[Snowy_e91]

Apologies in advance for my lack of understanding, but will do my best to describe the situation.

About two weeks ago I noticed an odd hesitation at low speeds. If was coasting slowly over a speed hump and then pressed the throttle, there would be no response for several seconds, before the engine speed would increase or fluctuate before then responding "normally" again.

This happened a couple of times (car was running both cold and hot when it occurred), but nothing more. It then became worse when it happened when driving through an intersection. After coasting, the car would not respond to throttle at all until then revving as if to catch up, before then driving.

On my way to take it to the local independent mechanic, it drove like an absolute dog. When I put it into Drive, the car hesitated, revs fluctuated without the car moving, generally erratic and confusing. I tried putting the car into manual mode to see if this would confuse the car less so I could at least drive it to the mechanic. This almost immediately threw a "transmission malfunction" message on the iDrive. It went into limp mode, which meant that although I had to crawl to the mechanic, I made it without the worry of being smashed into in the middle of an intersection.

The mechanic's initial feeling after doing some scanning and driving the car was that the valve body sleeves may have failed, thus letting fluid up into the mechatronic; causing erratic electrical behavior as well and mechanical issues due to low fluid pressure.

The car has 133k miles on it, and the ZF transmission was serviced twice (at 65k and 116) before I purchased the car. Though failures of these transmissions at this mileage with servicing would be rare, I know it is not impossible. I called the mechanic who performed the previous transmission service, and he clearly remembered the vehicle. He stated that the valve bodies and mechatronic sleeves appeared to be ok when the service was performed; otherwise he would have replaced them at the time.

The mechanic had another of his technicians run diagnostics without giving him background information, and he generally echoed the initial thoughts.

It seems like the next step is to drop the transmission pan, strain the fluid, and inspect the valve bodies to see if the sleeves have failed and are sucking up fluid.
If this is the case, we replace the sleeves, replace the pan/filter assembly, and replace the fluid. Fingers crossed that this offers a solution.

What strikes me is that as with anything mechanical, failures can occur even when things are maintained. This car was maintained fastidiously by the previous owner, which is one reason I bought the car, but that doesn't mean a transmission can't fail prematurely.

Mechanic is stating that a slim possibility is that once the pan is dropped, the valve bodies appear to be fine, which means nothing can be done short of replacing the transmission - not something insignificant on a car that while is in overall great shape, has 133k miles on the engine.

Has anyone experienced similar problems?

If the valve bodies appear to be "good", is there anything else to hunt for other than things like major mechanical failure of the clutches, torque converter etc.?

As I'm sure you're all aware, it's very frustrating to have issues with a car that are not just a case of diagnosing and replacing with certainty. I appreciate any input that any of you might have!

[GoRomeo]

Well, if the car went into limp mode it means there are codes stored in the DME. Please read codes if you can and stop guessing. This kind of repairs are beyond a “mechanic” who does not especilized iin transmissions. If you can’t read the codes on your own, I would recommend taking your car to a transmission shop fo an accurate diagnosis.

[mainbearing]

Yes the codes please.

[Snowy_e91]

Originally Posted by GoRomeo

Well, if the car went into limp mode it means there are codes stored in the DME. Please read codes if you can and stop guessing. This kind of repairs are beyond a “mechanic” who does not especilized iin transmissions. If you can’t read the codes on your own, I would recommend taking your car to a transmission shop fo an accurate diagnosis.

Codes are as follows:

578E Gearbox oil wear
56BD Clutch gears 2 and 6; Neutral test (this was after putting the car into manual mode. It's known that the wiring for sport mode is crimped, not an uncommon problem)

Recored the next day after another drive:

56BF Clutch, gear 1, 2, 3, 4: Neutral test
56C5 Shift valve B: stuck in off position

[GoRomeo]

Originally Posted by Snowy_e91

Codes are as follows:

578E Gearbox oil wear
56BD Clutch gears 2 and 6; Neutral test (this was after putting the car into manual mode. It's known that the wiring for sport mode is crimped, not an uncommon problem)

Recored the next day after another drive:

56BF Clutch, gear 1, 2, 3, 4: Neutral test
56C5 Shift valve B: stuck in off position

Interesting. Correct I did have the same issue on my e90 where the shifter wiring was crimped out at the bottom. I had to open the center console and slder the broken wires. Luckily there were like 3 brilen wires ans easy to access. This was back in 2012 I believe. But It never gave me any limp mode error’s though. Just maual mode was not responsive to gear changes. You may want to try to tackle this issue first to see if it resolves anything before you take it to any tranny shops?

