How important is it to shift through gears right after ATF drain & fill?

[paulri]

I see instructions to shift from Park to 1/low gears and back again, after an ATF drain & fill. I'm going to do the Civic tomorrow, so I'm wondering if this is necessary. Since this is my own car, I'll be driving it all over the place in the next week, so the transmission will naturally be shifting into all the gears, including reverse. So why would I need to do this procedure immediately after a drain & fill?

FWIW, this is about 35K after my mechanic did a flush; the fluid is a dirty red (checked a few days ago).

 

[bdcardinal]

You do it to cycle the valves through all their motions to let the fluid get everywhere. Not doing so will give you a false reading.

 

[demarpaint]

It assures that the ATF is through the system, before it does any shifting. You can accurately determine the fluid level before driving or putting a load on the transmission. It is simple enough to do, I see no reason in the world not to.

 

[JeffKeryk]

As Nike sez, "Just do it."

 

[Gebo]

Yes, to give you an accurate fluid level reading. It will only take you 15 seconds. Well, maybe 30 seconds if you lose your concentration while in the process.

 

[dave1251]

It just helps I can not overstate this.

 

[Dan55]

I neglected to do it on 2000 Civic that had old Z1 and had shifting issues immediately after. They went away but might have been avoided by a gear change and battery disconnect .

 

[StevieC]

Today's transmissions can be quite finicky on proper fluid level. Even being over or under slightly is enough for some to start acting funny.
I'm not trying to install panic but it is something you are going to want to check properly.

 

[paulri]

OK you all talked me into it.

About how long do you folks leave the transmission in each gear? Just long enough to hear it shift?

 

[StevieC]

I like to put it in drive for 10 seconds, shift to neutral for a second and then into reverse for 10 seconds. I do this a couple of times and then put the vehicle in park or neutral (depending on how it wants to be checked) and then check the dipstick. Make sure it's a warm operating temperature idle and not a cold faster idle.

If a filter change was involved in the change be sure to double check the fluid level after a little bit of driving has occurred. Sometimes the media takes a good drive to fully saturate and it can modify the fluid level.
Not usually, but I have seen it in the past.

 

[bdcardinal]

Through each gear for a few seconds. Doesn't take long for the transmission to apply. P, R, N, D, S or however your transmission does anything after D.

 

[nthach]

I run through the gears for 3-4 seconds - the goal is to fill the valve body and the torque converter. After that, I do a "cold" check to make sure there's enough ATF to safely move the car. I then take it up to operating temp or the fluid check temp to do a "hot" check and top off as needed.

 

[69GTX]

I've done it both ways when hot and never noticed any obvious difference. Then again, I've never had a car newer than a 2002. I do dial it in using the proper method following a fluid change.

I also check my trans fluid dead cold/engine off several times over the course of a month and it's always on the same place on the dip stick, though at a significantly higher level....which means the exact same amount of fluid makes its way back the sump each time...and the same amount of fluid is spread among the rest of the transmission.

 

[Linctex]

A simple "drain and fill" won't change the fluid level very much ( you might see some change) prior to changing through the gears, of after......

However,
You *WILL* see a pretty big change in fluid level after a transmission rebuild, where everything internally is void of oil.

 

[DejaVue]

And of course there's less worry about getting the fluid refill level correct if you measure exactly how much you drain out then put exactly that much fluid back in.

 

[Garak]

Here's a thought. What about those guys who have a transmission you really can't select other gears? If I were to try with my G37, I can only choose PRND. To choose other gears, I have to go to sport mode, and then I can choose each gear on demand. However, sitting stationary, I would not be able to choose other forward gears, unlike, say, my 3 speed automatic LTD, which would have let me choose D21, and choosing 2 would actually put me in 2, and 1 would have put me in 1.

 

[StevieC]

Originally Posted by DejaVue
And of course there's less worry about getting the fluid refill level correct if you measure exactly how much you drain out then put exactly that much fluid back in.

Assuming it was correct to begin with and some of it hadn't evaporated which is normal to happen over longer OCI's in transmissions.

 

[stanlee]

First time I changed my auto tranny fluid I was a little low and it wouldn't even switch out of park. added more fluid and cycled it went into the gears but after a short test trip slipped. That was only about a half mile drive. Turned around and added more until I got a correct reading and not a single issue 30k miles later. DO IT! You need to do it first just to make sure its functioning and then you need to take a short drive to make sure its shifting properly and then you need to check the fluid again after driving while still warm to get an accurate fluid level.