Aux Transmission Cooler

[sennister]

I have a 2011 Denali and it has the KNP (Cooling, auxiliary external transmission oil cooler). I think it might be standard on Denali trim level trucks. Anyhow we bought a new camper this spring and went out on our first trip this past weekend. I normally keep an eye on transmission temps while traveling with it. The trip was pretty short but the area we went was pretty hilly. Air temps were in the low to mid 70s and I was hitting 210F on the transmission. With our old camper we would rarely get that hot unless it was well into the 90s but this new camper is quite a bit bigger and heavier. In fact if we went any bigger we would have traded in the Denali and gone with a 3/4 ton truck. It is well within the towing rating and we are not exceeding axle limits or hitch limits which is really the limit not the 8100lbs that they claim in the brochures. I haven't gotten it to the CAT Scales yet but I would estimate that we are at about 6000-6250lbs.

Anyhow while I know 210 isn't really hitting a limit where I should pull over, it has be wondering about what it will be at when it is in the 90s? I was thinking about adding an aux transmission cooler but it already has one. Anyone else out there run into this? Should I pull the aux cooler and put a bigger one in or add a third cooler? Right now it first goes to the combination transmission/oil, then it goes to the Aux cooler and back to the transmission. I could probably fit in a second aux cooler somewhere.

Because of the towing I do the severe service interval and it gets new fluid every 50K. I also am running the synthetic fluid. Maybe it is nothing to worry about since these newer transmissions seem to run hotter than they did in the past and the synthetic won't break down as much at 220 compared to the older stuff.

 

[PG01]

With the synthetic and cooler i think you are fine with those temps and that load.... i was getting up to 190-195 (depending on speed and air temp) on my trip to fl last month with a tiny 5x8 ...... i think you doing pretty good again with that load and those temps...if you really want to get a bigger cooler like you said...it may help a few degrees... thats a big load ya know. my 13 hoe has the hvy duty (ha) tow pkg and the cooler is right in front of the rad behind grill easy enough to swap out.

 

[sennister]

Yeah that is the same aux cooler that I have on mine. I was just expecting temps a bit lower than 210 being air temps (low 70s) were not that hot out. I wouldn't think much of it if we were in July with air temps in the high 90s. I guess the good side is that with the OEM aux cooler the lines are already there so it would be really easy to just pull the OEM and slap a bigger one in its place.

 

[sumo]

210 is still ok. I hit 210 on a hot summer day and I don't have a cooler in mine. 250 is killer. Have you done a fluid and filter change yet?

 

[sennister]

210 is still ok. I hit 210 on a hot summer day and I don't have a cooler in mine. 250 is killer. Have you done a fluid and filter change yet?

Yeah, the point is that 210 on a hot summer day I am fine with as well. However I was seeing 210 at 73F or so means that when it is 90+ it probably won't be at 210 anymore.

Filter and fluid changed about 40K ago and getting ready to do it again. This is why I am considering addressing this now. As long as I am draining fluid and filter I might consider changing out the transmission cooler at the same time. It will get a little more of that old fluid out.

I was talking with some people in a camper forum and one person said that he added this to his 07 Suburban. One nice thing is because I have the Aux cooler the lines are there already. I unbolt the existing one and hook this one up. It also has a thermostat so it won't pass fluid through it until it hits 180F. Being we live in MN it is possible to have -20F days and having a big cooler like that on the transmission will mean it will never warm up to operating temps since we don't do much camping in the winter.

 

[navi]

Yeah, the point is that 210 on a hot summer day I am fine with as well. However I was seeing 210 at 73F or so means that when it is 90+ it probably won't be at 210 anymore.

Filter and fluid changed about 40K ago and getting ready to do it again. This is why I am considering addressing this now. As long as I am draining fluid and filter I might consider changing out the transmission cooler at the same time. It will get a little more of that old fluid out.

I was talking with some people in a camper forum and one person said that he added this to his 07 Suburban. One nice thing is because I have the Aux cooler the lines are there already. I unbolt the existing one and hook this one up. It also has a thermostat so it won't pass fluid through it until it hits 180F. Being we live in MN it is possible to have -20F days and having a big cooler like that on the transmission will mean it will never warm up to operating temps since we don't do much camping in the winter.

I added the trucool 40k to my Silverado 1500 4x4 due to seeing similar temps as what you've mentioned when towing my boat or other trailers. Since swapping the factory aux cooler for it ( rather simple install if you buy the right fittings it just plugs into your existing lines ) I haven't seen temps above 180 while towing and rarely break 150 on normal day to day driving in south Texas heat. Very impressed and will be adding one to my wife's 2017 Tahoe even though it will rarely see a trailer behind it.

 

[sennister]

I added the trucool 40k to my Silverado 1500 4x4 due to seeing similar temps as what you've mentioned when towing my boat or other trailers. Since swapping the factory aux cooler for it ( rather simple install if you buy the right fittings it just plugs into your existing lines ) I haven't seen temps above 180 while towing and rarely break 150 on normal day to day driving in south Texas heat. Very impressed and will be adding one to my wife's 2017 Tahoe even though it will rarely see a trailer behind it.

Are you concerned at all about hitting minimum transmission temps?

The person that sent me the link to the Trucool 40k is reporting the same that he doesn't see temps over 150. However he didn't think installing the bypass was worth it. His truck (07 Suburban) didn't have the OEM aux cooler so he had to plumb everything in. He is in Ohio I think so he gets a winter but not as cold as what we see. I could block it off partly in winter but I think the bypass is easier.

 

[navi]

Down here in Texas I'm not very concerned about it. In your neck of the woods I would buy the model that comes with the temp bypass. My understanding is they recommended the models with bypass for areas that frequently see freezing temps. We don't see that too much here or I would have to move further south

 

[sennister]

Down here in Texas I'm not very concerned about it. In your neck of the woods I would buy the model that comes with the temp bypass. My understanding is they recommended the models with bypass for areas that frequently see freezing temps. We don't see that too much here or I would have to move further south

Yeah this is kind of my thinking. The one I am looking at has it. I suspect this might be why the one that the OEM uses is not all that big.

 

[PG01]

Yeah this is kind of my thinking. The one I am looking at has it. I suspect this might be why the one that the OEM uses is not all that big.

Yeah, its cute, tiny little thing..... BIG BAD GM HEAVY DUTY TOWING PKG....with a wee little cooler.....lmao