Transmission cooler lines leaking

[earnies2]

I noticed my transmission lines are wet.. not leaking but they need to be replaced. I was thinking on adding a cooler like on Freightliners have on the frame behind the cab. So I would come out of the trany go to the cooler behind the cab then to the cooler in front of the radiator then back to the transmission is that a good idea and will it help to keep the transmission cooler? Is it worth it? I need to replace the lines and I think I have the cooler in the shop so the only expense would be the extra lines and fittings.

[Waterloo]

(06-16-2021 )earnies2 Wrote:  I noticed my transmission lines are wet.. not leaking but they need to be replaced. I was thinking on adding a cooler like on Freightliners have on the frame behind the cab. So I would come out of the trany go to the cooler behind the cab then to the cooler in front of the radiator then back to the transmission is that a good idea and will it help to keep the transmission cooler? Is it worth it? I need to replace the lines and I think I have the cooler in the shop so the only expense would be the extra lines and fittings.

Is this a ProStar, I forget what you have? Assuming this is air cooled too? If my assumptions are correct, I would simply replace the lines and call it a day.

[Chamberpains]

That's is a horrible idea to add another cooler and more lines that will potentially leak and take abuse. The KISS (keep it simple stupid) method works great. Most if us that dealt with trans coolant heat exchangers simply went to an air cooled cooler that hangs off the back of the trans or mounts somewhere up out of the way from road debris. My transmission gets to 180°f at its hottest. Most of the time it never moves the temp guage.

If your trans is running under 230-240°f then it's doing its job. If it's getting up to 250°+ then there is either a problem with the cooler or the trans or the pump in the trans. Fix it. I don't know of a hauling scenario that would require anything more then a well placed single cooler. If your just a standard freight hauler then the simpler the better will do just fine for all scenarios.

[Hamish]

My 2c on an old post: I removed the air tranny cooler on my 2007 9900i when the hose burst upon starting in cold weather. Why would I want my tranny to be that cold? Replaced with a coolant exchanger and my tranny oil is warm before I drive, better shifting, better fuel economy - hot tranny was and still isn’t a problem hauling 140000 even in 90 DegF.

[Chamberpains]

It's not that heat exchangers are bad at what they do. It's the awful fact that when they fail you get coolant in the transmission and gear lube in the coolant. Your heat exchanger becomes a fluid exchanger.

Most of us opted to take this possibility out of the equation. It happened on my T660 and it is an awful mess. Plus I had to lay in the mud and bypass and temporarily block off the trans from the coolant system till I got it home and was able to flush both the trans and the coolant system many times.

On top of that the Port of Baltimore was not to happy with the mess I made on the pier as it vomited sludge out the breather on the transmission before I caught it. Then I of course had to drain some out on site to not have the trans over full and blow out all the seals. I went through 4 full rolls of paper towels trying to catch enough sludge as to not just straight up make a hazmat spill on the pier. It wasn't pretty....

[Rawze]

Chamber is right. Those heat exchangers for trannies tend to rot out after 500+k miles (or 6+ years) and it ruins the tranny in a hurry when they do start seeping. I have seen this time and again. This is why a lot of people have switched over to using air-cooled heat exchangers instead.

It is far less of a hassle to deal with a leaking tranny line that is going to an air cooled heat exchanger as they age, than it is to find out the hard way one day that coolant has been seeping into your tranny and now the tranny needs a $4,000 rebuild.

ref: http://rawze.com/forums/showthread.php?t...3#pid28933

Some people may have a specific need to use a coolant-based heat exchanger on their tyranny .. but otherwise, I would say it is not really a good idea vs an air cooled one. Using a good quality brand of synthetic oil in the tranny otherwise is just fine for dealing with those winter months and cold applications for most people. My air cooled tranny lived a very long lifespan and I drive in the coldest of environments in winter months just like anyone else would that hauls freight across all of the 48-states.

Hear is a link to my own tranny tear-down after 1.4 million miles and it had not being touched internally. It is in a prostar and it has always been air-cooled : http://rawze.com/forums/showthread.php?t...6#pid52116

[Hamish]

I totally agree that an exchanger adds a risk. 500k miles on the cooler will be when the truck reaches 2,000,000 km, so I will make a note in my service checklists to be proactive and replace it at that point.

I do drain a little oil out of the tranny at each major service interval with the hope that I might notice any coolant leaking into the oil before it becomes big. I probably checked my tranny oil for coolant three times in the month after I installed that exchanger!

I'm OK with the added risk in my case because I turn the truck off to sleep, even outside in the winter down to - 20 DegC. That stiff oil in the tranny pump blew the air exchanger hose right off after starting the truck and I would have lost my tranny due to no oil in short time if I had not done a second loop on my pretrip and noticed the rapidly growing puddle. Love having a warm tranny a few minutes after starting the engine (Espar engine heater). The truck was starting to slip out of gear under heavy load when I first got it at 910,000 km with original tranny. Used to hold it in gear, just in case at times. Changed the oil, (synthetic of course) and figured I would have to have it rebuilt as soon as I had some down time. That truck/tranny is now at 1,313,000 km and no more tendency to jump out of gear at all, which really surprises me.