Tranny Cooler Line Routing?

[ExpoMike]

Does it matter which way the fluid flows through the tranny cooler?

My lines route better if I have the hot side going in the bottom of the cooler and cooled side coming out from the top. I am bypassing the stock in radiator "cooler" so that does not need to be taken into account.

Thanks!

 

[madizell]

If there is a difference, it would be so slight as to make no practical difference to you. Air flow is more important, IMHO.

 

[Scenic WonderRunner]

I have had this same question.

And I am considering adding an aux tranny cooler.

Can I re~ask the question.....for my Toyota?


Is it better to route the fluid lines so it flows through the stock radiator cooler first, before the aux cooler. Then on to the tranny After the Aux. Cooler.

OR..............

Is it better to route the lines to flow through the Aux. cooler first?......then through the stock radiator cooler and on to the tranny.


AND...............

Why can't you use both?



.

 

[ExpoMike]

Hi SWR, long time no see.

As for your question, IF you are keeping the stock, in radiator cooler in the system, then the typical method is tranny out>stock radiator cooler>aux. cooler>tranny in. The idea behind this is to warm the fluid up quickly in colder climates.

The drawback to this method in warm/hot climates is that the engine typically runs in the 190*-220* range which is typically inducing heat into the tranny which is a bad thing. Ideally if you can get the tranny to run in the 150* range, it will add a lot of life to the tranny, fluid and parts.

I am bypassing my stock radiator one and going with a large aftermarket unit. I have also installed a tranny temp bypass which routes the fluid back into the tranny below 150* and only to the cooler when higher then that. This allows it to warm up correctly in cold weather but does not add the heat from the engine into the tranny.

My .02 worth. I just wasn't sure if the flow through the cooler made a difference.

 

[goodtimes]

I was once told, by a design engineer for GM, that it is actually possible to over-cool the trans fluid. He recommended running it through the aftermarket cooler first, then the in-radiator (OEM) cooler.

As to which way to run it through the aftermarket cooler....doesn't generally matter, for the reasons others have cited.

 

[ntsqd]

I run them in at the bottom and out at the top when given the option. That makes them self-bleeding of any embolized air that might be in there. It also forces the trans to pump the fluid thru the cooler rather than allowing it to 'fall' thru the cooler. My thinking is that fluid dwell time in the cooler would be slightly longer this way so why not take the greatest advantage of it?

Over cooling is an issue in cold country, but not really in the South West. To me the most ideal for all climates is radiator cooler first, then aux cooler with the mentioned oil thermostat placed such that it by-passes the aux. cooler when cold. That way the aux cooler is only working when the trans really needs it.

 

[ExpoMike]

Thanks a bunch guys!!!! :exclaim:

I knew I could count on you all to have a good answer for this. Looks like I will route it the way that the lines work the best.

I did add the t-stat in line. It's made by Long of Canada who is an OEM supplier so I figured they knew what they were doing.

 

[madizell]

First, I don't have access to engineering specs, so can't answer with absolute confidence, so this is largely opinion mixed with theory, but as to whether to route to stock cooler first, then auxiliary cooler or vice versa, I believe it would depend on whether the stock cooler is co-located in the radiator. If so, "cooler" may be a misleading description of what the device is intended to do.

The question really is whether the transmission, normally, runs hotter than 200 degrees, and I believe that without a cooler of some sort, most automatic transmissions will run hotter than that. If so, running transmission fluid through the cooler located in the radiator will generally bring the temperature down to around 200 to 220 degrees. It is a "cooler" only to that extent. A transmission intended to operate at that temperature would not want a regular influx of cold fluids.

Stock cooler tanks co-located with the radiator are more a temperature stabilizer than a cooler, and to some extent they do warm fluid faster on cold mornings, which is a good thing. If the transmission is working normally and the fluid is not cooking off or burning, then the system is working normally and an extra cooler is not needed. If your transmission needs to run at a stable temperature in the low 200's, adding a cooler after the stock cooler would defeat the engineer's intentions.

But if the transmission is running a bit hot, and needs to stay in the low 200's, putting the extra cooler first might help bring the temperatures down quickly without taxing the radiator's power to cool the fluid down to normal operating temperatures. In other words, with a hot radiator the stock transmission cooler located in the radiator will have a high threshold and have difficulty dropping fluid temperatures to the intended level. Cooling efficiency decreases when the temperature of the fluid and the temperature of the "cooler" are close together. In this situation it would help to have an auxiliary cooler, but if you still want to regulate the fluid temperature, putting the auxiliary cooler after the stock one would leave you with cooled but unregulated fluids. You would never really know what temperature fluid you were returning to the transmission.

So, I would agree that it makes sense, if you must, to plumb the auxiliary cooler between transmission and radiator, and let the radiator regulate the temperature of the fluid being returned to the transmission, rather than the other way around. If, however, your stock cooler is a stand alone passive cooler, adding an auxiliary cooler only increases cooling capacity, and whether one comes before the other would be moot.