Optimal Fluid Temperature + DIY Flush

[utc_pyro]

First question: What is the optimal opperation temperature range for the 5EAT's fluid?

 

I'm going stage 2 with my wagon, and installign a tramsmission fluid cooler to help with the added stress. I've found threads from people saying one can have too much transmission cooler. Also on threads talking about ones car warming up in cold weather, there was concerns about the transmission fluid being "up to working temperature" before going WOT.

 

To remedy this, some of the transmission cooler have bypass passages that apparently flow more through "bypass" passages when cold. I've also seen people have external bypass thermostats, but most of these are re-purposed oil cooler had have 180f+ set points. I'm not really sure if ether is optimal, thus why the operating temperature is needed.

 

Second question: Has any one "flushed" an 5EAT them selves before? Not just drain the pan and refill a few times, but attempt to

 

I found several guides for doing this on other cars (including my other car), but no sign that any one has done this them selves on a 5EAT. The fluid in mine doesn't smell burnt yet, but it's looking a little dark. I'm wanting to do this at the same time as the transcooler install.

 

Basic procedure I was planning:

1) Warm up car/transmission, then let the exhaust cool so I don't hurt my self.

2) Drain the pan.

3) Refill partially with new fluid

4) Change transmission filter (I know it's not need, but paranoid)

5) Install transmission cooler, but do not connect the return line yet.

6) Connect extra clear hose to cooler outlet line, run to large container with graduation markings on it.

7) Having the GF (or Roomate) help, start car and watch the fluid going into the container. Each time the fluid hits a new mark, add that amount to the dip-stick tube.

8) Once the outlet fluid is the same color as what I'm putting in, turn off car and reconnect return line.

9) Run car for a minute to get all air bubbles out, then top off.

 

Is this reasonable to do, or am I going to just cause a very expensive mess for my self?

[ebondragon87]

For your first question, don't know what temp range would be best but a trans cooler is a very good idea, I did one on my 02 Cummins (paranoid because they have horrid auto trans) and Supra when I swapped in a 1JZ.

 

For your second question, save yourself the trouble and huge mess and just have a shop you trust flush it. The average trans flush machine runs 12qts of new fluid through your transmission and it does it in about 15min, the way you described would take an afternoon

[ClimberDHexMods]

Do you have a temp gauge? If not, then it doesn't matter anyways.

[utc_pyro]

For your second question, save yourself the trouble and huge mess and just have a shop you trust flush it. The average trans flush machine runs 12qts of new fluid through your transmission and it does it in about 15min, the way you described would take an afternoon

 

$90 saved for an afternoon's work is still pretty good compared to my current pay rate. Also in this I'd get to learn something about my car.

 

Do you have a temp gauge? If not, then it doesn't matter anyways.

 

I'm going to be adding one (in a way) with the trans cooler, and need the information before hand to select the appropriate parts. I'm going to put a temperature sensor before the rad cooler, hooked up to PSoC running on an I2C bus with a few other sensors. I'm going to put a light in the gauge cluster similar to to the blue "cold" LED of the 2007+ cars that tells me when I can start pushing it.

[fishbone]

The best and quickest way to warm up ATF is to drive the car, not just let it idle, since in that situation the tranny isn't doing a whole lot and the ATF won't warm up, or at least not as quick.

158-176*F is quoted as being the temp you want the ATF to be at when you want to service the car. However it's perfectly fine draining the ATF when cold. It will just drain faster when hot I guess, just like engine oil. Bringing it up to temp is necessary only if you are going to run tests on it, such as shifting, etc.

 

According to the repair manual, the AT Oil warning light will come on when ATF temperature exceeds 302*F. As far as I can tell that's not much of a warning, more like an indication you just broke shit. Normal operating temps are 180*F or above, ideally not more than 230*F or so as far as I can remember.

Ideal place to install the temp sensor is in the pan, but good luck with finding the right drain plug that accomodates a sensor ...

[utc_pyro]

The best and quickest way to warm up ATF is to drive the car, not just let it idle, since in that situation the tranny isn't doing a whole lot and the ATF won't warm up, or at least not as quick.

158-176*F is quoted as being the temp you want the ATF to be at when you want to service the car. However it's perfectly fine draining the ATF when cold. It will just drain faster when hot I guess, just like engine oil. Bringing it up to temp is necessary only if you are going to run tests on it, such as shifting, etc.

