Transmission Cooler AND Engine Oil Cooler?

[BadgerRoo]

Hi all!

Long time reader first time poster:

I have a 2012 GMC Yukon XL 1500 with the tow package but without the K5L HD trailering package. Basically, I have the 5.3L 3.08 rear axle with no transmission or engine oil cooler. As I'm sure some of you know, this puts me at a whopping 5,000 lbs trailering capacity (11,000 GCVW) and I can get up to 5,500 lbs trailering capacity with a WDH which I do have. I tow a 2014 Roo dry at ~3,850 lbs and try to be as minimalist as possible with cargo. Towing my Roo a month ago in the balmy 15 degrees F that is Wisconsin, I noticed my transmission temp hanging in the 150-170 range. This is concerning to me as I've read GM's typically "run hot" and if this is the temp I am getting with the ambient temp being 15 degrees F, what am I to expect when it's 85 degrees and humid with the A/C running?

Anyhoo.. if I had the 3.42 rear axle, my manual says I would only increase my trailering capacity by 500 lbs. HOWEVER, if I had the K5L cooling package with the 3.42 rear axle, I could tow 8,000 lbs and my GCVW would be 14,000 lbs.

So, I did a little research and found the K5L cooling system basically comes down to having a transmission cooler as well as an engine oil cooler. I don't plan on spending the ~$1,500 to have the rear axle switched out (especially since the manual states going from a 3.08 to a 3.42 only adds 500 lbs towing and does not change the 11,000 GCVW), but adding the coolers seems to be what really improves overall performance towing.

My questions are, in my case..

1) How important is it that I get these coolers installed? I don't go too far but every summer there is usually a trip or two that is 2 - 3 hours away.

2) How important is an engine oil cooler? Would I be fine with only getting the transmission cooler? Or do you all recommend both?

3) So if I have both the transmission cooler and engine oil cooler installed but stick with the 3.08 rear axle, would the math still work out; that I would maybe have 7,500 lbs towing capacity since my manual states increasing from a 3.08 axle to a 3.42 only gives me 500 lbs more trailering capacity? Or does it not "work like that" with trailering?


Thank you all for your time and sorry for the novel!!!

[Todouble]

You may be fine. I run170-175 tranny in the winter, on hot summer days 200-210. Pulling a steep grade a little higher than
That. I wouldn't worry yet you may be fine. Just keep an eye on it and don't let it get away from ya .

[jtstromsburg]

After paying for a new transmission in my old suburban, I added a cooler (burned the old tranny towing a buddies pickup to a shop, which is another story). I feel the cost of the coolers is worth it, and would still pay close attention to your temps. I think the gauges are as important as the cooler, but be prepared to pull over and shut down as needed. I sold the burb and bought a 3/4t truck. It sounds like you have plenty of truck for your current rig, but think about the cost of mods to the Yukon vs cost of a truck made for pulling, IF you think you may upgrade campers in the next couple years. Like I said, just watch your temps and you should be fine

Sent by me

[checca]

1. Get the largest plate and fin transmission cooler you can fit in front of you a/c condenser.

2. Get an oil cooler, but doesn't have to be the largest ... Just make it fit.

My 1998 mistsubshi montero sport has over 70,000 miles towing an 8000 lbs enclosed trailer, it now has over 239,000 miles and going strong. When I got it, my mechanic told me to do the above ... Along with a year transmission flush. Still have all the original parts and going strong.

[TURBS]

Imo here's what I would do given your situation.

I have an abundance of late model salvage yards in my area and I'd go find a like yukon with the cooler packages and remove them to be installed on my unit.

I believe you could even remove them from a like year 1500 pick-up.

With that said you already have a trans cooler the is inside your radiator and the hd cooler package runs another auxiliary cooler out in fron of your a/c condenser which is still tied into radiator cooler.

The engine oil cooler ports are already on your engine on the left side by your oil filter and plugged.

Last thing.
You mentioned the possibility of changing out your rear diff but is your yukon not a 4x4?
If so you'd need to replace the front and the rear diffs.

Just my opinion.

Good luck.

TURBS

Think spring!
The last man standing also has a sharpie

[Batts-toy]

What is the temperature of the tranny when not towing the TT. I think it will be higher than you expect. Some (actually a lot) of vehicles route the tranny lines through a small tank in the radiator to purposely heat the tranny fluid then if the tranny temp goes higher than the radiator coolant it will remove heat.
So the tranny fluid is seeing 180 to 220 temp in the coolant depending on the vehicles coolant temp. control point thermostat.

Welcome to the forum from mid California.

[BadgerRoo]

Thanks all for your responses! Learning a lot!

jtstromsburg - I feel the transmission temp that I can monitor from my DIC is fairly accurate.. would you still recommend an aftermarket gauge as well? Don't want to go overboard too seriously here, but I have no idea if the factory gauge on my DIC is known for being inaccurate or if it's pretty spot-on?

f1100turbo - You're right, I do have the 4X4 and would have to change out both axles.. since we plan on holding onto this new unit until the kids are much older/bigger, that's not gonna happen.. lol. But I am hoping that the coolers make all the difference since my manual states a 3.08 to a 3.42 is only good for an extra 500 lbs. towing anyway.. not worth it IMO.

