WRX Cold Weather Transmission Slip

[Edward Elhauge]

I have a 2002 WRX wagon with the 4EAT automatic transmission.

The problem I have is only during cold weather (32 deg F)
after sitting all night. I'll take off from my drive way
in the morning, going uphill, and try to accelerate hard
to match the speed of possible traffic on a rural highway.

The car engine sounds like it's spinning fast, and the tach
shows the RPM rising past 4000. Meanwhile the car is slowly
accelerating to about 10 to 15 mph. Scary, the way people drive
on that road.

Eventually, after driving 10 minutes or so the problem goes
away. This doesn't happen on warm days.

I was thinking that the problem was in the torque converter
linkage. I would think that the gearing itself would make
some sort of grinding sound if the gears were only partially
meshing. What do people think? I have 90000 mi on the WRX
and would love to find something for the dealer to fix
NOW, before the warranty runs out at 100000 mi.

I found the following post on a 4x4 list and wondered if
I could be experiencing something like this:

Hi. I am hoping someone can offer some help on my problem. I have a
1996 Ford F-150 truck with an automatic transmission. For the first 5
minutes after cranking my truck, the transmission slips (I guess that
is what it is
called). If I pull away from a stop sign, it will rev up some before
"catching" and going. The fluid level seems OK. This only happens
when it
is cold outside 30 - 40 degrees. It did it last winter a few times
also. The truck has 185,000 miles on it. Any ideas?

Slipping when it is cold often means that the line pressure is lower
than it should be and that can be a result of fluid which is too viscous
or has not been changed recently, plugged filter, dirty valve body
parts, deteriorated rings or seals, and a worn pump.

When I took some transmission classes years ago, the instructor said
always suspect the front pump when this sort of behavior was noticed.
But, as Steve posted, other things can affect it too.

Have you serviced it recently? A service and adjust (if it is one that
has adjustable bands) might be money well spent.

 

[Ratatooie]

Check your transmission fluid level. They are hard to fill right. (Do it
several days in a row and you might find one day it is down a little.)

Sit in your driveway a minute or two with the engine running to get a little
warmth in there or get a heater to plug the car in.

What you describe is more severe than my car is, but pretty much the same.
(It delays shifting unless you are really pounding on it to go, after a
block or two, it goes away.)

I assume that due to your driveway and road you can't just mope a long a
block or two, but if you can alter your route to go slower at first it might
help.

 

[MN]

This issue has been discussed before.

The solution seems to be better engine warm up.

Let the car idle for 10 minutes or so, whatever is needed
to nicely warm up the engine before taking-off. Apparently
a warmer engine positively affects the transmission (helps
it warm up faster also, I guess). Anyway, shifting problems
on take-off may be greatly diminished.

MN

Check your transmission fluid level. They are hard to fill right. (Do it
several days in a row and you might find one day it is down a little.)

Sit in your driveway a minute or two with the engine running to get a
little warmth in there or get a heater to plug the car in.

What you describe is more severe than my car is, but pretty much the same.
(It delays shifting unless you are really pounding on it to go, after a
block or two, it goes away.)

I assume that due to your driveway and road you can't just mope a long a
block or two, but if you can alter your route to go slower at first it
might help.

 

[Ratatooie]

This issue has been discussed before.

The solution seems to be better engine warm up.

Let the car idle for 10 minutes or so, whatever is needed
to nicely warm up the engine before taking-off. Apparently
a warmer engine positively affects the transmission (helps
it warm up faster also, I guess).

My understanding is the cooling system has runs that also cool the
transmission.

So, engine heats coolant which heats the transmission when not moving.

If driving, friction will heat up the transmission pretty quickly.

 

[Edward Elhauge]

This issue has been discussed before.

The solution seems to be better engine warm up.

Let the car idle for 10 minutes or so, whatever is needed
to nicely warm up the engine before taking-off. Apparently
a warmer engine positively affects the transmission (helps
it warm up faster also, I guess). Anyway, shifting problems
on take-off may be greatly diminished.

MN

A lot of the replies to my post seem to imply that the AT is
not shifting from 1st to 2nd (because of the cold transmission).
It doesn't feel that way to me, it feels like slipping. When
I start out locked in 1st on a warm day, the car accelerates
very hard up to redline. It isn't going all that fast at redline,
but it feels different than the cold weather problem I've been
seeing.

I could do an experiment to distinguish these two theories.
A) Tonight I'm in warm weather: I'll start on a hill in 1st and floor it.
B) Tomorrow I'm in the snow: I'll start on a hill in 1st and floor it.
If the problem I felt was a lack of shifting, A) and B) should
feel the same. I could also see what my speedometer said at redline.

In terms of transmission fluid level, it could get tricky. At
one point the Subaru dealer overfilled my transmission and it
was overflowing after driving in the mountains, leaving a smoky
smell in the engine compartment. After searching through the
history of the group I found a post where the advice given was
to add a small amount little by little. I could try something
like that.

And I will try the experiment of running the car in idle for
a ten minutes.

On a more theorical level. How would the transmission fluid
filter affect the transmission performance? I could see lower
fluid pressure with a clogged filter and thicker (cold) fluid.
Does the fluid pressure drive any mechanical actions in the AT.
I thought the 4EAT was driven electro-mechanically (not via
hydraulic pressure) and that it never completely locks up the
torque converter. I'd like to learn more about how the stock
setup works, for instance below I'm interested in possible
upgrades.

I'd like some feedback on possible replacements for the torque
converter when I go off warranty. My understanding is that the
stock converter doesn't ever completely lock up and that there
are replacement torque converters that will lock up under
certain conditions. Perhaps I could get slightly better gas
mileage from an upgrade like that. Am I on base with my understanding
of the AT setup and are there any drawbacks to swapping out
the stock torque converter for a 'lock-up' one?

