz a problem, yo..
the chart above is a good measure of what happens at various intervals.. if our rigs are healthy, and with the stock trans set-up and heat exchanges, there is no reason it shouldn't be able to maintain under 230#, even in the worst circumstances.. if it isn't, you're either running a rig with something wrong with it, or you're pulling/hauling WAY more than you should be for the demand you're putting on the engine.. (i.e. you're running WFO up a mountain pass w/ a lot of weight rather than at a reasonable speed- reasonable being within the systems ability to cool)..
anyway, hope this helps...
02-20-2013, 10:41 PM
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