2003 H6 Outback slow to downshift

[dburton97128]

My 2003 H6 Outback transmission seems to work very well and shifting is very smooth but I have one complaint.

When attempting to accelerate quickly it is very slow to respond and downshift.  When starting from a full stop it's fine, but if I'm moving forward at much speed it seems to want to stay in high gear.  If I floor it sometimes it's 2-3 seconds before it will downshift.  This has caused me some embarrassment a few time when trying to pull in to traffic and merge and the car just does not go.

There is no floor mat obstruction.

I've seen a few threads where this is complained about but no real solutions mentioned.

Ideally I would have the performance button to resolve this but this car is not equipped with that and it's apparently not feasible to add.

My daughters Impreza 2.5i has very impressive throttle response even with the smaller engine. (electronic throttle)

I've seen mention of removing the battery to get some algorithm to re-learn something.  It that really a thing?

Any suggestions or is this just the way it is?

Thanks.

[idosubaru]

are there any check engine lights?
does the AT light flash 16 times at first start up?

change the transmission fluid. 

engine performance is often mis-interpreted as poor transmission performance.  plugs and air filter would be worth checking or replacing. 

i doubt this is the case but earlier H6's had weak throttle position sensors.  not sure 2003's really have that issue but maybe they do or maybe yours somehow has an 01-02 TPS on it due to prior engine work in the life of the vehicle.

[dburton97128]

No codes.  Tranny fluid has had full flush and replace recently.  New tranny filter.  No extra flashing lights.  Recent plug change as well.

It could be a TPS issue, but I haven't looked more closely at that.  I think this one is still cable actuated.

Would be nice to know how it is supposed to perform if everything is right.

[1 Lucky Texan]

if this is something you only notice when highway passing (above 70mph or so) then yes, try the batt disconnect reset. I ALWAYS do this before a 'road trip' with our 03. It helps with trans 'flare' when passing at high speeds.

the tps is how the trans knows a demand for acceleration has been made.

 

some folks have found use of Trans-X to help with slow engagement - but that is not the same as downshifting really.

Edited June 13, 2019 by 1 Lucky Texan

[dburton97128]

I'm thinking if there is a problem this is most likely the TPS.  Something must signal the tranny to downshift and I assume that is the issue.  Haven't noticed much to complain about at high speed, it's not as big an issue, though it does still take it a bit to decide to downshift.  It's not like the shifting is slow, but more like it is delayed.  Once it decides to shift the shift is smooth and appropriate.

[FerGloyale]

The H6 trans mapping is is setup to maximize the extra torque of the H6.

Subaru compromised the fuel mapping and the shift mapping of the h6 cars to meet fuel economy standards.

I would recommend either manually downshifting, or using a quick "stab" of the throttle to enter "power" mode (old subaru stuff, but still in the mapping, just no light to indicate)  It's not about how far you push the pedal down, it's about how quickly.  Stab it instead of "rolling" into the throttle.

Or like I said, us the shifter to grab 3rd instead of staying in "D" and asking the TCU to do it.

[dburton97128]

The biggest problem with this occurs when I have decelerated to a relatively slow speed (10-30 mph) and then need it to kick into 2nd or even 1st to accelerate into traffic, which is more troublesome to do manually because of the jog.  Also mine won't shift into 1st manually if the car is moving.

[FerGloyale]

1 hour ago, dburton97128 said:

The biggest problem with this occurs when I have decelerated to a relatively slow speed (10-30 mph) and then need it to kick into 2nd or even 1st to accelerate into traffic, which is more troublesome to do manually because of the jog.  Also mine won't shift into 1st manually if the car is moving.

the jog is meant to make it easier to know which gear you are in.  If you can push shifter right, your in 3rd, and can drop to second.  If you can't slide right, then you are either in D or in 2nd. Plus there is an indicator on the dash.

To do the same in my 98 forester you have to press the button to get from 3rd to 2nd, with no indicator on the dash.  I prefer the H6 gated shifter. (my wife has an 03 ll bean)

Anyhow, my point was that what you are experiencing is a characteristic of the model, not a fault in your car.

If you are moving too fast for 1st gear, the downshift won't engage if that's what you mean.  (ie. engaging 1st would over rev the engine, the TCU will not engage 1st, or 2nd or 3rd for that matter if the TCU deems speed to be excessive for the gear.)

How fast are you trying to jump out into traffic if you feel the need to grab 1st gear to get in front of someone? jk.....but really 1st gear is revved out by 15~20 mph.  Second isn't fast enough?  Maybe you need new spark plugs and premium gas (that's what it's supposed to get)  

PS, you are better off trying to jump into traffic in D than 2nd.  When you start off, from a stop or near stop in "2" the TCU will start you in 2 rather than 1st.  If you are in D, it will start you in 1st.  Only use the downshift while moving to pass, or going down hill or into a corner to engine brake.  Use 2 "hold" starting from a stop in very icy situations where you don't want wheel spin.

Edited June 14, 2019 by FerGloyale

[dburton97128]

Good info. Didn't know about the 2nd gear position forcing 2nd instead of 1st. Don't really know if I would need 1st or 2nd when pulling out.  Probably depends on how much I needed to slow down before merging.  All I know is a 2 or 3 second delay to get out of OD or 3rd is the pits for merging in traffic or turning through short gaps in heavy oncoming traffic.

[1 Lucky Texan]

dburton - you DO run high octane fuel as suggested in the manual right?

Edited June 14, 2019 by 1 Lucky Texan

[CNY_Dave]

I use the pedal 'stab' on my forester too! Heck, you can make it downshift coasting downhill with that trick.

The H6 is opposite the 4 cyls in one respect- under cruise control it downshifts *earlier* than with it off. I tested this quite a bit.

So if you disconnect the wire to the TCU and wire it such that the TCU always thinks the cruise is active, it will downshift earlier. Don;t know if that wire does anything else though.

[Numbchux]

There was a TSB about the TPS on H6 models causing mild transmission issues without throwing a code. There is an updated part number from Subaru for it. It's not exactly cheap, so get your hands on the FSM testing page to test the resistance values, but that might be your answer.

That's the only thing I can think of. The Transmission unit uses speed and throttle position to determine the appropriate gear. If it was getting bad speed info, you'd have other symptoms....so it almost has to be TPS.

 

The TCU is a learning unit, so it might be worth doing a capacitive discharge (disconnect the battery for a few minutes, and step on the brake to use up any electricity in the capacitors) to reset things to a factory default. It may be learning some bad habits.

[dburton97128]

Well running premium does up the pep but doesn't change the shifting behavior.  Double pumping the accelerator to pass works fairly nicely though.  Still need to get around to checking the TPS.

[CNY_Dave]

On 6/17/2019 at 1:45 PM, Numbchux said:

There was a TSB about the TPS on H6 models causing mild transmission issues without throwing a code. There is an updated part number from Subaru for it. It's not exactly cheap, so get your hands on the FSM testing page to test the resistance values, but that might be your answer.

That's the only thing I can think of. The Transmission unit uses speed and throttle position to determine the appropriate gear. If it was getting bad speed info, you'd have other symptoms....so it almost has to be TPS.

 

The TCU is a learning unit, so it might be worth doing a capacitive discharge (disconnect the battery for a few minutes, and step on the brake to use up any electricity in the capacitors) to reset things to a factory default. It may be learning some bad habits.

The TCU has separate key-on and always-on power leads, the extreme version of this would be to cut the always-on power lead and connect it to the key-on source.