2003 OB H6 Transmission woes

[Muskiefshr]

Okay…so I’m starting to get at wits end with this car. The car is a 2003 Outback 3.0 H6 non-VDC car with only 68k miles. Being a forest green color car and such low miles and clean, I really want to get the car sorted out. My problem is a Violent 4-3 bang shift. Bad enough that if your going over 45 mph and you 3/4 throttle to floor it to pass/accelerate, it feels and kinda sounds like I got rear ended and will actually chirp the tires. I can’t live with this out here in the mountains in Utah as I’m afraid the trans will kill itself going up a grade one of these days. 
 

Here’s what I have done so far to try to remedy the bang shift. I changed the trans fluid and added trans x to the new fluid…no change in performance. Did the battery disconnect thing to clear the TCU…still no change. Replaced battery and tested alternator(tested good, 13.9v steady)…no change. Replaced the TPS sensor with a brand new Subaru OEM sensor…no change. Then, I found a 2002 OB H6 VDC car that had an interior fire with 160k miles on it. I pulled the trans from it, swapped the center diff on the VDC trans from the VTD one to the MPT one, installed into my 03 with new ATF fluid and a half bottle of trans x, and still no change with the bang shift. On top of that, the ‘new’ trans I installed now slips on the 2-3 up shift. 
 

I’m guessing the used trans I installed is probably not healthy due to the 2-3 slip, but for both transmissions to have the same violent 4-3 bang shift seems unusual to me. I’m wondering what your guys thoughts might be. My girl literally wants me just to part the car out but it’s hard to give up on a clean, low miles Outback. I know it’s uncommon, but could I have a bad TCU? I get no codes or lights with either transmission. Also I’ve been reading about the resistor on the passenger side strut tower…what does that control in the transmission? Could that be an issue?

[idosubaru]

It has the same problem with a new transmission (with original MPT)?

It seems like it has to be:

a. TCU

b. MPT

c. Final drive ratio mismatch (I doubt this is it but I don’t like assuming too much from your diagnosis and my interpretation of types descriptions)

d. Shift resistor (I’ve never seen one fail or cause those symptoms but it completes the list of *things a proper trans needs to shift properly*)

 

lukcily those are all rather simple to diagnose or swap with a cheap used one

1. Youre positive it’s got the right final drive ratio matching trans and rear diff?
2. why does it have so low miles? 
3. I’d swap the TCU. It’s easy and they almost never fail so they’re cheap

4. Scan check engine codes. What do you get?

5. Are there any trans or other lights illuminated on the dash?

 

Unplug the shift resistor - what happens when driving now?  Get a used one and swap it in  

What happens if you manually shift from 1st to 2nd to 3rd to D as needed rather than have it in drive?

If you’re in D and manually shift to 3rd before pressing the gas pedal what’s happens?

[Muskiefshr]

46 minutes ago, idosubaru said:

It has the same problem with a new transmission (with original MPT)?

It seems like it has to be:

a. TCU

b. MPT

c. Final drive ratio mismatch (I doubt this is it but I don’t like assuming too much from your diagnosis and my interpretation of types descriptions)

d. Shift resistor (I’ve never seen one fail or cause those symptoms but it completes the list of *things a proper trans needs to shift properly*)

 

lukcily those are all rather simple to diagnose or swap with a cheap used one

1. Youre positive it’s got the right final drive ratio matching trans and rear diff?
2. why does it have so low miles? 
3. I’d swap the TCU. It’s easy and they almost never fail so they’re cheap

4. Scan check engine codes. What do you get?

5. Are there any trans or other lights illuminated on the dash?

 

Unplug the shift resistor - what happens when driving now?  Get a used one and swap it in  

What happens if you manually shift from 1st to 2nd to 3rd to D as needed rather than have it in drive?

If you’re in D and manually shift to 3rd before pressing the gas pedal what’s happens?

So a few things I can answer right away. 
 

1. I’m 99% positive the final drive matches the rear diff. Both cars are H6 3.0 cars and as I understand, Subaru always ran the 4.11 in all H6 cars. The only difference is my car is a 2003 and the donor car is a 2002. I am not getting any weird torque binding or noises from the rest of the drivetrain as well. 
2. The MPT center diff that I swapped onto the VDC trans looked like it was practically brand new. The clutch pac had virtually no wear and the bearing spun smoothly. I doubt the center diff is my issue but I can’t completely rule it out.

3. not sure why miles are so low. I ran a car fax and it seems legit. Also the rest of the car looks like a low mile Subaru. The car fax showed that the car only did 26k miles up until 2018. The rest of the miles were put on after that with a different owner.

4. I wasn’t able to pull any codes with my scan tool, stored or current. No warning lights illuminated as well. 

5. If I manually shift, it’s not nearly as bad with the bang shift. But it still isn’t great. The 2-3 slip is still there with manual shifting, which leads me to believe that is in the trans. The bang shift is my big concern. 
 