[gbalthrop]

Originally Posted by Snowy_e91

... If was coasting slowly over a speed hump and then pressed the throttle, there would be no response for several seconds, before the engine speed would increase or fluctuate before then responding "normally" again. [Was there a Delay in Engine RPM increase (throttle LAG), or RPM increase, but NO increase in vehicle Speed (Transmission LAG)?]...
It then became worse when it happened when driving through an intersection. After coasting, the car would not respond to throttle at all until then revving as if to catch up, before then driving. On my way to take it to the local independent mechanic, it drove like an absolute dog. When I put it into Drive, the car hesitated, revs fluctuated without the car moving, [If Engine RPM increased WITHOUT car moving (in Drive), then low Transmission Fluid is FIRST Suspect.] ...
The mechanic's initial feeling after doing some scanning and driving the car was that... [If your mechanic is expressing FEELING instead of Conclusion based upon TESTS, you need to find a qualified SHOP with proper Equipment/ Knowledge. Remember SCIENCE Class? WHAT tests were conducted, with WHAT Diagnostic Equipment, and WHAT were FINDINGS of those tests?] ... The car has 133k miles on it, and the ZF transmission [ZF Transmission on a 2012 E91 328i/xi?] was serviced twice (at 65k and 116) before I purchased the car...
The mechanic had another of his technicians run diagnostics without giving him background information, and he generally echoed the initial thoughts. [We can't read "thoughts" -- got any DATA?? Fault Codes, Live Data, was fluid level checked?]... Fingers crossed that this offers a solution. [NOT a "Scientific approach": Cross Fingers & "Throw Parts" ]...

I realize that YOU probably are NOT into DIY, and have to rely on a $hop to maintain & repair your vehicle. I don't mean to "Be Mean", but DO MEAN to make a point. That point is, when it comes to proper Diagnosis of any vehicle issue: Garbage In = Garbage OUT. If you have relied SOLELY on $hop, please attach Scan of any INVOICE.

As others have stated, Fault Codes, in BOTH DME (Engine Module) & EGS (Transmission Module) are needed as STARTING POINT for DIAGNOSIS. If "Mechanic" didn't provide you with invoice stating the Fault Codes read, and results of tests conducted, he basically STOLE your money. If you have that information on an Invoice, please attach Scan of Invoice. If $hop has records YOU don't, GET COPY from $hop.

Also, if ANY Warning Lights have appeared on Instrument Cluster, please describe specifically, such as SES for engine or Transmission Gear (Yellow or Red) for Tranny. If you have a "!" in yellow triangle to right of Gear indicator in lower Instrument Cluster display, use "Check Control" procedure per your Owner's Manual and Post your "CC-ID" Code(s). Any Fluid Leaks (RED Dexron VI ATF)? BTW, most E91 wagons (unless modified) have GM6 AT which has a METAL Transmission Pan/Sump that holds magnet, vs. ZF plastic sump.

If YOU have a Scan Tool or Diagnostic Software (INPA/ ISTA), please provide those codes, together with Make/Model of Scan Tool or software.
George

[Snowy_e91]

Originally Posted by mainbearing

Yes the codes please.

Codes posted now. Thanks for your reply.

I should note that it appears that the manual mode issue isn't related. Not to say that it is impossible, of course...

[Snowy_e91]

Originally Posted by gbalthrop

I realize that YOU probably are NOT into DIY, and have to rely on a $hop to maintain & repair your vehicle. I don't mean to "Be Mean", but DO MEAN to make a point. That point is, when it comes to proper Diagnosis of any vehicle issue: Garbage In = Garbage OUT. If you have relied SOLELY on $hop, please attach Scan of any INVOICE.