And I'm not blessed with many salvage yards in my area let-alone late-model yards, and I hear the factory GM cooling systems are frequently swapped out (or at least supplemented) with aftermarket ones anyway, so I think I'll stick with the aftermarket route but thanks for the idea!

checca - Not to sound ignorant or anything, but you're towing a 7,000 lbs unit with a mid-size V6? Holy Cow! Good for you! Do you get the transmission flush every year or the fluid replacement? (I've read there's a difference)

Batts-toy - I actually just watched my transmission gauge on the way home the other day going 55-60 MPH on a flat highway for about an hour drive.. I was anywhere from 90-120 degrees F. So, towing at 150-170 degrees F in similar weather seems like too big of a jump for comfort; am I wrong here? Honestly, I have no clue..


**I also think I should mention that I do love my truck and it fits our family's needs beautifully.. the only possible hiccup is the trailering I do 5 - 8 times a year, which is not enough to upgrade (at this point of our lives) to a 3/4 ton. I guess I'm asking for answers with the TV I have now as I do feel, as it sits right now, that I have enough truck for what I'm towing; I just like to be conservative and extra-cautious.

[Batts-toy]

Originally Posted by BadgerRoo

Thanks all for your responses! Learning a lot!

jtstromsburg - I feel the transmission temp that I can monitor from my DIC is fairly accurate.. would you still recommend an aftermarket gauge as well? Don't want to go overboard too seriously here, but I have no idea if the factory gauge on my DIC is known for being inaccurate or if it's pretty spot-on?

f1100turbo - You're right, I do have the 4X4 and would have to change out both axles.. since we plan on holding onto this new unit until the kids are much older/bigger, that's not gonna happen.. lol. But I am hoping that the coolers make all the difference since my manual states a 3.08 to a 3.42 is only good for an extra 500 lbs. towing anyway.. not worth it IMO.

And I'm not blessed with many salvage yards in my area let-alone late-model yards, and I hear the factory GM cooling systems are frequently swapped out (or at least supplemented) with aftermarket ones anyway, so I think I'll stick with the aftermarket route but thanks for the idea!

checca - Not to sound ignorant or anything, but you're towing a 7,000 lbs unit with a mid-size V6? Holy Cow! Good for you! Do you get the transmission flush every year or the fluid replacement? (I've read there's a difference)

Batts-toy - I actually just watched my transmission gauge on the way home the other day going 55-60 MPH on a flat highway for about an hour drive.. I was anywhere from 90-120 degrees F. So, towing at 150-170 degrees F in similar weather seems like too big of a jump for comfort; am I wrong here? Honestly, I have no clue..


**I also think I should mention that I do love my truck and it fits our family's needs beautifully.. the only possible hiccup is the trailering I do 5 - 8 times a year, which is not enough to upgrade (at this point of our lives) to a 3/4 ton. I guess I'm asking for answers with the TV I have now as I do feel, as it sits right now, that I have enough truck for what I'm towing; I just like to be conservative and extra-cautious.

Better safe than sorry, I would hit the salvage yard and get one installed. Auto parts store sell universal cooler kits is another option.

[BadgerRoo]

Originally Posted by Batts-toy

Better safe than sorry, I would hit the salvage yard and get one installed. Auto parts store sell universal cooler kits is another option.

By one installed are you talking I should be fine with just the transmission cooler or should I go ahead with the engine oil cooler too right off the bat? Don't mind being cautious but don't want to spend more than I have to either.

[Mtelkman]

Trans coolers are pretty cheap insurance. Change the fluid while you are at it.

I usually agree with f1100turbo but I will STRONGLY caution you not to go get a trans cooler from a wrecking yard. You want a new cooler simply because you cannot guarantee what shape the trans was in on the donor vehicle. It could have some metal shavings or grime in it that could get into your existing transmission. Trans coolers are notoriously difficult to clean.

I would hold off on the engine oil cooler until you can further assess the engine temps and see what they do. Also I wouldn't bother changing axle ratios. If you get to the point where you need them changed in order to tow, it is likely a better idea to get a different tow vehicle.

[Batts-toy]

Originally Posted by BadgerRoo

By one installed are you talking I should be fine with just the transmission cooler or should I go ahead with the engine oil cooler too right off the bat? Don't mind being cautious but don't want to spend more than I have to either.

With the size TT you have, personally I would only do the Tranny cooler. As long as your engine temp stays in the normal range I wouldn't worry about having the oil cooler unless you plan to do a lot of mountain climbing where your engine RPM's run high a lot.

[beerjay]

I was in the same situation with my Suburban last spring when I bought the TT (3.42 rear). It is 5400 lb without cooler and 7900 lb with cooler.

The Suburban did not have the aux trans cooler (checked the build sheet with dealer). The trans fluid goes through the existing rad to warm it up initially then does a moderate job of cooling. You will find it will get really hot when the weather warms up.

