Help a noob. What towing weight to start considering a transmission cooler?

TazzyTazzy · May 10

We just picked up 'Hank', our first pickup. He's a 2024 Silverado 3500 SRW with gas engine, L8T.

At what weight should we start considering a better transmission cooler? We are in Sacramento and sometimes have to climb out of the valley, such as the Sierra Nevada mountain range. Our travel trailer currently weighs just under 5000 pounds, at some point we will upgrade to something slightly larger.

Many times, we are towing in the summer when it's 100-105 (sometimes 108-110) degrees to escape the heat, such as north to the redwoods (still semi-mountainous), or the ocean.

We have 207 miles on it now, and the transmission runs around 155-170. We won't be towing until we have at least 1500 miles on Hank.

Second part of question: What transmission cooler is recommended for this? It appears most are marketed towards diesel versions. Is it the same fitment/parts?

Epsilon Plus · May 10

The stock cooling system is massive and more than adequate to pull max weight on the Davis Dam and Ike Gauntlet. At 5,000lbs I may not even use tow/haul on that.

Another JR · May 10

Another vote for “you don’t need it.”

Hank is the name my granddaughter gave our 4runner. She calls our 3500hd Frederick. Our camper is “Frederick’s backpack.”

64BAwagon · May 11

Never saw any trans temp issues with my 6 spd or my current 10 spd. I have towed over 8k miles with these 2 trucks. The 36ft fifth wheel and all our supplies weighs in around 13k.

I did wrap the exhaust pipe that crosses under the trans pan on my 2024 10spd. A few dollars worth of heat wrap seems to keep some of the exhaust heat from radiating into the trans pan. Even in stop and go traffic at 80 deg ambient the trans rarely got up to the 180's unlike some previous trucks I have owned these 2 came with some serious cooling. My 2005 LLY Duramax would have been on the side of the road puking where these 2 trucks weren't even breaking a sweat.

Strictly anecdotal and acknowledging that the 10 spd isnt a legit Allison design, I had an Allison tech at a very busy Allison authorized dealer tell me that anything within 10 degrees of the coolant temp was okay. Take that FWIW.

BCGM · May 11

64Awagon Could you explain that last paragraph to me a bit more .

What does within 10 Degrees of coolant temp mean ?

Also what wrap did you use on your exhaust under the transmission ?

Thank You

TazzyTazzy · May 11

20 hours ago, Epsilon Plus said:

The stock cooling system is massive....At 5,000lbs I may not even use tow/haul on that.

Thanks for the feedback. It's appreciated and good tip about the tow haul mode. I'll just use this will climbing/descending steep portions of mountains.

TazzyTazzy · May 11

7 hours ago, 64BAwagon said:

I did wrap the exhaust pipe that crosses under the trans pan on my 2024 10spd. A few dollars worth of heat wrap seems to keep some of the exhaust heat from radiating into the trans pan.

Awesome. Thanks for the data point. We won't be doing anything then.

Any chance you can post a pic or explain where/how you mounted the heat shield? Something passive that can help is perfect.

64BAwagon · May 11

It was simple exhaust wrap 2" wide. I did the pipe about 2 ft where it goes under the trans pan. The hardest part is keeping the wrap tight. It typically comes with a few metal zip ties to secure it.

https://www.designengineering.com/titanium-exhaust-wrap-2-x-15/

Edited May 11 by 64BAwagon

64BAwagon · May 11

3 hours ago, BCGM said:

64Awagon Could you explain that last paragraph to me a bit more .

What does within 10 Degrees of coolant temp mean ?

Also what wrap did you use on your exhaust under the transmission ?

Thank You

Meaning if your coolant temp is 200 and the trans temp is within 10 degrees either side of that then youre okay. If you coolant was 200 and your trans was 230 then its not controlling the trans temp well enough. On both my 2021 6L90 and my 2024 10L1000 the trans temp has never gotten within 10 degrees lower than the coolant temp.

I will say that with the Scangage3 I am monitoring oil temp and I am surprised that with a load on the truck and after its driven for a while the oil temp will get above the coolant temp. It seems to run around 10-20 degrees above coolant temp. For me its a solid argument for using the quality oil like the Dexos1, Gen3 that GM calls out for the gas engine.

BCGM · May 12

23 hours ago, 64BAwagon said:

Meaning if your coolant temp is 200 and the trans temp is within 10 degrees either side of that then youre okay. If you coolant was 200 and your trans was 230 then its not controlling the trans temp well enough. On both my 2021 6L90 and my 2024 10L1000 the trans temp has never gotten within 10 degrees lower than the coolant temp.

I will say that with the Scangage3 I am monitoring oil temp and I am surprised that with a load on the truck and after its driven for a while the oil temp will get above the coolant temp. It seems to run around 10-20 degrees above coolant temp. For me its a solid argument for using the quality oil like the Dexos1, Gen3 that GM calls out for the gas engine.

My apologies 64BAwagon . I' m not very mechanically inclined . I think I need to research how the cooler works for the transmission as I think that is what you are pointing to ? Bear with me here . Coolant in the transmission cooler is what you are talking about ? That is what keeps the transmission cool ? I need to understand this topic

Edited May 12 by BCGM

newdude · May 12

On 5/10/2024 at 6:01 PM, TazzyTazzy said:

We just picked up 'Hank', our first pickup. He's a 2024 Silverado 3500 SRW with gas engine, L8T.

