I was at the dealer getting a recall for the passenger airbag done and they were pushing an auto trans service which is essentially a drain and fill.  But they were saying they do a relearn / reprogram of the trans when they do a the service.  Is there anything to this? 

The drain and fill really needs to be done 3 times, not just once, with short drives between drains, since about half the ATF stays in the torque converter, and won't drain out.

 

What is there to re-learn, or reprogram of the trans with simple fluid change?? I have no idea what is to be gained??

If you either haven't done any prior Trans service or don't know When it was last done, I don't recommend any kind of a Trans Flush on older Subie 4/5EAT's.* The flush will use force/power and could cause grief w/the internal seals. This somewhat debated online and here, but after experiencing it fir$t hand - $900 later (cheap rebuild)  - I won't ever do it again.

 

The 3x Drain, Refill, Drive is OK.

 

Most cars will do a 'relearn' after changing the ATF anyway...read your OM as it's likely described there.

 

 

*Your '05 could have either the 4EAT or 5EAT w/Sport Shift- depends on trim level/engine.

OM from '06 - should be same/similar to '05:

 

Section 7-12:

NOTE

-- Immediately after ATF (automatic
transmission fluid) is replaced, you
may feel that the automatic transmission
operation is somewhat unusual.
This results from invalidation of data
which the on-board computer has collected
and stored in memory to allow
the transmission to shift at the most
appropriate times for the current condition
of your vehicle. Optimized shifting
will be restored as the vehicle continues
to be driven for a while.

 

Tangent: -- When the engine coolant temperature

is still low, your vehicle’s automatic
transmission will up-shift at higher
engine speeds than when the coolant
temperature is sufficiently high in order
to shorten the warm-up time and
improve driveability. The gearshift timing
will automatically shift to the normal
timing after the engine has warmed
up.

Edited April 3, 20179 yr by wtdash

The flush will use force/power and could cause grief w/the internal seals. This somewhat debated online and here, but after experiencing it fir$t hand - $900 later (cheap rebuild)  - I won't ever do it again.

 

That depends on the type of flushing equipment used.  The machine we use has no pump, instead it has a tank with two bladders in it.  One of the bladders is filled with fresh fluid, the other left empty.  The machine is hooked inline with the cooler.  The car is started and, once the fluid has warmed up, the valve is switched from bypass to flush.  At this point, the old fluid goes into the empty bladder, forcing fluid out of the fresh fluid bladder back into the cooler lines.  Because the machine has no pump, the fluid pressure never exceeds the normal pressures for the transmission.  I wouldn't ever recommend forcing fluid through a transmission, that is asking for trouble.  Of course, the 3x drain and fill can work too, though for a shop, it is a little more time consuming.

 

That said, if a transmission is nearly shot, anything that forces it to have to relearn its shift adapts can cause it to fail completely.  This can even include a loss of power like changing or having to jump a battery.  Changing fluid also tends to fall into this, as the new fluid will have a different viscosity than the old worn fluid.  If the transmission was running at the edge of what it could compensate for, small changes could cause it to push over the edge, or simply not be able to get back to where they were from zero.

 

As to the original poster, the only Subarus I've seen that have any issues with the relearn are the CVTs, which you wouldn't have.  If your fluid is in bad shape, it might shift a little funny at first as wtdash said, but it should relearn it fairly quickly.  I've done several though with no noticeable difference in shifting.

 

If your fluid smells burnt though, new fluid won't fix burnt clutch-packs.

I am doing pure maintenance here before I send it down the road with my daughter.  I did 1 1x drain and fill so far .  Then I wait a week and do another mostly cause of my schedule.  That seems to do the trick.  I have not 3 drain and fills before. Conceptually, I get it, but just have never really done it.  Maybe I will try with this one.

 

I have never done the flush deal where they pump it out.

I was at the dealer getting a recall for the passenger airbag done and they were pushing an auto trans service which is essentially a drain and fill.  But they were saying they do a relearn / reprogram of the trans when they do a the service.  Is there anything to this? 

How many miles on the car?

152000

I got one of the hand-pumped vacuum-tank units and it makes this process so much easier...