Calling ZF 8HP Experts

[Craig in Canada]

Hi all:

I’m looking to DIY tackle some things that have been bothering me about my 8HP for many years and I’m hoping that there are some folks here with some experience who could offer some advice. This is a 2011 BMW 535i X-Drive with 8HP45Z in AWD configuration and around 143,000km / 88,000mi on the odo. I have DIYed a pan and fluid change a couple of years ago, the dealer may have at my request as well. I do everything by the book using ZF instructions and have access to ISTA+ to pull codes.

I am planning to do another pan change, and drain/fill with ZF LG8. I have 90%+ decided that I will be changing the solenoids. I’m wondering if there is anything else I should be looking at doing at the same time (e.g. any of the kits from Sonnax). I don’t want to do any unnecessary, risky work in the valve body that I do not need to do. However, at the same time I would like to fix my problems if I can. As an enthusiast, these are really detracting from my enjoyment of the car, even though lots of “appliance drivers” might not even notice the issues.

This will already be too long so I won’t post details here, but I’ve looked at some shift logic diagrams, and wondered if I should get any additional valvebody parts/kits for Clutch C or E (because C and E are involved in 1-2, 2-3 and 2-1 - all of which I have issues with, and C has high adaptation)

Some of the problems I’ve been having have been there since the car was in factory warranty and had <30,000km, but there were never any codes and I could never demonstrate problems serious enough to warrant any action while under factory or extended-factory warranty. Of course many problems chose not to show themselves when the dealer foreman was in the vehicle.

There has never been a single transmission code set that can be seen with ISTA. As long as I can remember clutch C has had a borderline high adaptation pressure >300mbar.

Today’s adaptations (I can provide more historical values if needed):

• Clutch A: -102 mbar 18ms
• Clutch B: -84 mbar 48ms
• Clutch C: 350 mbar 21ms
• Clutch D: 96 mbar 13ms
• Clutch E: 242 mbar 15ms

Description of my problems:

• One of the oldest problems - a noise during the 1-2 and sometimes 2-3 upshift. If it’s making the noise (never would with a dealer foreman in the car) it usually happens during light-medium acceleration (very light acceleration won’t do it, and driving more aggressively makes it go away too). The shifts feel slow when it’s happening. I would call it “extra protective” of the transmission - seems to be a lot of power cut and it takes a long time to do the shift. The noise is most audible with everything closed up and it sound like someone a few lanes over spinning their tires in the rain. The noise ramps up just before the shift itself starts and ramps down after it’s complete. I think the noise is from the transmission as it is synchronized with the shift, but that is unconfirmed with something like chassis ears.
  
  
• Also a very old problem: Lurch in take off from brief stops. I believe this is actually a VERY slow 2->1 downshift when stopping. This is worst in situations like neighbourhood 4 way stop intersections with no traffic, where I come to a stop and immediately proceed. At first the power seems to go nowhere, and then the car lurches forward and starts accelerating with no change in engine character when the lurch happens. Disabling neutral idle control seems to help a little with this, but it doesn’t fix it. I believe I'm taking off in 2, even though the dash shows 1 the shift hasn't completed. When I stop longer this doesn't happen. Even light acceleration demonstrates the issue.
  
  
• When neutral idle control is enabled, creeping forward feels pulsed and surge-y.
  
  
• When cold (e.g. below -8C or -10C) the 2-3 upshift (or was it 3-4) will hunt back and forth the first few times. This is a very new problem. In these temps I’m driving very gently when the vehicle isn’t warmed up and I’ve experienced this a couple of times. If it was the only thing, I'd chalk it up to being cold.
  
  
• The transmission is making some bad shift decisions of late, or failing to complete a shift when it calls for it, then the shift comes late with a jerk. Not all the time, but more than it should.

So:

• Is there support for changing solenoids as a solid idea?
• Anything else I should look at, or merely see what happens after solenoids and fluid?
• Any more info or clarification I can provide?

Thanks!

