[ASturSubaru01]

Hi everyone,

I just purchased a new-to-me '08 Outback 2.5i Limited, approx. 78k miles, 4 speed "EAT" with overdrive. We're thinking of adding a trailer hitch, as we very occasionally rent a light trailer to move items from place to place. Nothing super heavy, like 1500 pounds gross weight including the trailer.

In keeping with that I'm looking at trailer hitches and transmission coolers. I notice the 2.5i doesn't seem to have a cooler standard. Do you think it's a good idea to put a transmission cooler on this car, regardless of whether much towing will be done?

They cost less than $100 and I cannot imagine it *hurting* the car in any way. You can't "overcool" transmission fluid, but if you put the cooler in the wrong place I can see detracting from the rest of the car's cooling capacity.

I ask because my Dodge Intrepid 2.7l with more than 200k miles came stock with a trans. cooler. I recently did some maintenance and took out some trans. fluid from that car, and the cooler is clearly doing its job - the fluid was in pretty good shape even after almost 100,000 miles (last time I saw it) and the car still drives and shifts very well.

So what do you think? Is adding the trans. cooler a decent preventative maintenance strategy if the car can expect to see a lot of miles? (Ours can).

 

[AWDFTW]

I think it is a safe investment for any vehicle that will see towing duty. There is a write up in our DIY forum.

 

[StuntmanMike]

I think it is a safe investment for any vehicle that will see towing duty. There is a write up in our DIY forum.

I agree! It can't do anything but help.

 

[ASturSubaru01]

Thanks, folks. I agree and I'm going to put one in/on.

 

[John E Davies]

You can't "overcool" transmission fluid

Sure you can! If you don't let the fluid reach full operating temperature in the colder months, you can have moisture/ condensation issues. You do NOT want your tranny fluid to be running hot all the time, but warm is good..... and cold is bad.

I suggest that you install an external cooler inline with your OEM cooler, to keep temps stable, or bypass the OEM cooler entirely and also install one of these:

Derale Cooling Products 13011 - Derale Performance Fluid Control Thermostats - Overview - SummitRacing.com

The big advantage of the "bypass the OEM cooler" setup is that it eliminates any possibility of coolant mixing with the ATF.

John Davies
Spokane WA USA

 

[Seabass]

put it inline with the oem one, before the radiator and use a thermostat to keep from overcooling.i've monitored my temps with the cooler being after the radiator with no thermostat and with normal driving, it never went over 130f. thats not hot enough. im considering removing the cooler or getting a thermostat.

 

[ASturSubaru01]

Thanks to everyone and food for thought, that's for sure. I still want to add it and the trailer hitch but I want to do it the right way. I really like the car as you can tell from my post earlier this evening, and I want to do everything I can to keep it running *well* into six figures.

A thermostat sounds like a good idea to plumb in. My goal here is to enhance the reliability of the transmission for a reasonable price, knowing that I will occasionally tow a trailer with about 1500 pounds gross weight, without costing an arm and a leg and without detracting from anything.

 

[Bimmer]

That's good to know...

I keep thinking about an additional transmission cooler, but I keep putting it off. Now my sense of urgency is gone.

Having to figure out plumbing in a thermostat is even more daunting than removing the '08/09 grille!

 

[Seabass]

You don't need it at all for regular duty. I only got mine because of my crazy cross country towing trip. I haven't needed it since. I need it even less since I switched to the wrx radiator. My overall temps are lower than before. I think it's time to test out the built in cooler by itself.

 

[Euchre]

I suggest that you install an external cooler inline with your OEM cooler, to keep temps stable...

This. Aftermarket cooler first, then into the OEM one in the radiator.

Most manufacturers now will tell you this, because you want a stable temperature in the transmission. The radiator helps you achieve that, and keeps it fairly well in step with the big thermal mass the transmission is connected to - the engine.

 

[subiesailor]

You only need it if your hauling 1500+lbs in 100+ degree temps and a long steep climb. I happen to know someone who cooked their 4eat at 180,000 miles towing a 1700lb 21ft boat in 105 degree temps the climb is Fresno ca to Huntington Lake basically going from about 800ft to 8000ft in about 20 miles in 100+temps. Doing that run in my 5spd non turbo 2.5 two guys two duffel bags flat out 4500rpm 3rd gear on the wicked climb we topped out at 50mph. Same car towing a 600lb boat we did 30-35mph on that climb. I highly doubt you need a cooler and yes the stock set up has a cooler.

 

[Bimmer]

You only need it if your hauling 1500+lbs in 100+ degree temps and a long steep climb...

I highly doubt you need a cooler and yes the stock set up has a cooler.

