Is it necessary to warm up the transmission fluid before doing a drain, or is it recommended for some reason? I'm not terribly concerned with getting every last drop out as a good portion will remain inside the transmission anyways.
Warm up transmission fluid before drain?
- Thread starter 92saturnsl2
- Start date
If you're referring to a pan drop honestly I don't think it matters that much. I usually drive it a few minutes and get the vehicle up nice and level on 4 ramps or jackstands. The temperature is usually below 100F. I let the transmission drain at least an hour with the pan down and close the garage door so no crap blows in from outside.
I've never done them hot. Nothing worse than a face full of scalding hot transmission fluid.
If your Tranny pan has a drain plug that heating it up is my preference.
However if you need to unbolt the whole pan and then let the fluid pour out of the one side of the pain first and let it drain, you don't want hot fluid possibly burning you.
However if you need to unbolt the whole pan and then let the fluid pour out of the one side of the pain first and let it drain, you don't want hot fluid possibly burning you.
DO NOT heat it up as it expands and unless the fluid going in is at the exact same temperature and therefore the exact same volume, you'll get false readings. When cold, both fluids are at the same temperature so you can do so many quarts out and an equal amount of quarts in.
Oil solubility goes up as it gets warmer. It can hold and thus drain more contaminants when warm.
I don't think with an automatic transmission it will matter too much. Reason being once you start the car and move it the fluid is circulating and what's not caught up in the filter and magnet in the pan is suspended in the fluid. There's still a large percent of fluid in the torque converter which is not getting drained with dropping the pan. So to do a thorough job, after the filter and pan have been reinstalled and the transmission topped up, driven and checked for leaks, a line off fluid exchange should get most of the remaining fluid and contaminants out.
OTOH changing engine oil warm is a good idea.
So then, do you recommend warm or hot drain? Thanks.
AutoMechanic
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I’ve never done it hot always cold.
Manual, yes.
Auto, no.
Auto, no.
I do it warm usually, just because the customer drives his car over and the fluid is warm. If the system is clean, oil solubility isn't a factor imo.
If at all possible, I flush AT until clean fluid comes out. Not possible if there's a filter in the pan to be changed of course.
doesn't matter, fill to cold level, go for a drive and recheck/add what's missing.
That's a PITA on a transmission with no dipstick. When I do a DAF....I'm only going through the check procedure once. So a cold fluid drain it is for me.
I'd rather do it cold
When it's cold, you can drain, measure how much you drained, and refill with the same amount.
When it's cold, you can drain, measure how much you drained, and refill with the same amount.
