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When I check my transmission with the motor running the dip stick indicates there is no transmission fluid but when I check the dip stick with the engine off the dip stick shows it to be full. I don get it!

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  • How are you meant to check the fluid level? some manufacturers require the engine running and cycled through the gears or after the engine has been switched off and waited for a few minutes etc etc Until you know the exact procedure for your car and transmission don't add any more. – Solar Mike Apr 25 '19 at 15:40
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In an automatic GM transmission of that era, you need to check the transmission fluid with the engine/tranny completely warmed up, on level ground, in neutral (parking brake applied), and the engine running. If it shows low, you need to add fluid. You DO NOT want to overfill the transmission, though. Add a little bit (1/2 a quart at most), then cycle the transmission through the gears slowly, ending back up in neutral. Pull the dipstick, wipe it off, restick, pull again and then check the level. If still low, add a little more and follow the same process. Overfilling an automatic transmission can be just as bad as it being under. It may cause seals to blow due to higher fluid pressures.

You need to check on/around your transmission for leaks and see if it is moist somewhere. If so, you don't want to keep running the transmission low on fluid. These transmissions are basically closed, meaning it doesn't use any fluid in the process of doing its business. If you find it low again after topping it off, you have an issue you need to have checked.

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  • When the engine is running the torque converter is filled with oil , that is the time to check fill level. When off , the oil runs out of the converter back into the sump and raises the level. – blacksmith37 Jan 15 at 16:11
  • @blacksmith37 - Some will drain out, but there's a bunch left in there. It could possibly at the most drain down to the inside bottom of the drive hub, but this doesn't mean it will. That leaves approx. 1/2 of the fluid left in the TC. Measuring the fluid while running is how GM engineers designed it to be done, partially for what you're talking about, but also because it drains back out of all the nooks/crannies within the transmission when the engine (and thus the pump) aren't running. Good insight, though! – Pᴀᴜʟsᴛᴇʀ2 Jan 15 at 16:17

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