Opinions Wanted: Bypass OEM Transmission Cooler?

[Blckshdw]

As I wait on a new radiator to arrive, the thought of bypassing the OEM tranny cooler, and running the aux cooler with built in thermal bypass by itself, crossed my mind. Since I'm in FL, we rarely see super cold temps. The few times we get near the freezing mark, is overnight during our short 'winters', and the truck is garage parked. So I don't think I'm gonna see the scenarios where the tranny fluid needs to get warmed up by the engine coolant.

For the most part, my drives aren't very long (distance, or time wise) usually under an hour. The transmission temp tends to read 20-30 degrees below the coolant temp. On the rare occasions I do longer trips out of town, I'll see the tranny temp climb after being on the highway for a couple of hours, then hit heavy traffic with a lot of idling, so not much air flow. One time I remember it getting up past 210, which I'm sure is still acceptable, but it's considerably higher than what I'm used to seeing, so that made me nervous.

Anyone know of any cons to this idea, that I'm missing? The return line is already connected to the aux cooler, so moving the other hose to the feed line wouldn't be too hard. Can't remember from when I did the filter and fluid change, how much dripped out when the lines were disconnected, so I'll have to make sure I have some extra fluid on hand just in case.

 

[littleblazer]

TC does lock up, tapped the brakes while doing 50, and saw the RPM needle do a quick hop. Got home and got under it, the trans pan was leaking from the drain plug. Tightened that down, and wiped it off. Not sure the seal is good enough, is it OK to use teflon tape on the threads?

Also found out the new radiator leaks. From the filler neck, just under the overflow tube, and both transmission cooler ports are wet underneath. Considered putting some teflon tape on the port threads too, until I saw the filler neck leak. So much for cutting a cost corner on that fix. Gonna try and get a refund, and order an OEM one later in the week.

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After that, figured I'd skip testing the cooler outflow. When I have to put in the new radiator, all that will get disconnected, so I can do it then. Tried testing the fan clutch. Turned on the AC, and hit the side of it with a rag. There was some initial resistance, but it stopped pretty quickly. Let it go a few times, and was able to stop it again with ease. No tugging at all. Safe to assume that's dead then?

I think so... I wish you were closer, my rad is just chilling in a box in the garage. I'd basically give it away to a friend but the shipping would probably hurt lol.

 

[Blckshdw]

I appreciate it man. It's sarcastically funny, I JUST got all my debts paid off from the spring, and was hoping the fall months would recoup the cash I dropped on that transmission. But here we go... I am thankful though, would be a major disaster if Dorian actually did cross through here like they initially forecast.

 

[Reprise]

That thread says lockup is being prevented cuz the engine is too hot. So if I'm not locking up, that's not gonna be the cause. I'll usually sit right at 195, sometimes dip below that depending on stops and starts.

Just to clarify (and I should have, earlier)... I thought the 'good' part of that thread started about 4 posts from the bottom of the page, where they start talking about the trans fluid temp sensor / resistance values, and how to test / isolate. The 'engine too hot' part, I actually discounted, myself.

 

[Blckshdw]

Just to clarify (and I should have, earlier)... I thought the 'good' part of that thread started about 4 posts from the bottom of the page, where they start talking about the trans fluid temp sensor / resistance values, and how to test / isolate. The 'engine too hot' part, I actually discounted, myself.

All good, I picked up a laser IR thermometer last night, and gave it some tests around the house. Always wanted one, shoulda gotten it sooner. When I get home from work, I'll test it out on the pan, see if it matches what's being reported. At this point, I was just happy the garage floor didn't have any new drips when I left for work this morning, and tranny fluid fumes didn't smack me in the face when I entered.

 

[Mooseman]

Pretty much. You can also confirm by jumping the relayémodule to apply full 12v+ to the fan. If it doesn't start roaring, it's toast. If you have a tuned PCM, you can go to a thermal.

