Aux Transmission Cooler

[Billy "Poserlander" Badly]

I'll be picking up a small cargo trailer soon (dry weight 700lbs, likely never exceed 2000lbs loaded), and in my internet searching to learn more about towing (something I've never done), I keep coming across rec's to add aux tranny coolers and/or fans. I drive a 2011 Xterra S, w/ a tow limit of 5000lbs.

Is that extra cooler truly necessary? Wouldn't be super expensive, and if it saves my transmission in the long run, great, but I also don't want to waste time and effort if it's unnecessary.

Thoughts?

 

[Downs]

Never hurts to have a trans cooler even if you aren't towing anything. A cool transmission is a happy transmission. I don't tow heavy things but still hvae one in my Jeep along with a gauge.

 

[Dilldog]

Won't hurt, but the biggest thing to watch for is constant torque converter lock and unlock ( will be a change of about 200rpm) and down shifting and upshifting a lot. Thing to do when either of those happen is to manually select a lower gear. More likely than not you'll see this when trying to get into overdrive and pulling hills at highway speeds. The more stuff a trans does the more heat it builds. Also keeping it serviced and make sure the oil you use has the specs will keep it happy and cool.

 

[smritte]

Everything they said and add on a remote temp gauge. You want your trans temp under 185 if possible. My Cruiser runs around 170 hwy and 185 towing. On my TJ I had an oversized cooler in a custom radiator, a big remote under driver side with a fan on it and I couldn't get it under 195 until I added another on the front. Anything over 300 spells quick death. I was running in the 280's towing up hills. Took the 3 coolers to bring it down.
I've towed my whole life and never saw those temps. Its an issue with the TJ's.

You can add in a temp sensor into the side of the trans pan and if you want to see what your cooler is doing, add one into the return line to your trans. Your better coolers will give you an estimate on temp drop. My remote rear was rated at 45 degree drop. Total drop for me was about 110 degrees out of the 3. My cruiser never gets hot running the factory cooler.
I prefer Derale Coolers, specifically their stacked plate or plate and fin.

 

[reaver]

Installing a secondary trans cooler is never a bad idea. I run a Hayden 678 in my 04 colorado. I'm not towing anything really, but loaded with gear and crawling around at low speeds, I rarely see Temps go above 190. I run it in series with the stock cooler. Line come goes from the return portion the radiator, to the aux cooler, and then back to the trans.

 

[M Rose]

I'll be picking up a small cargo trailer soon (dry weight 700lbs, likely never exceed 2000lbs loaded), and in my internet searching to learn more about towing (something I've never done), I keep coming across rec's to add aux tranny coolers and/or fans. I drive a 2011 Xterra S, w/ a tow limit of 5000lbs.

Is that extra cooler truly necessary? Wouldn't be super expensive, and if it saves my transmission in the long run, great, but I also don't want to waste time and effort if it's unnecessary.

Thoughts?

I always recommend an auxiliary transmission cooler, unless the vehicle came stock with a heavy duty cooling system. The stock coolers are generally under designed and heat is the number 2 cause of automatic transmission failure. Number 1 is lack of maintenance. Do transmission maintenance when required by the owners manual, and get a cooler and your transmission problems will essentially go to zero.

 

[Billy "Poserlander" Badly]

Thanks all, seems pretty definitive. Temp sensor and aux cooler in series with the stock one sounds like the way to go.

 

[Dilldog]

I will say it is possible to over cool as well. Most modern transmissions are designed to run between 185 and 220. I always shoot for between 190 and 210. Anything under 185 and you wont be able to get an accurate fluid level when checking. Also never bypass the oil to coolant cooler, transmissions need heat to work properly, and being exposed to engine coolant in the cooler helps the trans come up to temp faster.
Also it's worth saying, with any oil if you see a temp at or above 250, change it as soon as possible. That's when things start breaking down big time.

 

[Charles_Alarie]

Xterras come with a tranny cooler from the factory. I tow about 900 lbs regularly and only see temps rise in long slow steep climbs. I use a scan gauge to monitor tranny pan temp and torque converter temp. Works well.

 

[Billy "Poserlander" Badly]

Xterras come with a tranny cooler from the factory. I tow about 900 lbs regularly and only see temps rise in long slow steep climbs. I use a scan gauge to monitor tranny pan temp and torque converter temp. Works well.

Thanks, good to hear from someone with a similar use case. I was aware that it had one, but seems like everyone recommends an aux one as well, connected in series with the existing one. At least, that's what I found on many of the Xterra specific forums. Do you have the Scanguage II? I read that it didn't originally have the ability to monitor trans temps (like the more expensive Bullydog), but that firmware updates have corrected that issue. Getting one of those may be my first step... Do you disable OD when towing?

 

[smritte]

Thanks, good to hear from someone with a similar use case. I was aware that it had one, but seems like everyone recommends an aux one as well, connected in series with the existing one. At least, that's what I found on many of the Xterra specific forums.

Having a factory cooler will save you money. As @Charles_Alarie mentioned, if you can read trans temps with a Scangauge, that will save you money too. You really only need a second one if your factory one cant keep up with the heat. Toyota put a big external cooler on mine as well as the one in the radiator. I didn't have to buy anything other than a way to watch the temp.

 

[Charles_Alarie]

Xterras come with a tranny cooler from the factory. I tow about 900 lbs regularly and only see temps rise in long slow steep climbs. I use a scan gauge to monitor tranny pan temp and torque converter temp. Works well.

I have a Scanguage 2. I believe it has trouble reading trans temps for older 2nd gen Xterra but post 2010 or so on have no issues. The light on my scanguage does flicker at times which is a known issue that can be remedied by the firmware update. On fairly level highway towing I do not disengage OD but do when I am offroad or climbing at slower speed in the mountains. Sometimes I have to manually select gears to avoid heat but have never had any real issues. I think you just have to watch your temps and slow down when needed. My trailer is fairly light so that definitely helps with engine and trans temps.