The transmission fluid lines run through the radiator I suppose to warm up the fluid faster which I can understand would be great in cold climates. But living in Phoenix that's just not an issue. Has anyone, living in the warmer climates, bypassed the radiator? Or is this just a bad idea.

 

the trans fluid runs in to the radiator to cool it down, not to warm it up. its called a transmission cooler for a reason.

 

Well, it depends what the relative temps actually are.

If the transmission fluid is hotter than the radiator (around 190-210 F), then the transmission fluid will be cooled down to a point no lower than the radiator.

If the transmission fluid is cooler than the radiator, the fluid will be warmed up to a maximum of the radiator's temperature. This is beneficial in cold weather conditions as the fluid must be warm enough for converter clutch lockup before the computer will engage the TC clutch. If the fluid remains too cold, TCC lockup will not take place and fuel economy cannot be maximized.

Running an external cooler by itself (without the radiator loop) is fine in most driving conditions. In Phoenix, you'll rarely, if ever, need to worry about it being too cold. In the event you do travel into or otherwise experience cold weather driving, you can simply cover some or all of the external cooler to keep it from cooling too much.

Steve

 

I was thinking of tapping in a bypass valve. That way, when in Phoenix, the radiator temps won't heat up the tranny fluid too much. Then when I go to Flagstaff where it's colder, I can open the valve and the radiator will warm up the fluid.

 

Installing a bypass around the radiator cooler will just net you a hotter transmission.

The radiator cooler is in the side of the transmission where the coolant has already been cooled. It is 20°F to 60°F degrees cooler than the thermostat temperature.

If you insist on removing the radiator cooler you will probably need a larger aux cooler to make up for the lost cooling.

 

you can by pass the radiator all together if you want providing you have a external tranny cooler installed

my merc
the wifes falcon
and the old F-250 plow truck
all have bypassed the rad cooler in favor of external coolers
never a problem
other than that i'm not getting involved

...zap!

 

I do have an external tranny cooler from the factory. It comes with the class 3 towing package along with the oil cooler. I just think that in this hot climate, tranny fluid passing through the radiator will get heated up too much after the engine gets hot. What I'm seeing here in Phoenix is when I get stuck in a traffic jam, and the temps are in the 100s, the tranny fluid really gets hot.(I have a tranny temp. gauge on the A-pillar) So I'm also putting a small 6'' e-fan on the tranny cooler for towing purposes. The bypass valve will allow me to switch back normal when I'm in colder climates like the high country.

 

There is something additional to consider.
The radiator will make the pan a higher 'average' temp.
You need to consider a deep alum pan as well. They are now less than $120.