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Discussion Starter #1
I tried searching the history for something similar, but couldn't locate anyone with the same issue . . .

I recently acquired a 2015 GMC Denali HD with about 85,000 miles on it. Since it had a gooseneck ball fitted, spent a majority of its life in the oil fields of West Texas, and no discernible history of transmission service, I decided to knock out a fresh fluid change, to include both filters. I captured all the fluid from the external filter, the drain plug, and the leftovers inside the pan/internal filter and it measured out to 9 (nine!) quarts of fluid. I used an actual 2-gallon graduated bucket from the hardware store and filled it to just below the brim. To note, I also confirmed that I have a stock pan and not a deep sump pan.

Prior to starting the process of changing the fluid, I did a cold check, followed by a hot check after running the truck around town for about 45 minutes. I didn't check the fluid temp, but assumed it be hot enough . . . more on that later. Both checks read about 1/2" below the respective hatched mark area at COLD (run for a minute, cycle between R,N, and D, and back to Park - engine running) and again at HOT.

After changing out both filters, cleaning the pan, etc., etc., etc., and since I only had two gallons of Transynd, I put about 7 quarts back in - with the intent of getting to 7.4 quarts slowly, which, to the best of my knowledge, is what I should expect to be putting in. I accomplished another COLD check and it was barely reading the dipstick. So, I put the rest of the gallon of fluid in and did another COLD check. Now, it's indicating a little over one inch below the COLD hatched mark area.

Next, I took the truck for a spin for about 15 minutes, but could only get the XSMN fluid temp up to roughly 140 degrees. I check it again and now it's reading about 1/2" below the COLD mark. I took the truck out again to try and get the temperature up to 160 degrees, but after running around for 45 minutes, and letting it idle for 15 minutes while I refueled, I could only get to just shy of 150 degrees. I let it sit for another 10 minutes and finally saw 155 degrees. I checked the level again and it hadn't changed at all from the 1/2" below the COLD mark.

Also to note, the test drives went flawlessly. The shifts were smooth and barely noticeable. Truck pulls strong. I even felt the shifting action between R, N, and D was much smoother than before as well.

So, after that exhaustive little synopsis of my morning - what do the internet experts think? Should I buy another gallon of Transynd and just keep adding fluid until it's finally within the respective COLD/HOT marks? Or just consult my inner FROZEN and just "let it go" and monitor accordingly?
 

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At 200, you should be at the top of the hot hash marks. At 175 you should be in the middle of the lower hot hash marks (bottom of hot hash marks when using the deep pan). Do a search for setting the level and brake standing the transmission. This will drive up the temperature in a controlled way and is OK to do if done correctly — like this:
—Set emergency.
—Trans in Drive with foot firmly on brake.
—Run 1000 RPM for 30-45 seconds.
—Trans in P/N and flush at 2000 RPM.
—Repeat this process a number of times and watch trans temp increase.
—Stop 5-10 degrees before 175 (temp will increase to 175 on its own)
—Check your level as per the manual instructs.
 
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Discussion Starter #4
Thanks enahs!
I had not heard of that of that procedure before. I bought another gallon of Transynd and added another quart a couple weeks ago. It reads about a quart low now which jives with what I initially drained.
I found somewhere that with dropping the pan and changing the internal filter that it should take 10 quarts to refill. (It was just a comment I breezed over, but haven’t found anything else since.)
That makes sense for what I drained out and thinking I was about a quart low prior to drain. I wish I would’ve had the foresight to capture a sample and send it off to Blackstone too, but it’s already contaminated with oil from my drain container.
 
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