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Problem downshifting automatically on hills/inclines

My 2004 Subaru Legacy Outback has some 70k miles on it, well maintained. i have noticed a problem with the auto shifting recently.

The car starts from stand still to any speed without a problem, but while its in motion, if it encounters any incline or hill, its gives me these little sequence of jerks, i can see the tacho showing some jitter when this happens and it then stabilizes. this happens more often on warm days than cold days.

I got the oil changed, no improvement. anytime i take the car to the mechanic, it wont reveal itself to the mechanics. for them the car is running as smooth as it should. but after some days the problem shows up again.

I am tired of chasing this down and consider this a loss in quality of life :slight_smile: guys help me out.

Your transmission fluid should have been changed at 30k miles and at 60k miles.
Was it?
If not, this is a probable source of your transmission problems–assuming that this is actually a transmission problem.

This could actually be a “driveability” problem involving the engine. Engine performance problems are frequently misinterpreted as transmission problems.
Oil changes are a good thing, but they don’t do anything to help a transmission, and are not a substitute for other types of maintenance.
Were the spark plugs, air filter, and fuel filter changed at 60k miles?

I am assuming that you have already checked the level, color, and odor of the transmission fluid.
If not, you need to do this right away, and then report back to us on your findings as well as on the maintenance history of your car.

raveen.b–Are you still there?

ya the tranny fluid was changed some 5-6k miles earlier,

the air filter was clean at the time of last inspection so it was left as is,

i dont think anyone inspected the spark plugs, may be because its so darn deep inside in the H6 engine that i cant take a look at it with a regular plug wrench. if there was a problem with the plugs the MCU should have put on the check engine light. the check engine was on two times in the past but has gone away mysteriously before i could take it to the mech for reading it out.

the fuel filter was also not changed AFAIK,

tranny fluid level was checked, for color and odor, seemed ok, pinkish with no particular outstanding smells, i also added i qt of of those lucas oil mixtures, only gave mild improvement, the engine oil change is pending, will try to get it done tomorrow.


With all due respect, I have to take issue with your statement that the car has been “well maintained”. The spark plugs were supposed to have been replaced at 60k, and Subaru recommends the replacement of the fuel filter at 30k and 60k. The fact that neither of these maintenance items have been taken care of by 70k makes me suspect more and more that you have created a driveability problem by skipping specified maintenance.

If you wait until those plugs are in bad enough condition to activate a constant CEL, your gas mileage will really deteriorate and what I believe to be a driveability problem will only get worse. At 70k+ miles, even your engine’s power has undoubtedly decreased somewhat as a result of those overage plugs. Since the H6 engine is such a powerful one, you are not likely to notice the slow deterioraton in power output, but–trust me–it has taken place as a result of those plugs.

Also, by leaving the original fuel filter in place for so long, you are placing a lot of added stress on the fuel pump, by causing it to have to work harder to force gas through the partially-clogged fuel filter. Hopefully your driveability problem is not related to a failing fuel pump, but I would suggest that you not press your luck any further with that fuel filter.

Use the same plugs specified in the Owner’s Manual (my '02 H6 engine calls for NGK PLFR6A-11 plugs, but you should verify if yours calls for the same model plug), and remember to be very careful when removing them. Since the plugs have been in place for so long, they could have partially seized in their threads. Whatever you do, make sure that you don’t damage those threads!

There are also other procedures that needed to be done at 60k (coolant replacement and brake fluid replacement, among others), so I am wondering if you skipped those along with the spark plugs and the fuel filter. As to the air filter, this is supposed to be changed at 30k and 60k. Even if it looks OK, I suggest that you change the air filter.

Do yourself a favor and start to follow the mfr’s maintenance schedule.