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ATF Level Thermal Expansion/Contraction Question
Finally concluding that checking the ATF level when HOT is too much of a moving target (who really knows if the TRANSMISSION is at operating temp?), I've decided it makes most sense to check the level when cold. Reason: I know that, when ATF is at "shop temperature" (68-86F), the correct level is approx. 1/2" below the minimum mark on the dipstick.
My question: if it's really cold outside, will the fluid level contract appreciably? Let's say is 20F outside, where would I expect correct level to be? Still at 1/2" below or significantly further down? Do these things behave in a linear fashion? FYI, I've got a leak I'm trying to keep a close eye on. Thanks.
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14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles 06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU 91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion 19 Honda CR-V EX 61k mi Fourteen other MB's owned and sold 1961 Very Tolerant Wife |
#2
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Quote:
Here's and idea Could it be the internal parts getting bigger as they heat up, taking up more room,( Increase in displacement.) increasing the fluid level? .
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[http://languageandgrammar.com/2008/01/14/youve-got-problems-not-issues/ ] "A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money." |
#3
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When I had my tranny pan off to to do the filter change, I looked at where the fluid dipstick ended up and where the fluid level inside the tranny must be. The fluid rises from just below the gasket when cold to just above the top edge of it when warm. The valve body sticks down into the pan though, so there's no real good way to estimate the volume around and inside it that is factoring into the level change. Moral to this story? Just measure it at 80C and be done with it
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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png Broadband: more lies faster. |
#4
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10mm below the add fluid mark when transmission is cold. Don't know about -20 question.
Drive the car for 20 to 30 minutes and the transmission is at temperature. Check the level and fill. Has worked for me on two different 124's. Level doesn't have to be exact. Now on my '97 S320 with the electronic transmission, level is critical. I have the special dipstick and an infrared thermometer. Steve |
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