Pro's and Con's of transmission cooler
 

I have a 2012 mazda 3 hatch with the 2.5L in it, 5-speed automatic. I live in Texas so its usually pretty hot. I was told to change my transmission fluid now (just hit 50k, the manual says nothing about when to change) and to the change it every 30k miles. I was also told I should get an external transmision fluid cooler. I see I can get them for rather cheep. I was wondering the pros and cons of them, and suggestions on which to get for under/around $50?

we also live in texas, and we have a 2013 mazda3. it is a lease, so i aint doing squat to it. however, we do have several other vehicles that have automatic transmissions. the first thing i would recommend is lubegard:

International Lubricants Inc. (ILI) - Makers of LUBEGARD

the basic stuff has been around for years. several manufacturers used to have service bulletins to have this additive put in their cars. volvo, gm, jaguar, slaab, to name a few. even tho your car probably now uses synthetic fluid, lubegard is cheap(around 10 bucks at oreilly's, autozone, etc) insurance. the second thing is that i would recommend you change the fluid regularly. i change our other cars yearly. i have a 2002 outback, and i use it to deliver the mail, which is really tough on transmissions. i have both a transmission cooler, and a power steering cooler. there are 2 types, tube and fin, and bar and plate. bar and plate is much more efficient than tube and fin, and, of course, it is also more expensive. i also installed a 7" spal pusher fan in front of the cooler, and wired it to come on with the radiator fans. the subaru has 140k. most important is that you should regularly check your fluid level, and condition. i use a mityvac fluid extractor to get the trans fluid out:

Great deal on MityVac 7201 at ToolTopia.com

i also use this to change my oil, crawling under that sucker and no good jack points is a pain in the butt. the extractor makes it easy. i cant wait to return this pos when the lease is up. we also have 2 99 millenias, and both do not have external trans coolers. but i service them yearly, and i always add lubegard. both cars have superchargers, so they can be hard on the transmissions. they do eat up axles, but so far the transmissions have held up.

Be careful, cheapest isn't always best. Potential for poor fittings, poor construction & leaks.