Trans fluid fill while truck is cold?

Am I able to top off my trans fluid while the truck is cold/not running? Changed my rad the other day and lost a little bit. Trying to avoid getting burned. Thanks guys!!

 

There’s nothing stopping you, but the proper way to set/check the level of the 5-speed automatic A750 trans is to have it at the proper temperature to overflow out that hole to the proper fill level. Many threads on here telling how to do that.

 

Yup, after letting it get to temp and running thru gears then open overflow plug. Is there any particular reason it needs to be up to temp when being filled?

 

Yes. So you don’t over fill it.

 

Transmission fluid will expand when hot. If you do it while cold, you will most likely overfill the transmission.

 

Right. Will it not be the same after letting it heat up to proper(after filling before starting truck) temp before pulling the check plug?

 

You do you. It's not a forums general consensus to do it this way. It's Toyota's procedure to properly heat up, fill, cycle, and check the overflow and let out enough to not be overfilled.

 

If you fill up the exact amount that came out of the system. Having done the same thing, you don't lose a lot of ATF during a radiator replacement. I estimate about half a pint. But one good reason to do the proper fill procedure is so you don't assume it was set right to begin with. Many members have reported being under filled from the factory or a shop that did the job. If you don't have an ATF temp reader, I have tested my IR reader to being 1-3 degrees low with a reading at the pan. So, pull the plug at the lower end of temp range and you’ll be ok with an IR reading.

 

If I’m understanding you correctly, what you’re describing is the standard procedure. You don’t need to add fluid while the system is hot. Matter of fact you don’t want to because you’ll pass the correct temp and have to wait till it cools to level check. You just need to start the truck after you top off, work through the gears, get to temp, then drain until the liquid slows to a dribble.

 

Filling the transmission with the engine on has less to do with the temp and more to do with the fact that the torque converter holds 4-5 qts when the engine is running. When the engine is off it drains back into the pan

 

The drain and fill process described below drains and fills the transmission cold.

https://www.tacomaworld.com/threads/how-to-drain-refill-automatic-transmission.63851/

And when drained, about 3 quarts come out. I’ve done it three times, did it cold every time.

Doing it hot would suck. You’d likely run through the temp, have to wait for it to cool off and restart the vehicle. Not to mention touching hot surfaces as the OP mentioned.

 

The transmission doesn't have to be very hot to check it, the fluid check temperature is 95-115F unlike many others (like Ford and GM) that have to be at operating temp (190-210F).

You can fill it with the approximate amount cold before you start it then get it to the check temperature and remove the check plug (with the engine still running), if fluid runs out wait till it slows to a trickle and reinstall the plug. If fluid does not run out then add more until it does.