I had GM put trans oil cooler in (not the GM build one but an OEM one). I towed 4000 km last summer down east up some big hills in 90+ degree weather at 3000+ rpm with AC on. My DIC never went above 200-210 F. At 265F the engine computer will slow you down and warn you to pull over to avoid damaging the trans and burning the fluid.

Have not had a need for an oil cooler.

My cousin is a mechanic, and he said to flush the transmission yearly since driving in the winter without towing does not push the fluid through the aux cooler with enough force, so it may clog up and cause problems in the summer when towing. Don't get a used cooler.

[SKnight]

For the trans, I'd get an aftermarket cooler to help with the trans, install it on the return line from the radiator to the trans so that the coolest fluid goes to the trans. Flowing through the radiator heats it up to near engine temps but as stated, cools it down under a load.

Hayden PN 405 is a good option. I'm a rep for Hayden coolers, so if you have a cooler question I should be able to help.

As for oil, I'd see about getting the factory lines from a wrecking yard, then plumb in a new cooler. Best of both worlds there. A power steering cooler is a good option too.

[BiigDaddy]

Originally Posted by jtstromsburg

I feel the cost of the coolers is worth it, and would still pay close attention to your temps. I think the gauges are as important as the cooler, but be prepared to pull over and shut down as needed.
Sent by me

If you do experience higher temps, you would definitely want to pull over, but DO NOT shut the engine down. Let it run to circulate the fluid through the coolers until the temps drop, as shutting it down has the potential for overheated fluid to sit and cook... Welcome to the forum!

[checca]

Originally Posted by BadgerRoo

Thanks all for your responses! Learning a lot!


checca - Not to sound ignorant or anything, but you're towing a 7,000 lbs unit with a mid-size V6? Holy Cow! Good for you! Do you get the transmission flush every year or the fluid replacement?

**I also think I should mention that I do love my truck and it fits our family's needs beautifully.. the only possible hiccup is the trailering I do 5 - 8 times a year, which is not enough to upgrade (at this point of our lives) to a 3/4 ton. I guess I'm asking for answers with the TV I have now as I do feel, as it sits right now, that I have enough truck for what I'm towing; I just like to be conservative and extra-cautious.

I got a flush every year, the local oil change place has this machine Clore TT500 T-TECH Express ATF Exchange System

It's passive so you didn't need to worry about them overfilling or over pressuring the transmission. I also got normal filter changes at 100,000 miles. Your had to be conservative when towing, never went over 65mph. But I've towed all in the Midwest and foothills out east.

[BadgerRoo]

Originally Posted by beerjay

I was in the same situation with my Suburban last spring when I bought the TT (3.42 rear). It is 5400 lb without cooler and 7900 lb with cooler.

The Suburban did not have the aux trans cooler (checked the build sheet with dealer). The trans fluid goes through the existing rad to warm it up initially then does a moderate job of cooling. You will find it will get really hot when the weather warms up.

I had GM put trans oil cooler in (not the GM build one but an OEM one). I towed 4000 km last summer down east up some big hills in 90+ degree weather at 3000+ rpm with AC on. My DIC never went above 200-210 F. At 265F the engine computer will slow you down and warn you to pull over to avoid damaging the trans and burning the fluid.

Have not had a need for an oil cooler.

My cousin is a mechanic, and he said to flush the transmission yearly since driving in the winter without towing does not push the fluid through the aux cooler with enough force, so it may clog up and cause problems in the summer when towing. Don't get a used cooler.

Thanks for the advice! Do you flush your tranny before or after the winter then?

[BadgerRoo]

Originally Posted by SKnight

For the trans, I'd get an aftermarket cooler to help with the trans, install it on the return line from the radiator to the trans so that the coolest fluid goes to the trans. Flowing through the radiator heats it up to near engine temps but as stated, cools it down under a load.

Hayden PN 405 is a good option. I'm a rep for Hayden coolers, so if you have a cooler question I should be able to help.

As for oil, I'd see about getting the factory lines from a wrecking yard, then plumb in a new cooler. Best of both worlds there. A power steering cooler is a good option too.

You reccommend the older tube and fin type coolers over the newer and supposedly more efficient designs?

[checca]

I flushed every fall, once the trailer went into winter storage.

[Sgt. Schultz]

Sounds like you would like to keep the Yukon for a while so both coolers are IMHO very good insurance - something from TRANSMISSION COOLERS | B&M Transmission Coolers - lightweight all-aluminum construction -- in addition good quality fluids (I prefer synthetic) changed at a regular interval.
Check with a good transmission shop you may need to beef up the RAD fans to move enough air with the additional coolers. I would look at a finned differential cover for the rear Mag-Hytec Performance Differential Covers - Truck Customizers if you find you are running near max capacity - look at changing the diff fluid every couple of years

[beerjay]

Originally Posted by BadgerRoo

Thanks for the advice! Do you flush your tranny before or after the winter then?

My cousin recommended after the winter. The winter driving does not get up to the same RPMs as towing the trailer so there may be some buildup in the trans cooler.

I still can't believe the trans cooler didn't come with the HD trailer package on the Suburban. Has battery, cooling, alternator, suspension, Class 4 hitch upgrades etc.