I am going to try swapping the TCM from my parts car, but I don’t think it will work. The parts car is VDC and mine isn’t, which I believe the VDC was a totally different TCM. If I can swap it just to see if it remedies my bang shift, that would be a plus though! I’m still in the dark as to what that resistor does but I’ll mess with that too… it’s certainly easy enough to get to.

[lmdew]

I'd take it to a quality transmission shop and let them do the diagnostics on it.  Many times they can read deeper into the trans.

[1 Lucky Texan]

any dents in the tran's pan?

[Muskiefshr]

1 hour ago, 1 Lucky Texan said:

any dents in the tran's pan?

No dents in the pan. Pan is pretty much like brand new. And filter and filter screen are new as well.

[Muskiefshr]

9 hours ago, lmdew said:

I'd take it to a quality transmission shop and let them do the diagnostics on it.  Many times they can read deeper into the trans.

I’m pretty cheap as far as service goes, so I will do absolutely everything I can before I take it somewhere. Plus most of the shops near me are rip off places that don’t have very reputable reviews.

[idosubaru]

On 12/4/2021 at 12:05 PM, Muskiefshr said:

The only difference is my car is a 2003 and the donor car is a 2002. 

3. not sure why miles are so low. 

4. I wasn’t able to pull any codes with my scan tool, stored or current. No warning lights illuminated as well. 

I am going to try swapping the TCM from my parts car, but I don’t think it will work. The parts car is VDC and mine isn’t, which I believe the VDC was a totally different TCM. If I can swap it just to see if it remedies my bang shift, that would be a plus though! I’m still in the dark as to what that resistor does but I’ll mess with that too… it’s certainly easy enough to get to.

2002 and 2003 is when the rear transfer clutch solenoid wiring was reversed.  I’m a little uncertain on that but that might be a good idea to check  

#4 - they can have “pending” codes, which don’t trigger the CEL.  have to read the codes to see them. good to hear it doesn’t. 

Ive unplugged the shift resistor to firm up lagging slow shifting on 80s and early 90s 4EATs that were known to have slow/lagging shifting from 3-4.  It was minor but enough that some people liked to tinker snd do that. There was nothing wrong with them, they were just like that. We just would disconnect the shift resistor entirely (just unplug it) and the shifts are much more crisp/sharp/fast. Could unplug it and drive but maybe it would have adverse affects on newer subarus. 

FSM may give a simple test you can do.  

[Muskiefshr]

 

So an update. I have messed with the car this week have have no fix yet for the issues. One of the things I did was unplug the resistor under the hood. When I did that, the AT fluid temp light would blink, and it would only shift in first and second gear. I also replaced the resistor with one from a 2004 3.0 car…no change or improvement. I then started swapping TCM’s. I have one from a 2004 3.0 non-VDC sedan, a 2003 2.5 4 cylinder, and a 2002 3.0 VDC car. Tried all of them and there was no improvement on my issues.
The only thing I swapped when I changed transmissions was the center diff and I had to swap the trans wiring harness because the one on my replacement trans got a little scorched in the fire. I’m starting to wonder if there is an issue with that wiring harness or the wiring harness in the car. Going to continue to investigate those avenues. But the car is really starting to frustrate me.
And in case anyone is curious, I did swap the VDC TCM into my non-VDC car and tried it. The non-VDC TCM has 2 plugs versus the 3 on the VDC car. You can plug the two into two of the connections. However when I started the car, I had a CEL, AT fluid temp light, and both the P light and 2 light were illuminated. As soon as I would shift out of park the car would die. It did not like that TCM obviously so I disconnected that one right away!

[Muskiefshr]

On 12/6/2021 at 3:45 AM, idosubaru said:

2002 and 2003 is when the rear transfer clutch solenoid wiring was reversed.  I’m a little uncertain on that but that might be a good idea to check  

I’m fairly sure that Subaru reversed the wiring only for the 2004 transmissions. That’s what most of the subaru guys have been telling me. I know the 2002 and 2003 transmissions I have are wired the same.

[idosubaru]

13 hours ago, Muskiefshr said:

I’m fairly sure that Subaru reversed the wiring only for the 2004 transmissions. That’s what most of the subaru guys have been telling me. I know the 2002 and 2003 transmissions I have are wired the same.

Great, thanks for letting me know those dates.  I didn't think that would be it anyway but good to confirm. 

The resistor and TCM didn't fix it.  Wow. 

What torque converter did you use?  Original or a different one?

I'm not aware of anyway - but I wonder if there's some way for the rear MPT (center diff) could be causing this.  It has to be that or wiring. 

Does the TCM use any engine sensors besides the TPS?