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Discussion Starter #1
Car: 2013 Premium Outback 2.5i CVT, current mileage 21,560 plus.

Where: 30 miles West of Las Vegas going up a long hill.
Speed: 61 mph set in cruise control.
Temperature outside: 82 degrees Farenheit

Pulling: 1500 lb. trailer that I have pulled since years 2006 w/previous 2006 MT Outback.

Problem: Automatic Transmission (AT) warning light goes on requiring me to find a place to pull off and there were none for about 1/2 mile in high speed uphill dense freeway traffic.

Pulled off and after about 5 minutes with the car idling the AT light goes off. Continue trip another 450 miles going up other steeper hills at higher speeds and higher temperatures (70mph and 87+ degrees) and no AT light goes off again.

This was very disconcerting and dangerous given the amount of high speed traffic and how low a trailer weight the OB was pulling. Another thing which immediately followed was after our stopping and getting back on the freeway was that the passenger seat's airbag shut off even though my wife was in the seat. This occurred at high speed and required pulling off once again, turning the car off and on to rectify the problem. This is the second occurrence of this issue.

I have been extremely satisfied with my car till now and wonder if this will occur again, was a fluke, perhaps a bad relay with the AT or what. This is my second 1500 mile plus trip with the car in hot weather towing the trailer. The first was uneventful. In any case, it required me to either stop or not in a dangerous situation. Had I been on a two lane mountain road with a big drop with no pull offs, I would have either had to ignore the AT and keep going or stop in the middle of the road.

Finally, the weather was not really that hot and I am in the Southwest quite a number of times during the year when the Las Vegas and Arizona temperatures hover at 105 degrees plus.

Does this mean that these CVT transmissions are going to be incapable of towing lightweight trailers up hills in these temperatures? I am afraid this may be the case and hoping that it is not. My 2006 MT never had a problem with my small popup trailer other than when starting out on inclines (had to slip the clutch sometimes) and then never did actually wear out the clutch.

Any feedback appreciated.
 

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2009 Tribeca Now - 2004 Outback EJ259 - Sold
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I bet the AT fluid temp is reaching too high a temperature.
You might look into an aftermarket transmission cooler placed inline the AT cooler circuit after exiting the radiator.
Really any AT transmission could benefit from one if regularly used to tow in these conditions.
 

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Discussion Starter #3
As far as I know there is not a way to put a transmission cooler on the cvt units as they are sealed units. If there is a way it would be great. However, if the tranny overheats in such a mild situation yhen it means SOA should throw out their 2700 towing limit or say if only works in the winter, or sell a tranny cooler such as I used have on my Pilot or Surburban.
 

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Every transmission has a cooler even a cvt. Just need to get with a Subaru dealership or a good subaru mechanic to figure out a better solution.
 

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2011 Outback Limited. White, Sunroof, 2.5, CVT. Bought 2/15/11. Love it! Broke 109K, 2/20.
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I'd get to the dealer and bring up the issues. There might be a gremlin running around in your Subie. Since the seat belt light and the AT light seem to be acting in a sort of unison I'd suspect an electrical problem.

Have you towed this trailer before or was this the first time?
 

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Don't use cruise going uphill.
 

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2011 Outback 2.5i Premium, CVT, Steel Silver, all-weather package. Upgrades: Tweeter kit, BlueConnect, media hub, remote start, Curt 2" receiver hitch.
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There is a lower tow limit when going up long hills in hot weather. It is in the manual. I believe it is 1,250 pounds or so.
 

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2013 Outback 2.5 premium, NON pzev!
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80-90f is warm but.... When towing with an automatic higher engine rpm's provide better transmission cooling. The Outback is not exactly a "tow" vehicle but probably will do better with manual (paddle shift) to 5th in this situation to provide better transmission fluid cooling through the trans. cooler. In my F-350 drw when carrying or towing a heavy load (has a trans. temp. guage) higher engine rpm's result in lower transmission temps. We obviously have no trans. temp gauge other than the overheat light in our o.b.'s. Downshift or go to manual and ease up a bit. 1500# up a long grade takes a lot of power, plus this is a little 4 banger that is meant to move the car not that and tow up a fricken hill/mtn. BTW: Elevation/altitude will also have a bearing on available h.p. that can be produced in a normally aspirated (non-turbocharged) engine, i.e. higher =less hp that can be produced!
Of course all that does not explain the air bag issue....don't you just love all the fancy smancy computer crap on cars these day's???? One blip here and a whole bunch a other blips show up for now apparent reason. :gasp::gasp:
 

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Wait, why would higher RPMs provide better cooling? after about 2000rpm you'll get the same flow rates through both water & ATF pumps, and the fans on outbacks are electric.

