Done towing. Disconnect trans cooler?

[HawkeyeScott]

2008 Chevy Suburban 1500, 4L60E. Installed a Tru Cool LPD transmission cooler in 2017 after buying an RV. Worked great.

We’ve now sold the RV, which means my original need for the cooler is gone. Temps rarely sniff GM’s stated operating range (around 190 I believe), even in summer. 165 is about it.

Should I disconnect the cooler or leave it in place?

Put another way, am I risking any issue by running ATF that is consistently below GM’s desired operating temp?

At what point would any moisture burn off? Fluid looks great on the dipstick and the truck, knock on wood, shifts fine at any temp.

Top of mind this weekend as I prepare for the usual 15k pan drain/refill…

 

[ctechbob]

I'd think @clinebarger could comment a little more authoritatively than I, but I was under the impression that 4L60E's couldn't run cool enough (within reason). I'd leave it.

 

[Oil Changer]

Leave it. Heat is never a good thing for transmissions.

 

[eljefino]

Had an 08 Silverado 4.8/4L60E with electric fan. Only time the transmission exceeded 150-160 was when the radiator itself was "sweltering" in traffic on a hot day.

IMO the only reason to remove the cooler is if you're afraid of mechanical damage to it. FWIW I did have to change my factory cooler lines due to rust.

 

[Lubener]

That is a big vehicle and I would leave the cooler in place.

 

[Vitamin Yoda]

Should I disconnect the cooler or leave it in place?

The reason why GM and other manufacturers heat up the transmission fluid in their 1500 series trucks and SUVs us for fuel economy purposes. They're trying to get that ATF to around 5 cSt to minimize pumping and churning losses. All for an extra 0.001 MPG (not exaggerating). Ideally, these transmissions would be happiest with an ATF temperature range between 120F and 140F.

 

[spasm3]

I'd leave it. Its better for the trans.

 

[bullwinkle]

A lot of bigger GM trucks, vans, & SUVs have an external cooler even without having a towing package (my ex-rental ‘11 Express 3500 SWB is a good example, no factory hitch)-I would definitely leave it on, it will extend the ATF’s service life.

 

[joekingcorvette]

Leave it. The Corvette's with the Z-51 package have a better trans cooler or an auxillary one. As others have stated it's the high heat that will destroy a tranny.

 

[Snagglefoot]

2008 Chevy Suburban 1500, 4L60E. Installed a Tru Cool LPD transmission cooler in 2017 after buying an RV. Worked great.

We’ve now sold the RV, which means my original need for the cooler is gone. Temps rarely sniff GM’s stated operating range (around 190 I believe), even in summer. 165 is about it.

Should I disconnect the cooler or leave it in place?

Put another way, am I risking any issue by running ATF that is consistently below GM’s desired operating temp?

At what point would any moisture burn off? Fluid looks great on the dipstick and the truck, knock on wood, shifts fine at any temp.

Top of mind this weekend as I prepare for the usual 15k pan drain/refill…

We need some clarification. Did the truck originally have the transmission lines to the stock built in radiator cooler? And then you spliced in the auxiliary cooler? If you removed the auxiliary cooler, would you keep the lines attached to the radiator cooler. If the answers are yes, you can go ahead and remove the auxillary if you like.

However, it would probably help your transmission on hot summer days to leave it in. I have a factory auxiliary cooler that looks like a small radiator ahead of the main radiator. I stopped towing a long time ago and the transmission has 250,000 miles on it. All original.

 

[SHOZ]

The only time overcooling is really detrimental is if the fluid doesn't reach a high enough temp in a certain time frame on really cold days, the torque converter may not lock up. I saw this on a Taurus SHO I had with a big cooler. If it didn't reach 150F in 5 miles of highway driving or so it wouldn't lock up.

 

[4WD]

Tru Cool is designed to bypass a portion of the fluid when the cold ATF is thicker anyway … I’d keep it …
Also, if not towing you could extend that pan drain a bit longer …

 

[SHOZ]

Tru Cool is designed to bypass a portion of the fluid when the cold ATF is thicker anyway … I’d keep it …
Also, if not towing you could extend that pan drain a bit longer …

I use one of these as an oil cooler for the John Deere mower. I had it for years along with a oil temp gauge. Started using it in below 30F temps a couple years ago and it didn't have any oil pressure until the oil heated up enough to go though the tiny bypass orifice built into the bypass. Had to rig up a ball valve bypass for cold weather use.

 

[dnewton3]

Let's be more specific here ...
Keeping the fluid cool is for the sake of the fluid, not the trans. Yes; absolutely they are related, because if the fluid fails, then the trans will fail. So the heat is directly related to fluid life, but only indirectly related to tranny life.

Many of us have heard of the "50% fluid life reduction for every 10 degF of temp rise" lore, but that is based on the older fluids such as Dex IIIh and Mercon; those fluids sheard mightily and didn't take heat well at all. Newer fluid specs demand much better performance and content; they easily outlast their older counterparts. While the 4L60E was based on an older tranny design, by the time yours was made in 2008, it should have had Dex VI in it; a fairly capable fluid that is much more shear stable than its predecessor.

Further, in theory a fluid can be "too cool" for its designed application, though the ranges discussed in your post aren't dangerous by any means. This cold fluid condition will affect shift quality and shift speed; the latter also has an effect on wear of the clutches. For most applications, once the fluid is above 150F, it's "warm enough". This is kind of like the Goldilocks story; you don't want the fluid too cold or too hot - you want it in a range of acceptable (150F - 210F).

This topic is based on the following:
- lube choice (base stock and add-pack)
- expected max loads, and the frequency thereof
- OCI duration
- operating conditions (temps, speeds, etc)

Honestly, I doubt it matters much to the trans whether you remove it or not, if the other things are not pushing the envelope; it's going to affect your OCI more than the trans.

 

[HawkeyeScott]

Thanks, everyone. I appreciate the thoughts.

No original cooler if I recall correctly. Just plumbed this one in one weekend after pulling our new trailer for the first time and the tranny went to 215. Decided I’d better invest in a cooler. Again, it worked really, really well. Can’t sing its praises loud enough.

 

[PontiacHO]

Leave it. Not sure about your vehicle but newer models have the left bank exhaust pipe running directly under the transmission pan. Brilliant on GM for having a built in method to cook the transmission fluid.

 

[Snagglefoot]

Thanks, everyone. I appreciate the thoughts.

No original cooler if I recall correctly. Just plumbed this one in one weekend after pulling our new trailer for the first time and the tranny went to 215. Decided I’d better invest in a cooler. Again, it worked really, really well. Can’t sing its praises loud enough.

Just one more clarification. I’m pretty sure that truck had lines to the radiator from the factory. The “ factory cooler” was nothing more than a straight piece of pipe inside the rad, near the bottom. Next time you do a oil change, just check that your lines go to two connections near to bottom of the rad. I too have a 2008 Chevy Suburban, the only difference being mine is a 3/4 to with the factory auxiliary cooler. It still has the lines going to the rad.