 

[Cujet]

Are you thinking the solenoids are sluggish? Have you tested the resistance (ohms) or removed them to check for free operation?

Do any of these problems exist when shifting manually? My Jag takes off in 2nd all the time. It's annoying and unnecessary. I'd much rather it use 1st properly.

While I don't know enough of your situation to even make a guess, I've found that working with a custom tuner will often fix a bunch of issues that seem to be mechanical, but are in fact, just crummy or 'eco' tuning. The transmission tune on the Jag F-Type (similar trans) is an absolute must.

It seems the 45 series may have interchangeable solenoids they are color coded I think. If possible in your situation, if you want to save money, why not swap a few from good locations for troubleshooting? I am reading it is common practice to replace the solenoids. Some people report good results.

 

[BMWTurboDzl]

Hi all:

I’m looking to DIY tackle some things that have been bothering me about my 8HP for many years and I’m hoping that there are some folks here with some experience who could offer some advice. This is a 2011 BMW 535i X-Drive with 8HP45Z in AWD configuration and around 143,000km / 88,000mi on the odo. I have DIYed a pan and fluid change a couple of years ago, the dealer may have at my request as well. I do everything by the book using ZF instructions and have access to ISTA+ to pull codes.

I am planning to do another pan change, and drain/fill with ZF LG8. I have 90%+ decided that I will be changing the solenoids. I’m wondering if there is anything else I should be looking at doing at the same time (e.g. any of the kits from Sonnax). I don’t want to do any unnecessary, risky work in the valve body that I do not need to do. However, at the same time I would like to fix my problems if I can. As an enthusiast, these are really detracting from my enjoyment of the car, even though lots of “appliance drivers” might not even notice the issues.

This will already be too long so I won’t post details here, but I’ve looked at some shift logic diagrams, and wondered if I should get any additional valvebody parts/kits for Clutch C or E (because C and E are involved in 1-2, 2-3 and 2-1 - all of which I have issues with, and C has high adaptation)

Some of the problems I’ve been having have been there since the car was in factory warranty and had <30,000km, but there were never any codes and I could never demonstrate problems serious enough to warrant any action while under factory or extended-factory warranty. Of course many problems chose not to show themselves when the dealer foreman was in the vehicle.

There has never been a single transmission code set that can be seen with ISTA. As long as I can remember clutch C has had a borderline high adaptation pressure >300mbar.

Today’s adaptations (I can provide more historical values if needed):

• Clutch A: -102 mbar 18ms
• Clutch B: -84 mbar 48ms
• Clutch C: 350 mbar 21ms
• Clutch D: 96 mbar 13ms
• Clutch E: 242 mbar 15ms

Description of my problems:

• One of the oldest problems - a noise during the 1-2 and sometimes 2-3 upshift. If it’s making the noise (never would with a dealer foreman in the car) it usually happens during light-medium acceleration (very light acceleration won’t do it, and driving more aggressively makes it go away too). The shifts feel slow when it’s happening. I would call it “extra protective” of the transmission - seems to be a lot of power cut and it takes a long time to do the shift. The noise is most audible with everything closed up and it sound like someone a few lanes over spinning their tires in the rain. The noise ramps up just before the shift itself starts and ramps down after it’s complete. I think the noise is from the transmission as it is synchronized with the shift, but that is unconfirmed with something like chassis ears.
  
  
• Also a very old problem: Lurch in take off from brief stops. I believe this is actually a VERY slow 2->1 downshift when stopping. This is worst in situations like neighbourhood 4 way stop intersections with no traffic, where I come to a stop and immediately proceed. At first the power seems to go nowhere, and then the car lurches forward and starts accelerating with no change in engine character when the lurch happens. Disabling neutral idle control seems to help a little with this, but it doesn’t fix it. I believe I'm taking off in 2, even though the dash shows 1 the shift hasn't completed. When I stop longer this doesn't happen. Even light acceleration demonstrates the issue.
  
  
• When neutral idle control is enabled, creeping forward feels pulsed and surge-y.
  
