Inline aux transmission cooler hookup for A4LD

[fritz84]

• Hi, I have searched the archives (for this forum and elsewhere) and have not been able to find an answer to my question. New to me 1994 Ranger with 2.3 and auto trans (which was recently rebuilt under previous ownership). While I don’t plan to do any towing with this vehicle I do want to take care of the transmission, and installing an inline aux cooler seems to be a recommended as part of that program.
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• So, I purchased a mid-sized Hayden plate and fin style cooler and mounted it up in front of the radiator, which has the integrated cooler on the passenger side with a vertical orientation. The radiator was replaced by previous owner and that re-install appears to have resulted in cutting the upper steel line coming into the integrated cooler and installing a coupling to accomplish the reconnect. No such treatment affected the lower line, and both appear to be in good condition (not rusty or outward signs of damage).
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• Cutting to the chase- I believe the lower line on the radiator/cooler is the return line to the transmission and therefore the one recommended for install of the inline aux cooler. A easy/lazy install for me would involve taking advantage of the existence of that coupling on the upper (assume input) line which would avoid the need to cut into the lower line, and given the mounting location for the aux cooler, makes the length of hose provided with the kit workable. This raises the obvious question of if it will do any harm installing inline on that line, or will it just potentially be less efficient in that position?
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• Lastly, I’m located in a moderate climate zone that rarely has freezing temps over extended periods, in case that figures into the calculations. If there are any other considerations involved that I’m not aware of I would appreciate haring about them- please advise.

 

[Grumpaw]

These are the two methods and proper routing for an aux. trans cooler.
Cold temps really don't matter as, except for very very cold temps, the cooler the fluid the better.
I'm in Va, and run coolers on all the vehicles I own, including up coming on my Ranger. Going to run a 60 plate stacked cooler on mine, about the biggest you can get.
Grumpaw

 

[Dirtman]

I installed mine on the upper line and it still greatly reduced temps (consistently 175). I actually think the upper line IS the return line... dunno, but like you, the upper line was just waaaaay easier to use than the lower.

Either way I dont think it will matter. The radiator temp runs constant and is right where the trans fluid temp should be so cooling it down before or after going through the radiator is equally effective In my opinion. I also think it's best to keep it running through the radiator because as previously stated, the fluid should be warm and the radiator provides the constant proper temp. The aux cooler just spills off additional unwanted heat.

 

[Grumpaw]

I didn't mean to imply that trans fluid should be "cold". It needs to warm to a good operating temp to be effective, ideally between 175 and 195.
With any aux cooler, your 2.3/auto combination shouldn't ever get "hot" unless your towing or hauling a real heavy load.
Been towing campers, running motor homes, owned high preform. cars, each equipped with coolers, and never ever worried about temps, and never lost a trans.
With our small engine/trans combo's and light loads, as Dirtman posted, bottom line is that it will work any way you hook it up.
Grumpaw

 

[Dirtman]

Before I installed my aux cooler I managed to overheat the trans hauling concrete through PA hill country. Did they same thing after installing the aux cooler and she never went over 185.

Big believer in adding lubeguard red to the fluid too. It's the only additive that doesn't seem to be snake oil and is actually recommended by manufacturers.

 

[fritz84]

Very much appreciate your feedback on this! I'm inclined to go ahead with the easy hookup on the inline aux cooler using the upper line (regardless of whether it is the return or input from the transmission).

I have seen variations of that diagram in different places, and got one with the kit I bought. It seems the recommendation of installing the inline aux cooler is consistently on the return line to the trans, for whatever reason. If there are any engineers versed in fluid dynamics out there looking in that could offer additional insight on why that is the convention I would be interested to know, at least in layman's terms.

Approaching it as a thought experiment the only rationale I can come up with is that pre-cooling might might be less efficient if the factory cooler in the radiator subsequently brings the fluid temp up. However, based on the information you all have just provided, that temperature is calibrated for the system and so should be ideal, as long as the system is able to keep up under loads.