 

According to the repair manual, the AT Oil warning light will come on when ATF temperature exceeds 302*F. As far as I can tell that's not much of a warning, more like an indication you just broke shit. Normal operating temps are 180*F or above, ideally not more than 230*F or so as far as I can remember.

Ideal place to install the temp sensor is in the pan, but good luck with finding the right drain plug that accomodates a sensor ...

 

Thanks, that was pretty much what I was looking for. I can select my parts with that info.

 

Any idea why the standard operating temperature for our cars is higher then many trucks? They quote just over 100F most of the time up to 150F in stop-and-go traffic, and that's towing crap.

[fishbone]

Who knows ... I guess that would be an answer for the techs that built it

To be exact, the repair manual says that you should wait until the ATF gets between 150-176*F before you mess with it. It was just my assumption that those temps are not the operating temps, rather a "good enough" spot to do whatever you need to do. So I may very well be off when I said 180. If it gets to 176 just idling, I don't see how it won't be at least 180 in traffic.

[ClimberDHexMods]

Ideal place to install the temp sensor is in the pan, but good luck with finding the right drain plug that accomodates a sensor ...

 

Have some faith

http://www.legacygt.com/forums/showthread.php?t=131811&highlight=M18x1.5

[fishbone]

Wow, THANKS for that

I have prosport gauges. Man ... the plug AND the adapter would make some serious sticking out I'll inspect the angle again and decide.

[KyLegacy 2.5GT]

I contemplated using the adapter in the pan as well until I looked at the angle it would be positioned at. If you put the adapter and sensor in place of the drain plug it is going to stick right out in the open. If any rocks or debris under the car hits it then say goodbye to your transmission fluid. If you can make some sort of shield to cover it than you would be ok.... but it would still be one of the lowest points on the car (a good pile of snow would rip it off). I took a brass t-fitting and installed that and the sensor in-line with the transmission cooler. If you follow the cooler install tread, you'll see a section for where you have to uses a double sided barb to tie the cooler hose into the flexible transmission hose, that's where I installed the t-fitting. This is the return line from the cooler to the tranny, not 100% true transmission temps but pretty close. I can take some pictures of the install if you want.

[utc_pyro]

I contemplated using the adapter in the pan as well until I looked at the angle it would be positioned at. If you put the adapter and sensor in place of the drain plug it is going to stick right out in the open. If any rocks or debris under the car hits it then say goodbye to your transmission fluid. If you can make some sort of shield to cover it than you would be ok.... but it would still be one of the lowest points on the car (a good pile of snow would rip it off). I took a brass t-fitting and installed that and the sensor in-line with the transmission cooler. If you follow the cooler install tread, you'll see a section for where you have to uses a double sided barb to tie the cooler hose into the flexible transmission hose, that's where I installed the t-fitting. This is the return line from the cooler to the tranny, not 100% true transmission temps but pretty close. I can take some pictures of the install if you want.

 

That's actually what I'm going to do. It seems simplest in the long run as it wont get in the way of 30k drain and fills.

[utc_pyro]

I found an interesting post over on the subaruoutback.org forums. They have the same cars as us, just with a lift kit? Why not go pocking around there:

 

changing Automatic transmission fluid (is easy)

 

It looks like some one use the method I ask about in the first post to flush a 4eat. That good enough for me to at least try it on my 5EAT. If something goes wrong, I'll have it tow to the dealer and drive my sludge-bucket for a few days. I'll take pictures ether way it goes .

[ClimberDHexMods]

^^^ I've told people this option many times on this forum, only to see the same people go and get a flush because their trusted mechanic (who makes WAY more on the flush he is also not liable for) says it's great. So now take that level of forum member, subtract people and make it worse...

 

While we're on the fluid temp thread, there's a great 3/8" brass coupler with 1/8 npt sensor port, sold by Jegs. I like this the best because it's one piece and cheap. This is after I mocked up a heavy McMaster pipe deal with 4 pieces to do the same thing . Fishbone tells me this placement isn't representative, but that debate is also sitting happy in some old thread. Fact is, I'm doing all placements to get data, and then removing the sketchy pan one. If you don't run over things, you won't hit the sensor. But that's all up to the driver.

[fishbone]

I think both the oil pan and the outgoing line are good places to tap into but will give you different readings. It depends on what you want, the line going to the tranny cooler will fluctuate more. I think I will go that route myself because I don't want anything sticking out from the bottom, nor do I want to drill a new hole into the pan, which would involve dropping it. Bleh.