Now, I could see the higher RPMs of a lower gear equivalency producing somewhat less heat from the trans even though you are producing more heat from the engine - same fuel burn, more friction. Not like these cars have crank-driven fans.

...at the end of the day safe towing includes being able to handle any interstate grade at 40mph but if you want to go faster, bring more to the table or expect poorer results.

I'm still in overall agreement with patchelect that there may be an electrical issue at play.
 

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80-90f is warm but.... When towing with an automatic higher engine rpm's provide better transmission cooling. The Outback is not exactly a "tow" vehicle but probably will do better with manual (paddle shift) to 5th in this situation to provide better transmission fluid cooling through the trans. cooler. In my F-350 drw when carrying or towing a heavy load (has a trans. temp. guage) higher engine rpm's result in lower transmission temps. We obviously have no trans. temp gauge other than the overheat light in our o.b.'s. Downshift or go to manual and ease up a bit. 1500# up a long grade takes a lot of power, plus this is a little 4 banger that is meant to move the car not that and tow up a fricken hill/mtn. BTW: Elevation/altitude will also have a bearing on available h.p. that can be produced in a normally aspirated (non-turbocharged) engine, i.e. higher =less hp that can be produced!
Of course all that does not explain the air bag issue....don't you just love all the fancy smancy computer crap on cars these day's???? One blip here and a whole bunch a other blips show up for now apparent reason. :gasp::gasp:
+1 I haven't towed that much weight yet, but have noticed that on an upgrade with speed control engaged that the tach is fluctuating up and down a bit. This is the computer adjusting the CVT ratio up and down trying to maintain the best economy possible but also adjusting for the increased load. I have to believe this minor "hunting" or shifting the CVT ratio generates some heat in the transmission. When I'm towing my boat (1200#) on the freeway this summer I plan to go to manual mode 5th on the CVT to let the engine rev a little higher, stop the ratio fluctuations on the CVT, and hopefully keep both the engine and transmission a little cooler. Even on my V8 pick-up I lock out the overdrive whenever I'm towing more than 1000 lbs, and my Subie is just a 4 banger, so it just seems to make sense.
 

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Wait, why would higher RPMs provide better cooling? after about 2000rpm you'll get the same flow rates through both water & ATF pumps, and the fans on outbacks are electric.

Now, I could see the higher RPMs of a lower gear equivalency producing somewhat less heat from the trans even though you are producing more heat from the engine - same fuel burn, more friction. Not like these cars have crank-driven fans.

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I am not sure how the transmission fluid is cooled on the OB, but on my truck it is cooled with a by a oil/transmission fluid heat exchanger so the water pump rate doesn't matter as long as the engine temps stay in range and the oil flow rate/temp stay in range. Big rig trucks running up hill are @ lower gear/higher rpm's for same reason. Maybe I'm not explaining well or am off the mark on this. I certainly agree that I would take it in for a computer read and??? I just don't think these little 4banger's are meant to tow at or near limit's without a need to adjust operating procedures.
 

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There is a lower tow limit when going up long hills in hot weather. It is in the manual. I believe it is 1,250 pounds or so.


Ok so heres the scoop. CVT and AT. Both have cooling related limitations. CVT 1350lbs in 104+ temps abd long climbs. 5spd AT 1500lbs. Things that lower that rating box trailers and head winds and towing at high speed. MT do not have cooling issues in the same sense. Even the mt car will be pushing cooling limits in hot temps and 1500lbs steep climbs and high speeds.

Curious what rpms you were running on the climbs. I have towed enough in 80+ temps with a few good climbs never had a temp warning.

BTW little hint cvt cooling and engine cooling are tied together. Kick the heater on run the fan on high to shed some extra heat. Dont run over 3300 3400 rpm at the top end during the long climbs and you should be much better off.

#1 You will all ways run out of cooling before you run out of power when towing and decent climbs.
 