As others have stated, Fault Codes, in BOTH DME (Engine Module) & EGS (Transmission Module) are needed as STARTING POINT for DIAGNOSIS. If "Mechanic" didn't provide you with invoice stating the Fault Codes read, and results of tests conducted, he basically STOLE your money. If you have that information on an Invoice, please attach Scan of Invoice. If $hop has records YOU don't, GET COPY from $hop.

Also, if ANY Warning Lights have appeared on Instrument Cluster, please describe specifically, such as SES for engine or Transmission Gear (Yellow or Red) for Tranny. If you have a "!" in yellow triangle to right of Gear indicator in lower Instrument Cluster display, use "Check Control" procedure per your Owner's Manual and Post your "CC-ID" Code(s). Any Fluid Leaks (RED Dexron VI ATF)? BTW, most E91 wagons (unless modified) have GM6 AT which has a METAL Transmission Pan/Sump that holds magnet, vs. ZF plastic sump.

If YOU have a Scan Tool or Diagnostic Software (INPA/ ISTA), please provide those codes, together with Make/Model of Scan Tool or software.
George

I appreciate how thorough your response is! I do have the quote from the shop, which includes all codes. Note that work hasn't begun on the car, only scanning and test drives have been conducted.

When I drove the car and it ended up in limp mode, the iDrive showed "Transmission Malfunction! Drive Moderately!". The first scan just moments after that happened showed the 578E (Gearbox oil wear) and 56BD Clutch gear 2 and 6; Neutral test.

This is when the shop owner described similar scenarios in this model (this car does indeed have the ZF with plastic pan) being caused by failure of the sleeves around the mechatronic wiring causing fluid to be sucked up into that area, thus lowering fluid level and pressure where it is needed, and causing erratic behavior.

I'm aware that there are hundreds of issues ranging from minor to severe that can cause erratic transmission response, which is why I was initially skeptical of jumping straight into transmission work. I expressed this concern to the shop and it was noted.

The mechanic now plans to drop the transmission pan and strain the fluid to check for debris and inspect the valve bodies. If the sleeves and valve bodies are saturated and look like a point of failure for fluid to seep into, and the fluid is clean, then we could go ahead with replacing the sleeves and the fluid.

Of course if when the pan is dropped, the fluid is full of debris, we have a different scenario entirely....

[Snowy_e91]

Originally Posted by gbalthrop

I realize that YOU probably are NOT into DIY, and have to rely on a $hop to maintain & repair your vehicle. I don't mean to "Be Mean", but DO MEAN to make a point. That point is, when it comes to proper Diagnosis of any vehicle issue: Garbage In = Garbage OUT. If you have relied SOLELY on $hop, please attach Scan of any INVOICE.

As others have stated, Fault Codes, in BOTH DME (Engine Module) & EGS (Transmission Module) are needed as STARTING POINT for DIAGNOSIS. If "Mechanic" didn't provide you with invoice stating the Fault Codes read, and results of tests conducted, he basically STOLE your money. If you have that information on an Invoice, please attach Scan of Invoice. If $hop has records YOU don't, GET COPY from $hop.

Also, if ANY Warning Lights have appeared on Instrument Cluster, please describe specifically, such as SES for engine or Transmission Gear (Yellow or Red) for Tranny. If you have a "!" in yellow triangle to right of Gear indicator in lower Instrument Cluster display, use "Check Control" procedure per your Owner's Manual and Post your "CC-ID" Code(s). Any Fluid Leaks (RED Dexron VI ATF)? BTW, most E91 wagons (unless modified) have GM6 AT which has a METAL Transmission Pan/Sump that holds magnet, vs. ZF plastic sump.

If YOU have a Scan Tool or Diagnostic Software (INPA/ ISTA), please provide those codes, together with Make/Model of Scan Tool or software.
George

I should also add that I agree that finger crossing and throwing parts is superstition at best. I am simply hoping that the solution is not in replacing the transmission!