[utc_pyro]

ClimberD, have you done this your self? I'm currious about how much fluid the 5EATneeds with this method. Also thanks for the tip on the sensor, I may do just that if I don't go with a thermostat with sensor ports.

 

Speaking of the thermostat, I'm going to use one. No one seems to make one that's adjustable, but I'm strongly considering the Earl 501ERL on my trans-cooler install. It starts opening at 160f and is wide open by 180f, so it looks well suited to the 5eat's range. It also has a few ports for sensors.

[fishbone]

No need for a thermostat if you are using a drop-pressure-type bypass cooler, such as the Hayden or TruCool line of coolers. KISS, aka keep it simple, stupid. Also, how do you envision the thermostat working since the ATF needs to always route through the lines since it is being pumped? Bypass? Again, KISS

[ClimberDHexMods]

No need for a thermostat if you are using a drop-pressure-type bypass cooler, such as the Hayden or TruCool line of coolers. KISS, aka keep it simple, stupid. Also, how do you envision the thermostat working since the ATF needs to always route through the lines since it is being pumped? Bypass? Again, KISS

 

I was looking at a bypass type thermostat by B&M, but I don't think it had sensor ports though those are easy to add anyways. It's like any thermostat, fluid goes one of two ways. So you would be adding 2 Ts into the loop. It is the best way to do it if you have the money, but there is no data to conclude that the second best way is or is not any worse. Though I'm not entirely sure our 5eat doesn't self-regulate to some level already. Frankly I have no idea what it does on it's own with regards to regulating temp, but it does have two temp sensors inside and a nice valve in it for the cooling lines. Not sure how it all works on its own.

[utc_pyro]

Yeah, but simple isnt as fun

 

I looked through the vacation pics, and there does appear to be a "cooler bypass valve" in the transmission, but it's not documented as to were it is or how it operates. I DO know that it changes the flow to the ATF cooler based on the lockup status. I THINK it blocks or restrics flow to the cooler when lockup is enabled. It appears that the return from the torque converter runs through the valve body, so this "cooler bypass valve" should be in there.

 

Search for "1. Lockup Disengage State".

 

What this tells us the transmission self regulates indirectly via lockup, but it does not do so based on temperature. I could be wrong, but I'd need more info to know for sure. If what I interpret the "vacation pics" to say is correct, then one may still need a thermostat for start up and cooler days, as the transmission will be sending all it's torque converter output oil to the cooler.

 

At the same time, it does show that it's not THAT BAD to not have one, as the cooler running highway miles will not be overcooled.

[ClimberDHexMods]

Yeah, but simple isnt as fun

 

I looked through the vacation pics, and there does appear to be a "cooler bypass valve" in the transmission, but it's not documented as to were it is or how it operates. I DO know that it changes the flow to the ATF cooler based on the lockup status. I THINK it blocks or restrics flow to the cooler when lockup is enabled. It appears that the return from the torque converter runs through the valve body, so this "cooler bypass valve" should be in there.

 

Search for "1. Lockup Disengage State".

 

What this tells us the transmission self regulates indirectly via lockup, but it does not do so based on temperature. I could be wrong, but I'd need more info to know for sure. If what I interpret the "vacation pics" to say is correct, then one may still need a thermostat for start up and cooler days, as the transmission will be sending all it's torque converter output oil to the cooler.

 

At the same time, it does show that it's not THAT BAD to not have one, as the cooler running highway miles will not be overcooled.

 

Good post. I do admittedly need to read through the AT section more. Gets pushed back by more urgent things unfortunately.

[subaru_user]

I wanted to post some transmission temperature logs that I took with RomRaider, and this thread looks like the best place to leave them.

 

The car is a 2008 Legacy Outback Wagon with 3.0R H6 and 5EAT transmission. Totally stock, no transmission cooler.

 

There were about 700 - 800 lbs of passengers & gear in the car, and it was also pulling a light boat trailer, maybe 800 lbs. It also had a bike on the roof rack for a little more wind resistance.

 

So, a reasonably heavy load for the car.

 

Ambient air temperature that day was about 22* C.

 

The X axis of the graph is in minutes, and Y axis is described in the legend by color (ie. road speed in KM/H, gear selection x 10 to make it easier to see, and ATF temp in *F).