  
• When cold (e.g. below -8C or -10C) the 2-3 upshift (or was it 3-4) will hunt back and forth the first few times. This is a very new problem. In these temps I’m driving very gently when the vehicle isn’t warmed up and I’ve experienced this a couple of times. If it was the only thing, I'd chalk it up to being cold.
  
  
• The transmission is making some bad shift decisions of late, or failing to complete a shift when it calls for it, then the shift comes late with a jerk. Not all the time, but more than it should.

So:

• Is there support for changing solenoids as a solid idea?
• Anything else I should look at, or merely see what happens after solenoids and fluid?
• Any more info or clarification I can provide?

Thanks!

88k miles seems absurdly early for solenoids, especially since the ATF has already been serviced twice. I wonder if the AWD system is causing the behavior you're talking about however the 1-2 upshift has always been a little lurchy. IMO the 2-1 downshift should almost never happen unless you come to a complete stop being that 1 is extremely short.

As for the Sonnax kits I would reach out to German Motor Works in Wichita KS. The owner used to release YT content and in one of his episodes he serviced the mechatronics of a ZF6HP with the Zip Kit and Iirc it wasn't his first time.

There's also https/:www.thetctsc.com

The owner, who no longer may be alive, was a ZF engineer.

 

[Craig in Canada]

Are you thinking the solenoids are sluggish? Have you tested the resistance (ohms) or removed them to check for free operation?

Sluggish, or perhaps there are seal issues? Adaptations are high, though on the pressure side, not so much the timing side. (Does anyone know what that might signify?) I've read reports from people with problems similar to some of mine, though generally at much higher mileage, which were all fixed up by solenoids. Despite being expensive, it might be the least expensive possible true fix for some of these.

This is my only car. Cracking open the transmission is a job that requires planning and time set aside (and all the parts I think I might need in advance). I haven't been in there for valve body exploration yet, just the fluid change so far.

I guess something of particular note is that something has been wrong almost right from the start, but not wrong enough to get a warranty case approved. Other F series bimmers with the same transmission don't drive this way. I've also noticed downshifts in D being slower to respond than they were before, driving more like old 90s automatics than 8HPs.

Do any of these problems exist when shifting manually? My Jag takes off in 2nd all the time. It's annoying and unnecessary. I'd much rather it use 1st properly.

Yes, they can. I use all shift modes and enjoy driving manual just to hold gears a little longer. I really miss driving stick, and enjoy the sound of my exhaust in the summer. I do not beat on my equipment, but I use manual quite a lot in nice weather just so I can hear something above 2500 rpm

I have thought about setting it to always take off in 2nd to avoid the lurch, and may do that as a troubleshooting step.

While I don't know enough of your situation to even make a guess, I've found that working with a custom tuner will often fix a bunch of issues that seem to be mechanical, but are in fact, just crummy or 'eco' tuning. The transmission tune on the Jag F-Type (similar trans) is an absolute must.

I have flashed xHP and made a few of my own tweaks to the settings over the years. When I first installed it in 2017/2018 I was hoping that it would improve or cover up a lot of the less-pleasing shift issues, especially since my example did not have the "sport" transmission option (same hardware, same software, different maps).

xHP is the favourite thing I've done to the car, but hasn't fixed the issues. The annoyances are there regardless of whether I'm using stock maps or not. The flash hasn't made anything worse.

It seems the 45 series may have interchangeable solenoids they are color coded I think. If possible in your situation, if you want to save money, why not swap a few from good locations for troubleshooting? I am reading it is common practice to replace the solenoids. Some people report good results.

Perhaps... I'm not entirely sure whether that saves money, considering all the extra pan drops, specific fluid leveling procedures and if I put any value on my time compared to getting all new and being done with it. It's not like swapping coils around to troubleshoot a misfire. The biggest thing is whether collective wisdom feels that solenoids are definitely not an issue and it would be a complete waste of time and money.