[gbalthrop]

Originally Posted by Snowy_e91

Codes are as follows:
578E Gearbox oil wear
56BD Clutch gears 2 and 6; Neutral test (this was after putting the car into manual mode. It's known that the wiring for sport mode is crimped, not an uncommon problem)
Recorded the next day after another drive:
56BF Clutch, gear 1, 2, 3, 4: Neutral test
56C5 Shift valve B: stuck in off position

Thanks for posting Fault Codes from EGS. Fault Details show Mileage/km at which any fault was saved. There MAY also be Fault Codes in DME which are relevant to the issue. If YOU have Scan Tool or INPA/ISTA, please provide DME codes. Also, if YOU have INPA, you can read "History Memory" (Historienspeicher) in either DME or EGS, which shows historical record of faults (last 10). That can be helpful in Diagnosis.

If issues are MOSTLY when Low Engine RPM, or when stopped, Transmission Fluid Level is FIRST thing to check, BEFORE ordering any parts. GM6 AT takes Dexron VI Synthetic Fluid. ZF takes Different Fluid, so need to know WHICH tranny you have. Label identifying fluid on bottom of GM6 sump, next to Drain Plug.
George

[Snowy_e91]

Originally Posted by gbalthrop

I realize that YOU probably are NOT into DIY, and have to rely on a $hop to maintain & repair your vehicle. I don't mean to "Be Mean", but DO MEAN to make a point. That point is, when it comes to proper Diagnosis of any vehicle issue: Garbage In = Garbage OUT. If you have relied SOLELY on $hop, please attach Scan of any INVOICE.

As others have stated, Fault Codes, in BOTH DME (Engine Module) & EGS (Transmission Module) are needed as STARTING POINT for DIAGNOSIS. If "Mechanic" didn't provide you with invoice stating the Fault Codes read, and results of tests conducted, he basically STOLE your money. If you have that information on an Invoice, please attach Scan of Invoice. If $hop has records YOU don't, GET COPY from $hop.

Also, if ANY Warning Lights have appeared on Instrument Cluster, please describe specifically, such as SES for engine or Transmission Gear (Yellow or Red) for Tranny. If you have a "!" in yellow triangle to right of Gear indicator in lower Instrument Cluster display, use "Check Control" procedure per your Owner's Manual and Post your "CC-ID" Code(s). Any Fluid Leaks (RED Dexron VI ATF)? BTW, most E91 wagons (unless modified) have GM6 AT which has a METAL Transmission Pan/Sump that holds magnet, vs. ZF plastic sump.

If YOU have a Scan Tool or Diagnostic Software (INPA/ ISTA), please provide those codes, together with Make/Model of Scan Tool or software.
George

Also, no known leaks visible. It was inspected by three different technicians.

[Snowy_e91]

Originally Posted by gbalthrop

Thanks for posting Fault Codes from EGS. Fault Details show Mileage/km at which any fault was saved. There MAY also be Fault Codes in DME which are relevant to the issue. If YOU have Scan Tool or INPA/ISTA, please provide DME codes. Also, if YOU have INPA, you can read "History Memory" (Historienspeicher) in either DME or EGS, which shows historical record of faults (last 10). That can be helpful in Diagnosis.

If issues are MOSTLY when Low Engine RPM, or when stopped, Transmission Fluid Level is FIRST thing to check, BEFORE ordering any parts. GM6 AT takes Dexron VI Synthetic Fluid. ZF takes Different Fluid, so need to know WHICH tranny you have. Label identifying fluid on bottom of GM6 sump, next to Drain Plug.
George

Many thanks, George.

My experience that the problem was only evident from idle/coasting. For example coasting to a red light that turns green (at 15-20 mph), then depressing the throttle would cause the behavior.

What is interesting is that the 578E code has been present intermittently since 117k miles. The most recent transmission service was at 116k miles, and I bought the car at 119k miles. Now at 133k miles. Obviously that code was not enough to show a CEL, nor cause any noticeable symptoms prior to last week.

As an avid car enthusiast who has more skill in driving (and admiring) than doing serious mechanical work, my concern is if fluid is indeed low, how this came to be.

