External Transmission Cooler 5HP19FL

All,

I've searched this site, and the interweb, but I've not found an answer.
Has anyone installed an external transmission cooler on a Passat tdi automatic trans (5HP19FL)? I've put an external cooler on every automatic transmission I've had, and they help immensely.

I'm wondering about fitment and size.

Thanks, Dave.

No, but you do know that it goes through the radiator correct?
The ideal place would be right side below the frame rail. Opposite side from the turbo intercooler.

Do you think a front mounted cooler would adversely affect the radiator? I've never seen a side mount transmission cooler other than ones with built in fans for remote mounting due to space constraints. Ive installed many aftermarket coolers or upgraded oem ones to double or triple the size, all mounting in front of the radiator. Ive also never searched for a side mount.

While i had my passat front bumper off i remember looking at my old oem 7.3 psd cooler on the ground (seemed a perfect size) and thinking why didn't vw add one of those, i probably wouldn't have so much 5 speed conversion how to info to read about.


I think there would be room enough up there for both a fmic and transmission cooler if one was inclined to install them.

Not much need for one, given that transmission's prolific use of lockup and the engine's V8 levels of torque that allow for it.

However, if you really wanted to install one, the Audi Allroad A6, with the biturbo 2.7L V6, has an extra one. It lives off on the driver's side, down low, and is plumbed into the regular cooler.

That car weighs more, and makes a lot more power... that is why it has one. That said, unless you actually see the ATF temps getting up to a level to be concerned with (which you won't, because the TCM monitors that, and adjusts its behavior accordingly, and if it STILL could not get the temp under control, it would flag a DTC for ATF over temp control range... which I have never seen).

Ooooh thanks for reminding me OH. I have one of those coolers left over from my AllRoad TDI conversion 2+ years ago. I will gladly sell it for a great price.

It’s always funny to me the inadequate cooling on most oem automatics especially the 01M with it’s sealed cooler system so the coolest it can possibly run is engine coolant temp which according to fluid manufacturers shortens fluid and trans lifespan then VW says 100k service interval which is twice as long as it should be if not 3x as long....

vwztips said:

Ooooh thanks for reminding me OH. I have one of those coolers left over from my AllRoad TDI conversion 2+ years ago. I will gladly sell it for a great price.

Click to expand...

How much you thinking of selling it for?

I do remember reading about oil coolers and for every 10 degrees lower you could get the fluid at normal running temp it would add X amount of miles to your transmission. I believe it was regarding a 700r4 or 4l60e or other domestic vehicle.

Would be interesting to install a transmission temp sensor in the pan to get a reading both before and after install on a hot day pushing her hard.

My 4r100 even has aftermarket extra deep pans available with cooling fins to pair with my extra large cooler. I don't tow often enough to justify the pan.

I make even garbage chrysler 42re transmissions last for ages by installing external coolers, and keeping them out of overdrive until at least 80kph (50mph). Hot trans fluid kills transmissions, as does hunting in-and-out of overdrive.

I also change fluid every 100K kms (60K miles). I knew a guy who guy who owned two transmission shops, and he said if people did that, 3/4 of trans shops would be out of business. There's nothing magical about a ZF, and "sealed for life" is a good way to destroy a transmission that could have lasted much longer.

I change the fluid in all my domestics every 30k miles and it’s dark usually and they all have over 200k. Wife’s Tahoe 4l60e has 230k miles and no issues.... keeping it cool but not cold is key!

Passat W8 also has an external cooler for the 5HP19 and could be direct fit if you obtained all of the lines.

City miles or highway miles must make a whole lot of difference in the life of the tranny. Much less shifting on highway.

To cool fluid isn't great either. I'm not sure your going to get much difference with your Passat. Like a few have said, that trans is used in heavier and applications with more power. Changing the fluid regularly will help out more than a cooler IMO

Too cool

Actually these transmissions tend to run too cool most of the time if ambient is under 10*C. Unless you live in a city with 1st-2nd gears drives, it takes forever to get the trans fluid temp up to 40*C and then it barely gets up to 65-70*C and that is with an external inline thermostat. When engine coolant is 80*C the trans is at less than 35*C so the radiator does not help with trans warm up. On the contrary it cools the fluid in stock configuration. I have an external spin-on filter and a 77*C rated thermostat installed to avoid the coolant radiator up to about 70*C yet I only gained about 5*C temp increase in warm up on the morning drive . The last 5 months of cold weather the temps stayed at less than 60*C most of the time except 2-3 instances of low speed traffic in the hills part of the city.
On the other hand if it's summer or the car is driven in traffic 1st-3rd gears fluid in the oil pan gets up to 100*C or more and at the outlet pipe to the cooler where the oil comes from the unlocked torque converter it is even higher. The factory heat exchanger in the coolant radiator is too small to cool the fluid in these circumstances.
That's why I plan to use the factory trans cooler for power steering as soon as I install the air/oil Setrab radiator. I will also install an Audi A6 water/oil heat exchanger on the warm-up path from the thermostat. It will be plumbed between the heater core and the engine. It will serve also as a backup cooler in case the thermostat brakes down.

First step cooling upgrade

This is what I have done for now.
http://pics.tdiclub.com/showphoto.php?photo=130309&title=trans-fluid-warmup-step-1&cat=500

I have a complete factory setup from a W8 passat if anyone is interested. That setup has a thermostat.

What temperatures were you seeing with that thermostat?Was the cooler is series with the cooler in the coolant radiator?
I bought one like yours but it seems too small so I plan to use it for Pwr Steering on my 1.9 AVF 4 Motion.

Trans warm-up and cooling

I made some sketches with the planned final setup. Pictures http://pics.tdiclub.com/showgallery.php?cat=7052

Since nobody has any questions or comments, here are my concerns.
In warm-up using the coolant/oil heater will I have difficulties warming up the passengers compartment? I do have a Webasto stationary/additional engine heater that I should install but I don't believe there is enough space for it after the heater install.
In temp control will the fluid temp in the oil pan fluctuate up and down instead of staying at a constant temperature regulated by the external thermostat? The engine coolant temps in my engine tends to stay at 92-94*C(198-201*F) normal operating. The external trans fluid thermostat is fully closed at about 82*C(180*F).

Transmission and converter flush

Replacing all the trans fluid on most cars is next to impossible because of the fluid in the torque converter. Some manufacturers, like Mercedes,installed a drain plug on the converter to solve that.
On the side of these 5HP-19 transmissions there is a 10x1 mm plug on an internal passage that communicate with the torque converter. It is basically the feed to the converter. I did not try yet but I believe that pushing clean fluid through that passage will eventually replace all the dirty fluid from the converter. And I believe the better part of the dirty fluid would exit through the cooling out line. Disconnecting the line between the trans and external filter can let us know to stop when the fluid coming out is clean.
Than we can replace the external filter and flush the coolers and even fill the rest of the transmission before it is started for final level adjustment.
These are the other benefits of the cooling modifications I am doing. Lines are -8AN and disconnecting and plugging lines to flush the trans and coolers is not that difficult.
Anybody tried this before?

Flushing the Torque Converter is possible using the WK AUF galley but there is too much fluid going to the oil pan which is a waste. I used this method on 2 6HP19 transmissions, a BMW and an Audi A6 that I own now.
I will do some more homework to see how can I restrict the flow back to the valve body and, if successful, that will be the best way to flush the Torque Converter only with the least amount of fluid used and minimal mixing of old and new fluid in the converter.