Here is my experience with fluid change on the 7at:
I used Assenmacher ATF 180 adapter, fluid hand pump and IR thermometer of Amazon.
I dropped the oil pan and swapped it for another one that I bunged temp sensor and defi gauge into so I can monitor my tans temps at the track so that's how the fluid was drained. Then the mechanic filled it and drained it 3 times while the engine was off. I drove for awhile and noticed the car jerked when I came to stop from a hard braking. Obviously, the tranny was low on fluid because when it was filled the torque converter was at a standstill. We redid the procedure, however, this time the car was already at operating temp (fluid at 80-90C). Left the shop and still had the problem which indicated that I was still low on fluid. The third time I parked the car at the shop at night so it would cool down and started working on it the next morning. Turned it on, put it on the lift while running in neutral, pumped more fluid till it was full closed the fill port, monitored the pan temp with an infrared thermal gun of amazon till it reached about 35c that's when we reopened the fill and refilled it till it started dripping all while cycling through gears (5secs in each from P to D), when the fluid started to drip we closed the fill port.
What I learned:
*Trans fluid is affected a lot by temperature. I remember seeing a graph somewhere that showed the volume by the temp of the fluid. You should start after your car has cooled down.
*The car has to be relatively level.
*The cycle of filling and draining 3 times is mainly done to guarantee the fluid was completely changed everywhere in the tranny not only the fluid in the pan.
*Fluid temp in stock 7at almost matches the oil temp. I have 25-row Setrab 6 series on my car running with the stock in-radiator cooler and my fluid runs about 15-20c cooler than my engines oil temp. So at the track, I pull off when my oil temps are high and I don't have to worry about my trans fluid.
Sorry for the long read lol hope it helps
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