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Hard downshift knock?? H6 Automatic


2012 Legacy H6
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Hello please give me some advice. I am a new owner of a 2012 Legacy H6.

 

I was just making a left turn and after completely releasing the gas after completing the turn, I heard and felt a significant single KNOCK. Almost as if I hit something but the knock corresponded with the downshift. I was able to recreate this knock once more with another downshift after releasing the gas pedal.

 

There are no codes thrown (yet) and no other signs of a potentially failing transmission.

 

Thank you in advance for any information you can provide.

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  • 1 month later...

What is your mileage?

Has your trans fluid been replaced recently?

 

This symptom is the start of a Valve Body failure.

Keep a close eye on it, it will gradually get worse until it throws a code.

Most cases, that code will be P1710, turbine speed sensor 2.

 

If that is the case, you have one of two options. Valve body replacement(well over a grand for the part alone), or a hall effect sensor(Less than $100 for the part but the labor will be upwards of 3-500 depending on the hourly rate at the shop you decide to go to if you don't do it yourself.

 

I am about to do this sensor replacement and will document the entire process including symptoms, codes, soldering, etc.

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It happened again recently. I was accelerating slowly and the rpms went up weakly then I heard and felt the loud knock and thump. The fluid is good and it started at 96-97K. Has 98K now.

 

 

What is your mileage?

Has your trans fluid been replaced recently?

 

This symptom is the start of a Valve Body failure.

Keep a close eye on it, it will gradually get worse until it throws a code.

Most cases, that code will be P1710, turbine speed sensor 2.

 

If that is the case, you have one of two options. Valve body replacement(well over a grand for the part alone), or a hall effect sensor(Less than $100 for the part but the labor will be upwards of 3-500 depending on the hourly rate at the shop you decide to go to if you don't do it yourself.

 

I am about to do this sensor replacement and will document the entire process including symptoms, codes, soldering, etc.

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  • 4 weeks later...

It finally got worse. Had the trans fail to shift smoothly at 20mph twice in a row. Rpms went up but no power then BAM a hard slam of a shift. No check engine light. A week later I'm driving home and the lights started flashing along with a CEL. Upon acceleration- very weak power. Brought it to Subaru and sure enough its the valve body. Along with that they found external head gasket oil leak as well as one side of the valve cover, displaced control arm bushings, manifold leaks as well. All together the estimate is over 6K.

 

What is your mileage?

Has your trans fluid been replaced recently?

 

This symptom is the start of a Valve Body failure.

Keep a close eye on it, it will gradually get worse until it throws a code.

Most cases, that code will be P1710, turbine speed sensor 2.

 

If that is the case, you have one of two options. Valve body replacement(well over a grand for the part alone), or a hall effect sensor(Less than $100 for the part but the labor will be upwards of 3-500 depending on the hourly rate at the shop you decide to go to if you don't do it yourself.

 

I am about to do this sensor replacement and will document the entire process including symptoms, codes, soldering, etc.

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Typically when an H6 goes wrong a low-mileage JDM engine is swapped in.

 

I did the rebuild route for head gaskets and wished I'd just swapped it. I think I was around $7k and five months in free loaner cars. A JDM swap would have been about $3k.

 

That was right after I bought it.

 

Two years later, I'm still the happy owner of this beautiful car, and the engine still runs like brand new. Almost to 200k miles now! It was worth it, but I'm not sure if I would do it again.

Edited by Rcnesneg
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  • 2 weeks later...

So they repaired everything except for the left side head gasket seep... so your recommendation would be to swap it with a JDM engine? 3K is for the engine alone? Or labor included?

 

Typically when an H6 goes wrong a low-mileage JDM engine is swapped in.

 

I did the rebuild route for head gaskets and wished I'd just swapped it. I think I was around $7k and five months in free loaner cars. A JDM swap would have been about $3k.

 

That was right after I bought it.

 

Two years later, I'm still the happy owner of this beautiful car, and the engine still runs like brand new. Almost to 200k miles now! It was worth it, but I'm not sure if I would do it again.

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