Mosey
Well-known member
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- #1
Yesterday I went through the incredible hassle of checking my tranny fluid level. I used ForScan to get fluid temps and measured the level at 96C. I was OK and I added some fluid to bring the level to exactly the 3 mark as I have a 10R80MHT. Ford specs for that transmission say the level should be between 3 and 4 so I was right at the high end of the range and all is good.
This morning I decided to do a little test and take a measurement when cold. The temperature when I started the truck as 48F, 9C. I had the transfer case in 4L so that the engine would not turn off. I started the truck and then put the transmission in reverse of 5 seconds and then drive for 5 seconds - twice. I hopped under my truck and took the first measurement and almost crapped my pants, no fluid on the stick, none, zilch, zero. HOLY CRAP.
I knew there was fluid in the transmission and it went into reverse and drive without issue. So I patiently let the engine run and repeatedly took measurements. It took what felt like five minutes for the end of the dipstick to show the first signs of fluid. I continued checking for about another five minutes and the level climbed up to the 5 mark. I started up ForScan and took a quick temp reading of the fluid, about 55C and I noted that transmission temp gauge was almost to the little tick mark, about 1/4 range. I decided to brake torque to get the temp up to 96C and took another reading, this time it read 1/2 way between 3 and 4.
To say I was astonished is an understatement. I found the coefficient of thermal expansion values of hydraulic oil, 0.07% per degree celsius, and given a capacity of roughly 12 liters, or 12.9 quarts, it should expand approximately 1 liter in volume. It sure did. In closing, Ford is absolutely correct in stating that the fluid level must be measured HOT.
This morning I decided to do a little test and take a measurement when cold. The temperature when I started the truck as 48F, 9C. I had the transfer case in 4L so that the engine would not turn off. I started the truck and then put the transmission in reverse of 5 seconds and then drive for 5 seconds - twice. I hopped under my truck and took the first measurement and almost crapped my pants, no fluid on the stick, none, zilch, zero. HOLY CRAP.
I knew there was fluid in the transmission and it went into reverse and drive without issue. So I patiently let the engine run and repeatedly took measurements. It took what felt like five minutes for the end of the dipstick to show the first signs of fluid. I continued checking for about another five minutes and the level climbed up to the 5 mark. I started up ForScan and took a quick temp reading of the fluid, about 55C and I noted that transmission temp gauge was almost to the little tick mark, about 1/4 range. I decided to brake torque to get the temp up to 96C and took another reading, this time it read 1/2 way between 3 and 4.
To say I was astonished is an understatement. I found the coefficient of thermal expansion values of hydraulic oil, 0.07% per degree celsius, and given a capacity of roughly 12 liters, or 12.9 quarts, it should expand approximately 1 liter in volume. It sure did. In closing, Ford is absolutely correct in stating that the fluid level must be measured HOT.
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