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Transmission Issues (?)
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03-26-2024, 01:47 PM | #1 |
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Transmission Issues (?)
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! |
03-26-2024, 02:58 PM | #2 |
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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.
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03-26-2024, 04:11 PM | #4 | |
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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 |
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03-26-2024, 04:44 PM | #5 | |
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03-26-2024, 05:20 PM | #6 | |
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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 |
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03-26-2024, 05:21 PM | #7 |
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03-26-2024, 05:31 PM | #8 | |
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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.... |
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03-26-2024, 05:33 PM | #9 | |
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03-26-2024, 05:37 PM | #10 | |
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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 |
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03-26-2024, 05:38 PM | #11 | |
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Also, no known leaks visible. It was inspected by three different technicians. |
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03-26-2024, 05:53 PM | #12 | |
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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. |
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03-26-2024, 06:36 PM | #13 |
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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! |
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03-26-2024, 08:04 PM | #14 | |
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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 |
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03-27-2024, 03:32 PM | #15 | |
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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... |
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03-27-2024, 03:34 PM | #16 | |
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04-03-2024, 03:31 PM | #17 |
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Update
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.. |
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04-03-2024, 06:45 PM | #18 | |
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When you report back, please indicate WHAT characteristics were noted: "car was still driving badly". Thanks, George |
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04-04-2024, 03:21 PM | #19 | |
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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. |
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04-04-2024, 03:42 PM | #20 |
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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... |
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04-04-2024, 06:36 PM | #21 | ||||
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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: Quote:
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04-04-2024, 07:40 PM | #22 | |
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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.... |
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