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2nd Trans Cooler

2189 Views 6 Replies 4 Participants Last post by  lapriester
Had the trans cooler/radiator issue last fall and did the cooler bypass. Now that it's getting warmer, I'm wanting to add a 2nd small external trans cooler to make up for the loss of the one in the radiator. What are your opinions on this? Is it really necessary (specially with the summer heat)? Is there a downside to installing it if it's not really needed? Thanks!
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Get a good stacked plate cooler that looks just like the stock auxiliary cooler. That cooler that's on there is a good one. Any one of these would do the job: Derale Cooling Products 8000 Series Fin and Plate Transmission Coolers - Probably the smaller one of the group would suffice as a replacement for the rad cooler. Honestly, the rad cooler is nothing but a tranny heater. It's the Aux cooler that does most all of the work as far as cooling. Think of it this much cooling can your radiator coolant running at over 200 degrees do for the transmission fluid. Since your transmission runs, under normal loading or on the highway, at 160 to 190 degrees (230 degrees can actually start oxidizing dyno fluid) how much "cooling" do you think rad coolant is giving you at over 200 degrees. Yup, that's cooling......the aux cooler is doing all the work.

If you have hard shifts longer on cold mornings because of the rad "cooler/heater" loss, next time you change fluid go full synthetic. Dyno fluid viscocity thickens in cold weather and thins as it warms. That's the cause of the harder shifts when the tranny is cold. Synthetic fluid viscosity is virtually constant cold or hot. If you change to synthetic you will notice the difference on the first cold start and wonder why it took you so long to switch to synthetic.

One point to bring out also. If you do a lot of towing close to MAX, on lots of grades, in hot weather or do a lot of hard off-roading with an auto tranny, you are just plain foolish if you don't have a tranny temp guage installed. Heat is the number one killer of auto trannies. You simply must know the temp when you put one to hard use.

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Just remember, when you are towing your rad coolant temp will be equal, for the most part to transmission temp. I don't know the exact temp of the thermostat in a Frontier but I suspect it will be somewhere close to 210*. In most towing situations, except those in high heat or difficult grades, your tranny temp will run 190-220* with approx 240 * being the level where fluid breakdown begins to occur. During those difficult situations your engine coolant temp will also rise to 220-230*. Logic and physics dictate that the rad cooler is completely ineffective in those situations. The only time the rad cooler may help at all is during rock crawling where flow to the air cooler is minimal unless the clutch fan is engaged (which it will be as rad coolant temps increases.

One more thought. If you have a serious concern, buy an auxiliary cooler with a thermostatically controlled fan. That type of cooler will so far exceed the original rad cooler it isn't worth discussing. One of those will cost you but it is also the most efficent type of cooling for any auto tranny. Your tranny will NEVER overheat with that type in use unless you have a serious failure that was coming anyway.

See here: Derale Cooling Products 12730 - Derale Cooling Products Dyno-Cool Remote Fluid Coolers - Overview - Then buy the applicable thermostat control.

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Uhhhhh, the Frontier is a Nissan vehicle, not a GM vehicle. Our Tstats open low, in the 170s and if you install a 350z Tstat, it is in the 160s.

I would suggest that the OP just run it as is and see if the temp gauge moves at all. I know I have been running mine bypassed in FL for a while now and have yet to have any issues. If you notice the gauge moving, then just add a fan to the OEM rad cooler and see where that gets you. If you need more, then upgrade the cooler.

Side Note: Just putting this out there, it may be worth checking out the cooler that is used on the Titan since it is rated to tow more then the Frontier, thus more heat/stress. If we use the same, then you should be good to go.
That's what I get for being a newbe. Thanks for that info. I didn't think any modern engine ran at that low a temp due to emission issues. CA trucks also run that low? That changes things some but I think under heavy load you could still see temps approaching 190*

If I bypass my rad cooler the truck will get a fanned cooler for certain since I plan to tow a boat with mine. My current issue is that I have an extended warranty I bought with the truck. If I bypass it will probably void any warranty on the tranny. Danged if you do and maybe danged if you don't. At least I know I'll get a new tranny under warranty if the rad cooler fails. Small consolation though. If it fails I'm sure it will be at the worst possible time.

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