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Oh and yes the cvt has a cooling system. Sealed simply means no maint till 100k in non towing use. Doesn't mean the cvt lacks cooling for its fluid.
 

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I am not sure how the transmission fluid is cooled on the OB,.
Talked to Subaru tech. mgr. this morning. He said the cvt IS cooled by a heat exchanger that is part of the radiator cooling system! I stand corrected. He went on to say however that when in full auto the cvt & computer is trying for best fuel efficiency (which most of us know), that said he recommended the following: down shift with paddle manually, slow up a bit and not use cruise control when going up grades or towing. Also re-iterated the limited towing capacity of a 4 cyl. He recommended having the fluid checked and probably changed if an overheat has occurred. They check the color. Hope this helps. :D:D
 

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Shadetree -- with any AT CVT or other wise when your facing a long climb where temps could pose a challenge its always more efficient to manually pick a gear lock that gear down and simply do your climb based on RPM with your speed being more or less your secondary concern. This is what truckers do by the way. Any time AT's hunt or change gears during a long climb and towing they generate added heat. Not to mention its annoying to have an AT changing things up on you when you found the happy rpm and are just plugging along up the hill.

For those long climbs where you know that running temps with the AT are a very real possible problem. Your goal is to choose a gear that lets you run in an RPM range where you getting into the upper torque band of the power yet you want to keep to the lower end of those RPM's to keep heat generation on the exhaust and engine side of the program under control. RPM's are your friend till your generating far more heat and friction than whats needed to get the job done. The Flat 4 in the subaru is pretty cool regarding its flat torque curve. When grinding over a long climb running the car at 3200rpms is more or less giving you nearly as much pulling grunt as you get at 4000 yes you might be going a little faster but 4000rpm is generating way more exhaust heat and friction with the engine than 3200 is and your speed pending your climb and load maybe only 10mph faster if that.

Thats where you lock into a gear pick an RPM that lets you cruise along in the slow lane doing what 50-45mph if your trailer load and climb is really that steep and you just let the car do its thing. No temp issues and your car survives the trip. Even my 4.7L V8 has made some trips where a 1800lb trailer 110 degree heat had us doing 45mph up a 19 mile climb to 8000ft starting at just 850ft. We wanted AC on to stay comfy and doing 45-50mph up the climb was no big deal. I could have done 70mph but for sure the AC would have been off and we would have been cooking some expensive parts.

The Subaru CVT works great in AT mode but on those long hot climbs pick a gear 3rd - find the 3200rpm mark and plug along if you can carry 4th at 3200 then the speed bonus is great. Jump it to 3500-4000 for a speed boost to get around slow traffic if needed etc. But I found our CVT and 2.5 will grind along all day long at 3200rpm without heating things up on the really tough climbs. I've been down to 2nd at 3200rpm a few times it gets slow but hey if you wanted a fast tow you would have bought a F350 Diesel which would have towed that trailer at 90mph with the AC blasting with no indication of anything getting hot.
 

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Shadetree -- with any AT CVT or other wise when your facing a long climb where temps could pose a challenge its always more efficient to manually pick a gear lock that gear down and simply do your climb based on RPM with your speed being more or less your secondary concern. This is what truckers do by the way. Any time AT's hunt or change gears during a long climb and towing they generate added heat. Not to mention its annoying to have an AT changing things up on you when you found the happy rpm and are just plugging along up the hill.

For those long climbs where you know that running temps with the AT are a very real possible problem. Your goal is to choose a gear that lets you run in an RPM range where you getting into the upper torque band of the power yet you want to keep to the lower end of those RPM's to keep heat generation on the exhaust and engine side of the program under control. RPM's are your friend till your generating far more heat and friction than whats needed to get the job done. The Flat 4 in the subaru is pretty cool regarding its flat torque curve. When grinding over a long climb running the car at 3200rpms is more or less giving you nearly as much pulling grunt as you get at 4000 yes you might be going a little faster but 4000rpm is generating way more exhaust heat and friction with the engine than 3200 is and your speed pending your climb and load maybe only 10mph faster if that.