 

In the first graph, the car was fully warmed up, and moved out onto an expressway. Just after 50 minutes into the logging, we hit a border lineup, and crawled along at idle speed for about 25 minutes. Then we jumped back up to highway speeds (80 - 90 km/h) after passing through. You can see the interesting effect that had on ATF temps.

 

The second graph was logged after the car had been parked for an hour, after the 1st graph log ended. About 45 minutes into that trip, we stopped for gas, shutting the car off but leaving the logger running. That explains the straight graph lines at that point.

 

Apparently there are 2 transmission temperature sensors in the 5EAT, both on the control valve body. One detects the oil pan ATF temperature, and one detects the ATF temperature at the torque converter outlet. RomRaider only allowed logging of one ATF temp sensor for me, and I have to assume from looking at these graphs that that was the one at the torque converter outlet, since even at idle speeds the temps are pretty high.

 

I want to do the same route with no trailer, and unladen, to get a real comparative benchmark, but this is a good start to posting objective data.

 

Enjoy, and post your own RomRaider ATF temp logs, too, if you have them.

[subaru_user]

Here is a log taken during a trip over much the same route.

 

But this time, the car was not towing the trailer.

 

The graph's X axis is minutes, and Y axis is as per the legend.

 

The outside air temperature was about the same as in the previous two logs (22* - 23* C), but the vehicle carried about 225 lbs less weight of cargo & passengers.

 

The highest observed ATF temperature over the route was 203* F this time, compared with 220* F when towing the trailer.

 

It looks like the transmission temperature generally averages about 15* - 20* F higher when towing the trailer.

 

Fishbone mentioned a normal operating range of from 180* F to 230* F. So when I'm towing that 800 lb boat trailer, the ATF is still in spec, although at the hot end of it (at 220* F).

 

So I'm not too excited to mount an aftermarket transmission cooler yet, if the trailer only costs me an extra 20* F.

 

It would be interesting to see someone who has an aftermarket transmission cooler, post their graphs.

[fishbone]

That temp range looks good but your ATF won't last, so be sure to shorten your drain and fill intervals.

[subaru_user]

I am bumping this thread, because I still have the same car, with the same light boat trailer, and I just took a long trip on Interstate 5 with it, through Oregon and California.

 

This involved crossing the Siskiyou Summit, as well as the notorious Grapevine pass into L.A.

 

I ran Romraider logger for a couple of hours around those summits, and thought that data would be interesting to add to this thread.

 

This time the trailer was probably more like 600 lbs than 800 lbs, and there was only the driver, so there was no passenger weight. It's clear that the significant load generated by this trailer on the car is the wind drag at highway speeds, rather than the weight.

 

The graphs are set up as in the previous posts, with the X axis in minutes and the Y axis as per the legend. For clarity of reading the graph, the gear position is multiplied by 10, and the engine RPM divided by 10. I only logged road speed for the Grapevine, and that's shown in kilometers per hour, so that the lines are separated better.

 

I put each route's elevation profile from Google Earth under each graph, and tried to line up the X axes to match. The Siskiyou graphs match a little better, probably because I hit traffic coming into L.A. and so the time on the Grapevine graph doesn't perfectly match the miles of distance on the elevation profile. It's pretty close, though, and you can see where the peak transmission temperature is reached at about the 95 minute mark, or about 115 miles on the elevation profile.

 

Peak transmission temperature was 228* F for the Siskiyou summit (at about 88 minutes into the log), and 241* F for the Grapevine summit (at about 94 minutes into the log).

 

The Siskiyou summit ambient air temperature was about 45* F at the time, and the Grapevine ambient air temps started around 65* F at the bottom, dropping to about 55* F by the top.

 

You can see that I held 3rd gear climbing the Siskiyou summit, but only held 4th gear for the Grapevine. For whatever reason, the car seemed to need the torque of 3rd gear more for the Siskiyou climb, than for the Grapevine. I'm not sure what, if any, temperature difference it would have made if I had dropped to 3rd on the Grapevine.

[utc_pyro]

It looks like the stock system keeps the temperatures pretty stable. If you go dig up the temps people see in cars natorious for transmission failures, they temps are MUCH higher.

 

Even with a thermostat mine acts kind of odd at low temps. Might be a good idea to add the JDM coolant-atf warmer/cooler in line with the air-atf cooler.