I want to put a trans cooler on to aid my TH400 but am not sure which to route to first. Should I run the line through the radiator first or the aftermarket cooler? I don't want to reheat the fluid by passing it back through the radiator if that is what will happen. Thx for any input, JC66.

I bypass the radiator altogether on my setup. I also mount the cooler so there is a good 2" plus between the rad. and cooler.

I also bypass the rediator. I'm not one of those that believes that you're actually heating the tranny fluid, because tranny fluid usually runs hotter than engine temperature anyway, so there must be some cool down effect from running it through the radiator. Water temp in the radiator is usally a few degrees cooler than inicated on the guage because that reading is at the motor. The reason I bypass it is because the radiator "cooler" is nothing more than a heat transfer tube. Doesn't run through the radiator, just down the tank. No sense in running it through there if you have a dedicated 3 or 4 pass tranny cooler. However if you still want to run it inline w/ the radiator, run it through the radiator first(for an intial slight temp. drop), then through the cooler.

Hi JC,
Using a cooler is an absolute necessity
for hipo use. I must DISAGREE with not routing your line through your rad as well.
If you live in a hot climate then the tranny fluid will be much hotter than coolant
temp. Running thruogh the coolant will drop the temp. of the fluid enabling your cooler to work even better.
On the other hand, if you live in a cool
climate, or even have cool nights, not running through the rad may cool the fluid too much affecting it's viscosity (like making it thicker). This can put tremendous stress on
transmission seals leading to premature
failure. If you run it through the rad as well, however it will warm up the fluid for you,perhaps preventing a seal problem.
Hope this helps,
Ron D.

JC66,

To answer your question, Run the outlet line from the tranny through your radiator, then to the auxiliary cooler.