Thats where you lock into a gear pick an RPM that lets you cruise along in the slow lane doing what 50-45mph if your trailer load and climb is really that steep and you just let the car do its thing. No temp issues and your car survives the trip. Even my 4.7L V8 has made some trips where a 1800lb trailer 110 degree heat had us doing 45mph up a 19 mile climb to 8000ft starting at just 850ft. We wanted AC on to stay comfy and doing 45-50mph up the climb was no big deal. I could have done 70mph but for sure the AC would have been off and we would have been cooking some expensive parts.

The Subaru CVT works great in AT mode but on those long hot climbs pick a gear 3rd - find the 3200rpm mark and plug along if you can carry 4th at 3200 then the speed bonus is great. Jump it to 3500-4000 for a speed boost to get around slow traffic if needed etc. But I found our CVT and 2.5 will grind along all day long at 3200rpm without heating things up on the really tough climbs. I've been down to 2nd at 3200rpm a few times it gets slow but hey if you wanted a fast tow you would have bought a F350 Diesel which would have towed that trailer at 90mph with the AC blasting with no indication of anything getting hot.
Gee thanks Professor! If you had taken the time to read my previous (1st) post you could've saved much of the lesson. BTW: I don't tow with my OB, I have a F350 dually with a turbo diesel for that. ha ha:rolleyes::rolleyes: I was correcting my thought about the cvt being cooled with a oil/trans fluid heat exchanger which is common to most "regular" automatic transmissions. Other than that just passing on the Subie tech. comments. Your info about the rpm band is well taken.
 

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Gee thanks Professor! If you had taken the time to read my previous (1st) post you could've saved much of the lesson. BTW: I don't tow with my OB, I have a F350 dually with a turbo diesel for that. ha ha:rolleyes::rolleyes: I was correcting my thought about the cvt being cooled with a oil/trans fluid heat exchanger which is common to most "regular" automatic transmissions. Other than that just passing on the Subie tech. comments. Your info about the rpm band is well taken.
Freaking love the F350 sadly I have no sensible need for one. LOL I do get to mess with a family members once in a while though. But his is set up as a welding rig which is nearly max legal weight all the time.
 

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+1 I haven't towed that much weight yet, but have noticed that on an upgrade with speed control engaged that the tach is fluctuating up and down a bit. This is the computer adjusting the CVT ratio up and down trying to maintain the best economy possible but also adjusting for the increased load. I have to believe this minor "hunting" or shifting the CVT ratio generates some heat in the transmission. When I'm towing my boat (1200#) on the freeway this summer I plan to go to manual mode 5th on the CVT to let the engine rev a little higher, stop the ratio fluctuations on the CVT, and hopefully keep both the engine and transmission a little cooler. Even on my V8 pick-up I lock out the overdrive whenever I'm towing more than 1000 lbs, and my Subie is just a 4 banger, so it just seems to make sense.
Good explanation for my previous post of why you should not use cruise when going uphill.
 

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Discussion Starter #19
I have actually done a number trips with this trailer before. Prior to this happening I pulled the trailer over the Tehachapi mountains at equal temperature and steeper hills when going from West to East.

In relation to not using cruise control: it actually should make no difference as the lineartronic transmission is basically choosing the rpm on the basis of the speed you ask it to go. In order to maintain 60 mph cruise will adjust the rpms, increasing them as needed to maintain that speed. It actually does not hunt but acts as if you were pressing the accelerator to maintain a constant speed. It appears to be a direct mathematical relationship. Higher rpms as hill steepens to maintain same speed.

Therefore if you slow down on a steep long hill that should actually reduce how hard the transmission works, whereas keeping it in a lower gear will necessitate it spinning higher rpms which unless there is a special cooling fan built in which comes on when excess heat builds up, the laws of physics require the transmission to produce more heat at higher rpms.

In actual practice I watch the cvt gradually downshift which produces higher rpms to match the steepness of the hill and this is done linearly so that it is already doing what some suggest but faster and more efficiently than I could.

I am interested in whether it is possible to install a tranny cooler. Does anyone really have an idea if this is possible? Would you not need an opening into the transmission for hot fluid to cone out, go through a heat exchanger to dissipate the heat and then flow back into the transmission? From previous readings I thought this was not possible with the Subaru had set up the the cvt.

Thanks everyone for the input. Again my 2006 MT Outback never had a problem pulling this exact same trailer in higher temps with two kayaks added at tomes, and let us not forget 1400 lbs. Is less only about 50% of what 2013 OB is rated to pull.
 
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