At what weight should we start considering a better transmission cooler? We are in Sacramento and sometimes have to climb out of the valley, such as the Sierra Nevada mountain range. Our travel trailer currently weighs just under 5000 pounds, at some point we will upgrade to something slightly larger.

Many times, we are towing in the summer when it's 100-105 (sometimes 108-110) degrees to escape the heat, such as north to the redwoods (still semi-mountainous), or the ocean.

We have 207 miles on it now, and the transmission runs around 155-170. We won't be towing until we have at least 1500 miles on Hank.

Second part of question: What transmission cooler is recommended for this? It appears most are marketed towards diesel versions. Is it the same fitment/parts?

Stock system should be more than enough where you are now. I'd say that frequent transmission fluid change intervals would be most important with your ambient temps as the transmission will likely hit 190-210F, even if you added a larger aux cooler. This is due to the 10L1000 having a thermal bypass valve inside the valve body. It begins to open at 143F. I'd say at least a pan drop to replace most of the fluid every 30,000mi would be beneficial.

10L holds a lot of fluid too (which is good as it should take that amount to warm up a bit longer). Total system is 22.08 quarts, and 14.37qts of that is replaced during a pan drop.

2 hours ago, BCGM said:

My apologies 64BAwagon . I' m not very mechanically inclined . I think I need to research how the cooler works for the transmission as I think that is what you are pointing to ? Bear with me here . Coolant in the transmission cooler is what you are talking about ? That is what keeps the transmission cool ? I need to understand this topic

Here's the cooler lines for the 10L1000 with the 6.6 Gas. Once the TBV is opened or starts to open (143F), ATF will flow from the transmission to the fitting at the bottom of the LH radiator tank (callout #13 with the line down). ATF will then come out the top fitting (callout #13 line pointing up) and into the short pipe (callout #15) and then through the auxiliary cooler (callout #1). From the aux, it will the flow back to the transmission.

So when up and running for a bit, and the TBV is wide open, the transmission should run within 10-20 degrees of engine coolant temperature because the ATF flows first through that left tank on the radiator. The Aux cooler being mounted ahead of the radiator (and probably the condenser) allows that fluid to cool to that 10-20 degree window below water temp.

Pryme · May 13

12 hours ago, newdude said:

Stock system should be more than enough where you are now. I'd say that frequent transmission fluid change intervals would be most important with your ambient temps as the transmission will likely hit 190-210F, even if you added a larger aux cooler. This is due to the 10L1000 having a thermal bypass valve inside the valve body. It begins to open at 143F. I'd say at least a pan drop to replace most of the fluid every 30,000mi would be beneficial.

10L holds a lot of fluid too (which is good as it should take that amount to warm up a bit longer). Total system is 22.08 quarts, and 14.37qts of that is replaced during a pan drop.

Here's the cooler lines for the 10L1000 with the 6.6 Gas. Once the TBV is opened or starts to open (143F), ATF will flow from the transmission to the fitting at the bottom of the LH radiator tank (callout #13 with the line down). ATF will then come out the top fitting (callout #13 line pointing up) and into the short pipe (callout #15) and then through the auxiliary cooler (callout #1). From the aux, it will the flow back to the transmission.

So when up and running for a bit, and the TBV is wide open, the transmission should run within 10-20 degrees of engine coolant temperature because the ATF flows first through that left tank on the radiator. The Aux cooler being mounted ahead of the radiator (and probably the condenser) allows that fluid to cool to that 10-20 degree window below water temp.

Always comes in with amazing content and pics for everything. Thanks!

64BAwagon · May 13

@BCGM I was referring to the two temps as a comparative, not that they are linked physically. The transmission cooler is part of the fluid system in the transmission only.

Scott

Edited May 13 by 64BAwagon

BCGM · May 13

19 hours ago, newdude said:

Stock system should be more than enough where you are now. I'd say that frequent transmission fluid change intervals would be most important with your ambient temps as the transmission will likely hit 190-210F, even if you added a larger aux cooler. This is due to the 10L1000 having a thermal bypass valve inside the valve body. It begins to open at 143F. I'd say at least a pan drop to replace most of the fluid every 30,000mi would be beneficial.

10L holds a lot of fluid too (which is good as it should take that amount to warm up a bit longer). Total system is 22.08 quarts, and 14.37qts of that is replaced during a pan drop.

Here's the cooler lines for the 10L1000 with the 6.6 Gas. Once the TBV is opened or starts to open (143F), ATF will flow from the transmission to the fitting at the bottom of the LH radiator tank (callout #13 with the line down). ATF will then come out the top fitting (callout #13 line pointing up) and into the short pipe (callout #15) and then through the auxiliary cooler (callout #1). From the aux, it will the flow back to the transmission.

So when up and running for a bit, and the TBV is wide open, the transmission should run within 10-20 degrees of engine coolant temperature because the ATF flows first through that left tank on the radiator. The Aux cooler being mounted ahead of the radiator (and probably the condenser) allows that fluid to cool to that 10-20 degree window below water temp.

NewDude Thank you so much for the graphic and explanation ! I will post my take on what you have provided in hopes that I have got it !

Edited May 13 by BCGM

BCGM · May 13

4 hours ago, 64BAwagon said:

@BCGM I was referring to the two temps as a comparative, not that they are linked physically. The transmission cooler is part of the fluid system in the transmission only.

Scott

Scott Thank You !