swathdiver
Full Access Member
I hear that about the K2 6L80s not the 8-speeds. Think I was told by someone on here that the 8L90s don't use that system either.
Transmission Temp - did I make a mistake?
- Thread starter Jhwhite05
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
Synthetic helps but I still subscribe to the notion that temps in a transmission are ideal between 160-175, regardless of anything else.
The trans could potentially "survive" one isolated incident like the OP describes assuming fluid is changed immediately and temps kept under 200* going forward but when the 6Ls overheat, the 4-5-6 is the first to burn.
Below is an example of what overheating does to the 6Ls , specifically...The 4-5-6 Drum/clutch. The pack on the left shows normal wear where temps were largely well-managed while the other one suffered several overheating events before being yanked.
That chart is often misrepresented as transmission life, but it’s actually fluid life in miles at each temp. And as you note, it’s for pre-Dexron VI fluid.
If it helps, in the February 2011 issue of Trailer Life magazine RV Clinic in response to a reader about the maximum transmission temperature allowed in a 2009 Chevy Silverado, the Tech Team had this response.
“General Motors’ in-house towing team expert provided RV Clinic with this statement: The maximum allowable automatic transmission fluid temperature is dictated by the transmission oil itself. The oil begins to degrade significantly above 270 degrees Fahrenheit, so we design vehicles so that in all but the most extreme conditions, the fluid temperature in the transmission sump stays below 270 degrees F.
We allow for up to 285 degrees F in extreme conditions (i.e. towing a trailer with combination loaded at GCWR in Death Valley). But for customer usage anywhere else in the country, even at GCWR, transmission sump temperature should stay well below 270 degrees F. Above this point, certain internal components, such as seals, begin to disintegrate rather quickly. Although newer synthetic fluids can withstand higher temperatures we still recommend this (270F) as a maximum temperature."
Finally, the GM orange manual (for RV chassis) says regarding Dexron VI ATF:
“300F is the maximum temperature. (Workhorse says 350F). This [converter outlet] is the normal place to install a temperature gauge or signal. The temperature in this location will vary significantly with each vehicle start-up or hill. If the temperature reaches 300F (350F), reduce throttle. To lower the transmission temperature with the transmission in NEUTRAL, run the engine at 1,200 RPM for 2-3 minutes to cool the oil. Do not allow the converter outlet temperature to exceed 300F (350F).
Keep a close check to prevent the engine cooling system from overheating.
300F would be typical of rocking the vehicle in mud, snow, or sand, or a transmission in stall (full throttle, no vehicle movement). When the transmission is in stall, the transmission will develop heat at a rate of one degree per second of stall.”
Last edited:
I tend to agree with the tranny guy, I'm much more comfortable at 180deg pan Temps, it will be higher at the pump and in the converter than the pan sensor. if it got that hot I'd change fluid as soon as I got home, personally I'm thinking of changing from acdelco dex6 to Amsoil before my next long tow into the mountains, even thou this is low mile fluid, never got over 167deg last time and fluid sample came back good. it just feels like cheap insurance and amsoil seems to be rated as a better fluid than factory stuff. one more change can hurt anything but my wallet haha
so yeah, I'd change fluid, full flush not just 3qt pan drop and work on mods to keep the Temps down for next time.
so yeah, I'd change fluid, full flush not just 3qt pan drop and work on mods to keep the Temps down for next time.
mikez71
Full Access Member
- Joined
- Mar 9, 2023
- Posts
- 1,369
- Reaction score
- 1,604
Is there an easy way to do a full flush?
I was thinking about sucking it out the dipstick tube to start, then doing a pan/filter a month or two later..
Or am I better off going to a lube shop?
I was thinking about sucking it out the dipstick tube to start, then doing a pan/filter a month or two later..
Or am I better off going to a lube shop?
OP
OP
Jhwhite05
Member
- Joined
- Sep 17, 2021
- Posts
- 42
- Reaction score
- 74
Thanks helpful, thank you. I’ll do that!
swathdiver
Full Access Member
Grumpy Bear over at GM-Trucks forum documented a 1 mpg increase when he switched his pickup's 6L80 over to Amsoil transmission fluid. Last time I checked, Amsoil was twice as expensive as ACDelco's Dexron VI. Just paid $145 for 4 gallons delivered of 10-9244.
Yes!
This is what you need or some semblance of it:
One Hayden 397:
One Lisle 22930:
At least 10 feet of 3/8" ID Clear Vinyl Tubing:
UDP 3/8 in. I.D. x 1/2 in. O.D. x 10 ft. Clear Vinyl Tubing T10006008 - The Home Depot
Everbilt clear vinyl tubing is BPA-free and manufactured using FDA approved food grade compliant materials. The crystal clear and non-toxic tubing is great for low pressure applications such as beverage
www.homedepot.com
One Bucket:
Set your parking brake and disconnect the upper transmission cooler line from the passenger side of the radiator using the Lisle 22930 tool. One hand to insert and twist and the other to pull ******* the line to release it. The line will not be used to exchange fluid and does not need to be covered.
Next, insert the Hayden 397 into the radiator until it clicks and then attach your tubing to it. It's a tight friction fit so you should not need to clamp it. Put the other end of the tubing into the bucket.
Start the engine and the transmission will begin pumping out the contents of the transmission pan. As soon as we see bubbles, we turn the motor off and add six quarts of new fluid through the dipstick. Then we start the engine again and pump out another 6 quarts or until we start to see the color of the fluid change for the better, bright red. Turn off the engine.
We then disconnect the Hayden 397 using the Lisle 22930 again and push the factory line back into the radiator. We add 4-5 quarts of fluid through the dipstick and start the engine. We move the gear shift lever through the gears, holding in each one for 5 Mississippi's then let it idle until the fluid gets to 90 degrees so we can check the level at the COLD check marks on the dipstick.
Once that's done, we take the truck for a spin around the neighborhood, trying to get the temperature to 160 degrees. This may require driving around in 2nd gear at 25-30 mph and we also make sure we get to 40-45 to make sure she naturally shifts through all the gears into 6th. Once the temp is up to 160 or more, we check the level on the HOT Check section of the stick and top her off as necessary.
It's a good time to take a sample and send off to Blackstone-Labs for analysis and take your Tech-2 and reset the internal Transmission Oil Life Monitor to 0%!
Oh, of course you need 12 quarts or 3 gallons of your favorite Dexron VI Full Synthetic fluid. We use 10-9244 or 88865618.
Oh goodness! The censors didn't like two words next to each other, h-a-r-d and o-n. Dirty mind that computer has.
OP
OP
Jhwhite05
Member
- Joined
- Sep 17, 2021
- Posts
- 42
- Reaction score
- 74
So much helpful information in this thread. Thanks to all for your contribution!
When I get home from this trip, I’m going to get a full flush.
When I get home from this trip, I’m going to get a full flush.
OP
OP
Jhwhite05
Member
- Joined
- Sep 17, 2021
- Posts
- 42
- Reaction score
- 74
My model didn’t come with a cooler, so I mounted one to the passenger side of the radiator.
Do you suspect the heat coming off the cooler/slightly blocking the radiator impacted the performance of the radiator and led to higher trans temps?
swathdiver
Full Access Member
Maybe, do you have a photo of the installation? If it's a big 40K cooler, when they are mounted in the stock location in front of the radiator, they wind up increasing the coolant temperature which in turn heats up the transmission fluid as it first passes through the radiator.
They guys on here have learned to mount them a little lower down, so their shed heat will not heat up the coolant in the radiator.
Similar threads