Sure, it could be the issue with the mechatronic sleeve etc., but as a BMW novice, I'm honestly puzzled how it could show the 578E for fluid wear after a transmission service unless that service caused something to occur.

I know relatively little about these cars, so as much as I enjoy driving them, I'm new to this.

[whyzee125]

If the right fluid was used at both services, I doubt your clutches are worn to oblivion. IMO it seems that usually the course of least to most expensive plan of attack is:

1) Pan, mechatronic sleeves & bridge adapter,
2) Plan 1 + solenoids
3) Plan 2 + Sonnax ZIP kit or reman mechatronic

If fluid got into the tcu that may be different. These transmissions, as you know, are generally pretty tough even on high HP 335's so I wouldn't give up hope that she's toast yet!

[gbalthrop]

Originally Posted by Snowy_e91

... I'm honestly puzzled how it could show the 578E for fluid wear after a transmission service unless that service caused something to occur. I know relatively little about these cars, so as much as I enjoy driving them, I'm new to this.

I do NOT claim to be an expert, but my 3/2007 build E91 328xi with GM6 AT first showed Fault Code 578E at 214,544 km = 133,311 miles. INPA "History Memory" still shows that Fault History & Mileage even after "Resetting Counter" with ISTA.

That 578E "Code" cannot be "Cleared" like other fault codes. INPA CANNOT clear it. ISTA can "Reset the Counter". There is NO Transmission Oil Quality Sensor similar to the OZS (Oil Condition Sensor) in the Oil Sump. 578E is set by "Counter", NOT by CONDITION of the Transmission Fluid. So there is NO Relationship between 578E Code & work done on transmission. Even AFTER changing Fluid & Filter, 578E (which does NOT set a warning lamp) remains in Fault Memory UNTIL the "Counter is Reset".

That is based upon my experience using INPA & ISTA, and having TWICE changed GM6 Fluid (drain & refill, NOT flush) & Filter. But don't "Believe Me", use INPA to view your own "EGS History Memory".

BTW, I have ONE instance, at the mileage when I first changed Transmission Fluid, of Fault Code 56BF. That code remains in "History Memory" even after ISTA "Counter Reset" and NO Fault Codes are present in EGS Fault Memory.

So you MAY have something more serious than simple LOW FLUID, but at least Check that First, Delete/Clear ALL EGS Fault Codes, and then see how transmission performs, & if ANY Codes return.
George

[Snowy_e91]

Originally Posted by whyzee125

If the right fluid was used at both services, I doubt your clutches are worn to oblivion. IMO it seems that usually the course of least to most expensive plan of attack is:

1) Pan, mechatronic sleeves & bridge adapter,
2) Plan 1 + solenoids
3) Plan 2 + Sonnax ZIP kit or reman mechatronic

If fluid got into the tcu that may be different. These transmissions, as you know, are generally pretty tough even on high HP 335's so I wouldn't give up hope that she's toast yet!

Thanks for the reply! This seems rational to me, and though anything mechanical can fail prematurely sometimes, I don't want to jump to the most rash conclusion right away.

For some reason, the two local independent mechanics I've spoken with (including the one who has the car currently) are only wiling to go as far as option 1. They both said anything other than pan, sleeves, adapter (and of course new fluid) is a job for the transmission people...

[Snowy_e91]

Originally Posted by gbalthrop

I do NOT claim to be an expert, but my 3/2007 build E91 328xi with GM6 AT first showed Fault Code 578E at 214,544 km = 133,311 miles. INPA "History Memory" still shows that Fault History & Mileage even after "Resetting Counter" with ISTA.

That 578E "Code" cannot be "Cleared" like other fault codes. INPA CANNOT clear it. ISTA can "Reset the Counter". There is NO Transmission Oil Quality Sensor similar to the OZS (Oil Condition Sensor) in the Oil Sump. 578E is set by "Counter", NOT by CONDITION of the Transmission Fluid. So there is NO Relationship between 578E Code & work done on transmission. Even AFTER changing Fluid & Filter, 578E (which does NOT set a warning lamp) remains in Fault Memory UNTIL the "Counter is Reset".