Just to be clear, the 2.5 engine may not make enough power to cook the tranny in regular driving, but the XT engine definitely does.

In August we drove from Sacramento back to Humboldt County, and driving up the coastal range it was over 100° F and the coolant temp spiked to 110° C (230ish F). I don't have an ATF temp gauge, but I can't imagine the ATF was much cooler. This was with only two adults and a small child in the car, and a trunk full of normal luggage (nothing especially heavy).
Of course we had the AC running, and I wasn't driving slow, but still...

I've seen the same thing happen in similar circumstances: hot day, long uphill, AC running, temp needle rising. Wow!

Seabass, tell me about installing a WRX radiator, please!

 

[Eul_Suby]

Seabass, tell me about installing a WRX radiator, please!

\
^^^+1
I'm thinking of getting an oil cooler but I might just save up for a WRX radiator if they work a lot better than my stock one without having to put in an oil cooler.

 

[normalabby]

Sorry for dredging up an old topic, but I wanted to pick your brains. I'm hoping to move this winter, back to the NW from South Dakota. I have no idea what kind of load weight I'll be towing, and I won't know till I get to packing everything! Obviously I'll keep it under the recommended.

It's going to be quite cold, more than likely, but I do have some big passes to drive over. 2005 Outback XT. Should I get a cooler installed? Does near freezing temps negate the need?

 

[traildogck]

You know, I don't tow anything with my XT. I did just upgrade the radiator and did an external AT cooler...due to my high power build.

When I scrapped the oem rad...I broke off the top and bottom composite tanks. The lower houses the trans cooler. It is about 14"x1/2"x1/2" sandwich flow plate. I honestly am surprised it does anything at all. But I honestly don't know what the car needs for cooling.

I was just surprised how small it was. The flow rate can't be very much either.

 

[Brucey]

I added a transmission cooler on the 2000. I then towed with it, played tug of war against a Chevy dually with it, drug a Miata up a vertical cliff with it, and pulled multiple oak trees out of the ground with it.

The transmission never slipped, the engine gave up the ghost before the transmission did.

That transmission is now in a dune buggy and doesn't have any issues there as far as I know.

I don't know if the cooler was a factor for the long life it had. But it certainly didn't hurt.

 

[rasterman]

You know, I don't tow anything with my XT. I did just upgrade the radiator and did an external AT cooler...due to my high power build.

When I scrapped the oem rad...I broke off the top and bottom composite tanks. The lower houses the trans cooler. It is about 14"x1/2"x1/2" sandwich flow plate. I honestly am surprised it does anything at all. But I honestly don't know what the car needs for cooling.

I was just surprised how small it was. The flow rate can't be very much either.

Yeah, but consider that it is an oil-to-water heat exchanger. Both fluids have similar density, both stay in liquid phase, so you get a ridiculous amount of heat transfer from a relatively small physical package.

When you need to move the heat from something dense (oil, water, etc) and dump it into air or gas, you need way more surface area to get any efficiency. So an oil-to-air cooler will be huge when compared with the same rated oil-to-water cooler.

 

[t1r2u3s4t]

rasterman has brain!

 

[InTheBay]

Is there any current info on using the engine cooling system to cool the trans fluid? Or would a seperate rad/reservoir/pump be needed.

 

[subiesailor]

Hi everyone,

I just purchased a new-to-me '08 Outback 2.5i Limited, approx. 78k miles, 4 speed "EAT" with overdrive. We're thinking of adding a trailer hitch, as we very occasionally rent a light trailer to move items from place to place. Nothing super heavy, like 1500 pounds gross weight including the trailer.

In keeping with that I'm looking at trailer hitches and transmission coolers. I notice the 2.5i doesn't seem to have a cooler standard. Do you think it's a good idea to put a transmission cooler on this car, regardless of whether much towing will be done?

They cost less than $100 and I cannot imagine it *hurting* the car in any way. You can't "overcool" transmission fluid, but if you put the cooler in the wrong place I can see detracting from the rest of the car's cooling capacity.

I ask because my Dodge Intrepid 2.7l with more than 200k miles came stock with a trans. cooler. I recently did some maintenance and took out some trans. fluid from that car, and the cooler is clearly doing its job - the fluid was in pretty good shape even after almost 100,000 miles (last time I saw it) and the car still drives and shifts very well.

So what do you think? Is adding the trans. cooler a decent preventative maintenance strategy if the car can expect to see a lot of miles? (Ours can).

For your use no. I live in Hot california if I werevtowing 1500+lbs over the sierras in 90+ temps multiple times a yr I would look into a added cooler. Your car has a stock cooler the ATF passes through an exchanger at the oil filter. It does two things, warms the ATF and also cools it.