I do a few things with my test car. Yes, my Impala SS has become my test car for towing applications and such, and mainly a car I just tinker with for kicks. I put an secondary in-line cooler, installed a deep pan trans cover (added 3 or 4 quarts more) and moved to synthetic trans fluid by Amsoil. When I did tow the Safari I rarely saw 200 degrees towing up a significant grade.
In the winter time, the synthetic does perform better at cold temps and, I place cardboard in front of the radiator, since it can get below zero in these parts.
The test car goes trans routing goes from the trans to the radiator, then to the external coolers, then back to the trans. I placed a 160 degree thermostat in the car and the car in the dead of winter gets to about 175 degrees (more than enough to get into closed loop) and still provide some heat the tranny in the winter, though my trans temp gauge in winter does not come up off it's base temp of 150 ever, in winter.
I will say the the trans cooler in the cop car like Impala seems a bit better than the thin small cooler added to the truck line (I have an '04 3/4 ton Burb). I have been considering getting one of those B & M supercoolers, but don't want to heavily modify the trans cooling lines to do it, and I also don't want to use the rubber hoses, braided with stainless weave or not. The issue as I see it is that the coolers have NPT connectors and I think the factory lines are AN. I haven't looked too far into it, but I do want to upgrade the cooler at some point. Putting a more than adequate cooler in (with syn trans fluid) should do the trick in towing and in winter, similar to that of what the test car indicated.
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