That is based upon my experience using INPA & ISTA, and having TWICE changed GM6 Fluid (drain & refill, NOT flush) & Filter. But don't "Believe Me", use INPA to view your own "EGS History Memory".

BTW, I have ONE instance, at the mileage when I first changed Transmission Fluid, of Fault Code 56BF. That code remains in "History Memory" even after ISTA "Counter Reset" and NO Fault Codes are present in EGS Fault Memory.

So you MAY have something more serious than simple LOW FLUID, but at least Check that First, Delete/Clear ALL EGS Fault Codes, and then see how transmission performs, & if ANY Codes return.
George

Many thanks. It does seem as though these units can behave erratically due to low fluid, especially at low RPM. I'm assuming that this is simply due to low fluid pressure when the level is too low..

[Snowy_e91]

UPDATE:

Some surprises for me, to put it mildly.

Firstly, it is indeed the GM transmission.

Pan was dropped, fluid was clean and clear, neutral safety switch appeared to be badly cracked. That was replaced (along with replacing the fluid and filter) and though the code for failed neutral test disappeared, the car was still driving badly.

Shift valve code was still there, so the advice of the mechanic is to have the valve body replaced. They believe (after consultation with some transmission experts) that the transmission itself is likely okay, and rebuilding the valve body will fix the problem.

This has been quite an adventure.

Now deciding whether at 133k miles if this kind of work is worth doing on a car that I had planned on having for longer trips and so on..

[gbalthrop]

Originally Posted by Snowy_e91

UPDATE:...
Pan was dropped, fluid was clean and clear, neutral safety switch appeared to be badly cracked. That was replaced (along with replacing the fluid and filter) and though the code for failed neutral test disappeared, the car was still driving badly.
Shift valve code was still there, so the advice of the mechanic is to have the valve body replaced. They believe (after consultation with some transmission experts) that the transmission itself is likely okay, and rebuilding the valve body will fix the problem...

Thanks for the details, as MOST do NOT take the time to get them, understand them, or Report Them.

When you report back, please indicate WHAT characteristics were noted: "car was still driving badly".
Thanks,
George

[Snowy_e91]

Originally Posted by gbalthrop

Thanks for the details, as MOST do NOT take the time to get them, understand them, or Report Them.

When you report back, please indicate WHAT characteristics were noted: "car was still driving badly".
Thanks,
George

Similar to before. Although the neutral test fail code had disappeared, the car was hesitating before jerking and then going into limp mode.

The fluid contained no visible debris, so it seems that after the neutral safety switch, the valve body rebuild is all that can be done short of replacing the transmission itself. I should also note that the mechatronic sleeve was intact.

At this point I'm hoping that the relatively low probability (not an impossibility of course) of a transmission failure (mileage and service history etc.) is on my side.

[Snowy_e91]

I should also note that I discussed the issue with a valve body specialist.

He informed me that the "56C5 Shift valve B: stuck in off position" code is a performance code, meaning that it would need to detect a problem doing from 2nd to 3rd gear to throw the code, rather than having an issue in the valve body itself.

I would like to avoid throwing money at parts without knowing 100% (or as close to it as is realistic) what the root cause is. I still have a bad feeling that the valve body (which is $600) won't fix it, and then I'm more than $2,500 in...

[BRG_N54]

Originally Posted by Snowy_e91

What is interesting is that the 578E code has been present intermittently since 117k miles. The most recent transmission service was at 116k miles, and I bought the car at 119k miles. Now at 133k miles.

So it started having error codes 1k miles after the service job? Sounds like the service was less than ideal.

Originally Posted by Snowy_e91

As an avid car enthusiast who has more skill in driving (and admiring) than doing serious mechanical work, my concern is if fluid is indeed low, how this came to be.

My experience is with ZFHP19's, and the fill/drain process is very specific. The fluid has to be in a certain temperature range to get the level correct. If it is allowed to get above 50C it will expand and cause an underfill condition. This scenario describes a bit of what you are seeing.