 

[Blckshdw]

Pretty much. You can also confirm by jumping the relay module to apply full 12v+ to the fan. If it doesn't start roaring, it's toast. If you have a tuned PCM, you can go to a thermal.

Had a tune, stealership flashed it back to stock. I don't think I had the fan code turned off though anyway. Might be able to get the tune put back on (eventually) since it was an emailed file. You got a P/N handy for the thermal clutch, just in case?

 

[Mooseman]

Not off hand. Just lookup for 2009 TB fan clutch. You could still do it, you'll just get a code until tuned out. It'll probably outlive the truck (I kept mine from the 02).

 

[Blckshdw]

Fan clutch is definitely toast. Jumped the relay sockets, and nothing.

Took a closer look at the filler neck leak, turns out the reservoir hose is snug on the nipple, but not tight. Slipped on one of those hose clamps. Maybe this weekend I'll pull those cooler ports out, and give them a couple wraps of tape. Would be nice to not have to dismantle all of that stuff again for another swap.

 

[Mooseman]

The failed fan clutch would certainly explain higher tranny temps with less air flow through the eux cooler in traffic. Sucks that you lost your tune. Who did it originally? Maybe they can reflash it at minimal cost.

 

[Blckshdw]

Yeah that makes sense in traffic, but I'd think once you got to a cruising speed on open roads, that much air flow would be enough to bring it back down too (like the engine temps do). That's what caught my attention. But that trip to the beach, when I ran my AC on both legs (expecting the fan to be on), the engine was running around 206 most of the way. Didn't think having a hot condenser would make it run that much hotter than normal, but yeah if the fan was just freewheeling...

I got my tune flashed by a former member here, who's had a lot of life's responsibilities to deal with, so we haven't hung out like we used to. We were going to reflash my tune back in May, but couldn't get the timing right between our schedules. It'll get done eventually, just not able to pin down a time when. I was poking through HP Tuners last night, and I found the chart about the ECT and/or AC pressure vs desired fan speed. Since the thermal clutch doesn't get any of that data, is there any documentation on when it's supposed to activate, and by how much depending on temperature? Preliminary searches have been inconclusive. I might order it tonight, along with some other goodies, wouldn't get here until Monday though.

Edit: GMSI seems to indicate the clutch should engage anywhere between 185 to 205, but doesn't say how much.

 

[Mooseman]

It's variable. As the air it's pulling gets hotter, it moves more silicone into the clutch to engage it more. Except at startup for a minute or so, I don't hear it go hard but does pull more as it gets hotter. It's all by temperature, which makes enough sense that if the coolant in the radiator is hotter, the air will be hotter and will engage the fan more. This video explains it pretty good:

This design has worked forever but they tried to get fancy with an EV clutch, which was a failed experiment since they went back to thermal in 08.

Also, if the A/C pressure is higher, it will also be throwing more heat into the air stream to engage the fan more. Compared to the EV, it does pull a bit more all the time and doesn't take into account the speed you are moving. Might be a good thing for towing but may affect MPG a bit. The EV in my 07 is still working. I might just throw in the thermal just to see if my MPG takes a hit.

 

[Blckshdw]

lol my MPGs already suck, I don't bother looking at the gas prices when I pull into a station. Just fill up and go.

Thermal clutch has been ordered, should be here Monday or Tuesday, depending on storm related delays. Should get a good test on Wednesday, as I'm meeting up with an old friend after work, on the other side of the county for dinner. Evening rush hour traffic should leave things pretty toasty, and definitely not fully cooled down by the time I'll be coming back home. Would be great if a dead clutch is all my problem turned out to be.

 

[littleblazer]

It's funny, ford uses an EV fan clutch on the power stroke... and has the exact same problems with it. It's as reliable as the updated version was which wasn't horrible.

 

[Mooseman]

We should have had efans like the full size but they cheaped out on the rad so they had to overcompensate for it.

 

[littleblazer]

Yea but the full size didn't get efans until 07. Way into the life cycle of that platform. You can't really do efans on a gmt 800 either. Again the rad is mediocre.