 

[MN]

A lot of the replies to my post seem to imply that the AT is
not shifting from 1st to 2nd (because of the cold transmission).

Well, maybe they just look at the title of your post?

My suggestion was basically to eliminate the possibilty that
this is purely a low temperature related issue. Subaru transmissions
are known to be very sensitive to low temps and exhibit slow shifting
when not adequately warmed up.

If you eliminate this simple possibility then I guess it would
be easier to suspect a mechanical/slipping problem which
you may very well have. Certainly at 90k miles it is a strong
possibility.

MN

 

[Ratatooie]

Couple of tips;

Filling little by little is what I did. I had it flushed and filled at the
dealer (one would assume they know how to fill it) and it worked OK but was
a little off. Then I checked it, and found it was off the bottom of the
stick.

I put some in, drove for OK a few days, found it not so good anymore, and
put more in.

Did that for a while and finally it stopped acting funny after I had put
about .5 to .75 quart in total. All the while, the dip stick to measure
said it was full one time, and not full enough the next time. So it is
pretty easy to not fill it properly when considering there is only a few
quarts in there in the first place.

So the stick is not a good indicator of fluid level... especially if you are
dealing with filling in 20 degree weather. You have to repeatedly measure
it to catch it "low" and fill slowly if it does show up low.

For the theoretical issue, yes fluid viscosity makes a huge difference.

Think about it like this, a small pipe with a balloon at each end filled
with syrup. If you squeeze one balloon the other fills. There are several
balances like this used to switch gears around in an automatic transmission.
The engine "pushing" on the baloon at one end, and the gear setting control
on the other baloon. When the engine stops "pushing" the gear setting drops
to a higher gear as the "acceleration" is not there. If the syrup is cold,
it is harder to squeeze, so the engine is pushing harder (your RPM goes up
as you accellerate) but no shifting occurs because the "pushing" is working
against the resistance of the fluid, not resistance of the road (the other
balloon). So the other side does not switch properly... ending in it not
shifting when you expect it to.

To complicate matters, slipping transmission could also be caused by fluid
level being low as the torque converter is not getting an adequate flow
against it. Likewise for a clogged filter. So, check the fill repeatedly.
Get your filter and fluid changed if you haven't done that in the last 30k
miles. It's cheaper than a new transmission. (Don't forget to re-test a
bunch of times after they fill it as one test of fill is not enough to
determine if it is full.)

So cold transmission with high viscosity (thick) fluid... to the system that
shifts feels like you are REALLY STOMPING on the accelerator because the
difference between one "side" and the other "side" is artificially high. So
it doesn't shift because it thinks you are accellerating. Only, you aren't
as the extra engine energy is being used to push the thicker than normal
fluid.

http://www.howstuffworks.com/search...f=hpaw&page_ref=http://www.howstuffworks.com/

(in particular, page 13 of the auto transmission)

The top links are ads, but the "How transmissions.." and "How torque
converters... " and "how coooling systems..." are very informative in making
the behavior of your Subie from a mystery to something to deal with.

This is not to say you don't have other problems, but chances are its just a
little low and not quite warm enough and that is all.

 

[Bob Lund]

For what it's worth, I had a '83 Saab 900 AT that exhibited exactly the
same symptons. I let the dealer convince me it was a blah, blah, blah
issue. I ended up keeping the car 15 years and the only reason I got rid
of it was that the AT was slipping so often that it was unsafe.

Moral of the story, if it's under warranty, get it fixed. Things only go
downhill from where you are at.

Bob

 

[Sheldon]

I have a 2002 WRX wagon with the 4EAT automatic transmission.

The problem I have is only during cold weather (32 deg F)
after sitting all night. I'll take off from my drive way
in the morning, going uphill, and try to accelerate hard
to match the speed of possible traffic on a rural highway.

The car engine sounds like it's spinning fast, and the tach
shows the RPM rising past 4000. Meanwhile the car is slowly
accelerating to about 10 to 15 mph. Scary, the way people drive
on that road.

Eventually, after driving 10 minutes or so the problem goes
away. This doesn't happen on warm days.

I was thinking that the problem was in the torque converter
linkage. I would think that the gearing itself would make
some sort of grinding sound if the gears were only partially
meshing. What do people think? I have 90000 mi on the WRX
and would love to find something for the dealer to fix
NOW, before the warranty runs out at 100000 mi.

I found the following post on a 4x4 list and wondered if
I could be experiencing something like this:


Slipping when it is cold often means that the line pressure is lower
than it should be and that can be a result of fluid which is too
viscous
or has not been changed recently, plugged filter, dirty valve body
parts, deteriorated rings or seals, and a worn pump.

When I took some transmission classes years ago, the instructor said
always suspect the front pump when this sort of behavior was noticed.
But, as Steve posted, other things can affect it too.

Have you serviced it recently? A service and adjust (if it is one that
has adjustable bands) might be money well spent.

Definitely take the car in and have it checked, if for nothing else than to
get the problem on the record under warranty. If a problem pop up after the
warranty period is over there's a good chance, because you now have the
problem on record, it will get fixed for free.

I know that the transmissions are made to shift differently when cold, and
then go to normal when warmed up, but yours sounds a bit out of the norm.
Some people have resolved the problem by having the tranny flushed and
filled with synthetic fluid. The new gizmos they have today flush the
system completely, so it's not like simply draining out a few drops and then
refilling it like the old days.

Keep us posted. It's very frustrating when you have a great car and are
constantly told a problem is "normal."

My Porsche shifts like stirring a bucket of tar with a stick. "Normal" for
this model and 5 spd tranny. Fun to drive, but...