Originally Posted by Snowy_e91

Sure, it could be the issue with the mechatronic sleeve etc., but as a BMW novice, I'm honestly puzzled how it could show the 578E for fluid wear after a transmission service unless that service caused something to occur.

As mentioned above, the procedures are very specific, including accessing the EGS and resetting the fluid life counter when the service is complete. Again, it sounds like that step may have been missed in your case.

Just to reiterate, my experience is with ZF transmissions, GM may differ. However, I wanted to share what little I know about how they are made and how to service them. Just inside the fluid pan is the valve body, which is bolted to the transmission housing. High pressure hydraulic fluid is passed between these two elements and is contained by several rubber seals. The valve body also contains electrical solenoids, which handle the actual shifting of fluid as the car goes through the gears. This engages different clutches in the transmission housing itself.

The wear items are: 1) fluid 2) clutches 3) solenoids and 4) rubber seals. (There is a filter also, but in the ZF it's built into the pan.) When I did my cars, one was higher mileage and did not shift as well as the other. I did not have any issues like you describe, but it was a similar hesitation while coasting and then applying power. The "full service" would be the items mentioned above, minus the clutches, as they require complete removal and disassembly of the entire transmission.

The valve body was not replaced, but the solenoids were. It eliminated my issue, and now I can't really tell the difference between both cars, in terms of shift quality. Another important aspect that is often overlooked by generic repair shops is to clear the transmission adaptations when you replace parts. There are lots of arguments and urban myths about "adaptations" but my view is if the folks that made the transmission say to do it, then do it.

Anyhow, sorry to be long winded, but this quote:

"56C5 Shift valve B: stuck in off position" code is a performance code, meaning that it would need to detect a problem doing from 2nd to 3rd gear to throw the code, rather than having an issue in the valve body itself.

Sounds like it could be related to the shift solenoids, not the valve body. The seals are cheap and should be replaced anytime you separate the valve body from the transmission housing, IMHO.

[Snowy_e91]

Originally Posted by BRG_N54

So it started having error codes 1k miles after the service job? Sounds like the service was less than ideal.



My experience is with ZFHP19's, and the fill/drain process is very specific. The fluid has to be in a certain temperature range to get the level correct. If it is allowed to get above 50C it will expand and cause an underfill condition. This scenario describes a bit of what you are seeing.



As mentioned above, the procedures are very specific, including accessing the EGS and resetting the fluid life counter when the service is complete. Again, it sounds like that step may have been missed in your case.

Just to reiterate, my experience is with ZF transmissions, GM may differ. However, I wanted to share what little I know about how they are made and how to service them. Just inside the fluid pan is the valve body, which is bolted to the transmission housing. High pressure hydraulic fluid is passed between these two elements and is contained by several rubber seals. The valve body also contains electrical solenoids, which handle the actual shifting of fluid as the car goes through the gears. This engages different clutches in the transmission housing itself.

The wear items are: 1) fluid 2) clutches 3) solenoids and 4) rubber seals. (There is a filter also, but in the ZF it's built into the pan.) When I did my cars, one was higher mileage and did not shift as well as the other. I did not have any issues like you describe, but it was a similar hesitation while coasting and then applying power. The "full service" would be the items mentioned above, minus the clutches, as they require complete removal and disassembly of the entire transmission.

The valve body was not replaced, but the solenoids were. It eliminated my issue, and now I can't really tell the difference between both cars, in terms of shift quality. Another important aspect that is often overlooked by generic repair shops is to clear the transmission adaptations when you replace parts. There are lots of arguments and urban myths about "adaptations" but my view is if the folks that made the transmission say to do it, then do it.

Anyhow, sorry to be long winded, but this quote:



Sounds like it could be related to the shift solenoids, not the valve body. The seals are cheap and should be replaced anytime you separate the valve body from the transmission housing, IMHO.

Thanks for your reply.

My understanding, after doing some digging, is that it's possible with the GM transmission for the check valve which sits between the valve body plates to become worn, causing it to dislodge itself and become stuck between the plates.

My hope is that with a full valve body rebuild, this, along with solenoids would be taken care of.

It also seems as though a software reset and update would be advisable....