Add on Transmission Cooler, common mistake

[bbally]

Thought I would post this just in case someone is putting one of these things on to a vehicle.

I recently rebuilt an A4LD with the help of the fine content on this site. My first automatic rebuild. Pretty darn easy for those wondering whether to do it or not.

Anyway I am an engineer by training... I noticed the previous owner had a transmission shop install the aux trans cooler as suggested in many spots on the site when dealing with an A4LD in the 4X4 configuration.

The dope that put this thing on had it on wrong.... the oil was coming out of the transmission, through the aux cooler, then into the radiator trans cooler, then to the transmission.

Just from an engineering standpoint, they are taking good outside air and cooling that fluid down, then they were running it into the radiator to get heated back up prior to hitting the transmission.

Anyway as an engineer I am OCD to the max, I have been looking at lots of aux systems when I see them in the grill, about 30 percent are on the wrong way so as not to provide any additional benefit to the operating temp of the fluid, So take a look at the plumbing if you are putting one on or purchased a truck that already had one installed, some people don't put it on correctly.

 

[manaen]

Well the theory is, that it will not over cool the transmission. The problem is Ford transmissions (AFAIK) all have a cooler bypass system that will not let the transmission over cool itself. Anyway many manufacturers even recommend that their coolers be installed the way your cooler was just so they are covered in all applications.


But with our transmissions you really cannot over cool them, but you can over heat them!! so your assessment of the install is correct..

 

[ExploringNC]

I'm getting ready to install an aux. cooler on my '98 that should be pretty neet when I get done.

I plan on putting it inside the left fender. I will have a side vent sealed off with a nacaduct (the thing in the side window of a race car that allows air into car) on the back side of the vent. I will run a brake duct from the nacaduct with a brake blower to the cooler and have a switch to turn blower on or off.

I mainly wanted this setup for trail riding when you don't have much air flow threw radiator. I didn't like the idea of putting the cooler in front of the radiator as I felt it would restrict air flow and I wanted it somewhere safe from punctures. I have all the parts I need already and even an external tranny filter I just gotta find the time to start a new project.

 

[manaen]

Be sure to post pictures of your work, sounds like an interesting install that others (including myself) would like to see

 

[Maniak]

From what I remember about the inside of the a4ld, it does not have a thermal bypass.. meaning its always running fluid in the cooler... That means if you you ran it from trans to radiator to cooler you could "in theory" over cool the fluid..

In my area thats practically not possible.. I either run mine from the trans to the radiator into two coolers or I bypass the radiator in general.. In summer I run w/out the radiator.. In the winter I let it go into the radiator first.

~Mark

 

[manaen]

It would be interesting to know which Ford Transmissions have the bypass and which ones don't. Thanks for the info Mark, BTW do you have a valve system setup to switch setups or do you manually switch the lines?

I'm not too sure the bypass is a good thing, as I could see a situation where the bypass stops working and the tranny fries itself. That is one reason I put a PSI gauge on my external filter, so I can see when the tranny is pushing fluid through the cooling lines and when it is not. For the most part from what I can tell, even on cold days it will push at least 15 PSI while moving. When things get hotter it goes up to about 35-40 PSI max.

 

[Maniak]

Currently, I move the lines by hand, its a messy job, but someone has to do it .. I wanted to put valves on there but I want it to be a single valve. I looked at using two valves and I was afraid I could accidentially set the wrong and block the cooler fluid and fry the trans..

I bypass the radiator and use only the external coolers (two with a fan) becuase I can get 160-170F pan temps in summer heat when I'm going through the radiator.. If I pull it out of the radiator my trans temp stays 150F or so..

Keep in mind, I'm not running an a4ld anymore.. I'm now running a 700r4 with a 2800rpm stall so it gets hot quickly/easily..

As for which transmissions have the bypass, Glacier may be the one to answer that, I only remember flow all the time and have information from glaciers threads..

oh yea, I do have a pressure gauge on the transmission, but I'm reading line pressure, not pressure at the external filter (I have one too).

~Mark

 

[studd469]

What happens when you over cool your trans?

 

[Maniak]

When its too cool the fluid gets thicker and gives you higher pressures.. I don't know what "too cool" really is..

I put mine back through the radiator becuase we were getting 18F degree mornings and on my drive to work (almost all freeway) my temp never came up off the peg (I think 100F).. I can see my line pressures and I don't think mine ever got too bad but they definatly were higher..

For example.. my Normal operating temp line pressure at idle in gear is 80psi or so.

When cold (first thing in the morning) with same idle speed in gear I'm getting 100-120 psi (over 100psi)..

I don't know how bad it really is to have higher pressure OR if that is the only issue with over cooling a trans but its what I noticed.

 

[manaen]

well I believe is it a omnidirectional problem, in the worst of cases the fluid could be too viscous which could cause tearing of the film and result in metal to metal contact. The same thing could also happen in your engine on really cold days, that's why it is good to let your engine warm up a bit before driving. Also the increase in thickness could cause extreme pressures in the valve body which can kill your valve body in many ways. However, this would probably only occur in northern (colder) regions where temps are well below freezing for extended periods.

If you are worried about it, make a winter cover for your cooler, but watch your temps cause even in the winter the tranny will heat up when under load

 

[manaen]

Maniak you beat me to it