I'm reasonably confident I don't have issues with the gears, clutches and bearings, but I am not sure if I have other valve body issues that solenoids won't fix.

88k miles seems absurdly early for solenoids, especially since the ATF has already been serviced twice. I wonder if the AWD system is causing the behavior you're talking about however the 1-2 upshift has always been a little lurchy. IMO the 2-1 downshift should almost never happen unless you come to a complete stop being that 1 is extremely short.

I agree - but something has been off from the start. What if there's a tear in a seal, defective solenoid, or partial blockage or something? That's what I was thinking. For general wear and tear - it's early without a doubt. I was wondering if my 1-2 noise could be too much overlap when one solenoid is supposed to open while another one closes, and they end up both open or both closed due to sluggishness or leaks. Not bad enough to throw a code, but enough for me to notice something isn't right.

For my 2-1 problems I am referring to short but complete stops. Back when under warranty, loaner cars with the same transmission didn't do what mine has done right from the beginning (to my recollection anyways). With xHP installed, the cluster will show me the current target gear in all modes, even D. I see it change to D1, but I think the shift takes a full second or two, and happens when I've already applied throttle to leave the stop sign.

xHP used to let me change the display to show current actual gear, not target gear, but I haven't seen that option recently so they may have removed it. I'll go dig into that.

As for the Sonnax kits I would reach out to German Motor Works in Wichita KS. The owner used to release YT content and in one of his episodes he serviced the mechatronics of a ZF6HP with the Zip Kit and Iirc it wasn't his first time.

There's also https/:www.thetctsc.com

The owner, who no longer may be alive, was a ZF engineer.

I see the kits and lots of available info at the CTSC and I've done a bunch of research there. I guess the trick is knowing whether any of that stuff would help or not.

The instructions from Sonnax for their ZIP kit has lots of great info such as:

• Clutch Valve E can be responsible for slip on 1-2, gear ratio codes, E clutch burned
• Priming Valve can be responsible for delayed engagement, wrong gear starts, and flare/harsh/neutral shifts (and more)
• B2 Clutch NIC Valve can be responsible for NIC concerns, among other things like flare/hard shifts

Multiple components could be responsible for the things I'm experiencing, I guess.

I may also look around for a reputable shop that does nothing but ZF internal repairs (if I can find one in reasonably distance). The vacuum tests called for by Sonnax may be the only way to tell what's going on for sure, and that's probably above my confidence level to DIY. Maybe if it was a project car.

 

[Vaca]

Just my experience with an e60 530i - it has the ZF 6HP trans, not the 8HP like in your BMW, so may or may not be directly applicable. I kept the car until it had 240,000 miles and the only thing I did with the transmission was to change the fluid twice, around 90,000 and 160,000 miles. I used the ZF LifeGuard 6 fluid. I'd be surprised if the solenoids in your car are bad especially considering you've changed the fluid already and it does not have many miles. And it's probably unlikely the mechatronic seals are leaking. Maybe there is a way for you to reset the transmission adaptations using the ISTA software? I would try that before dropping the valve body and replacing the solenoids. Also, I'd imagine that you've checked the fluid level, but I would certainly double check that before dropping the pan to work on the valve body.

 

[TexasRally]

What I-Level (software version) is the car at?

Have to remember the transmission is always doing a tango with the DME, DSC, xDrive, and other modules. Any number of other modules could be influencing some or all of these behaviors (though probably not the noise). xHP alone would change the TCU map but not necessarily how the TCU reacts to inputs from other modules such as torque cut or shift speed requests during normal driving.

Given it’s an early 8HP and F-Series model there could easily be a software explanation here.

My F15 X5 at 186k miles has no issue, but I do get the “brief stop lurch” only when cold at a specific slightly uphill stop sign leaving my neighborhood. It does cut a lot of torque during mid throttle shifts in comfort mode but it’s never bothered me. Switch to sport mode if I want sportier shifting.

I updated the car several years ago and there were updates to basically everything, including the transmission module. The transmission behavior felt more polished afterwards jumping to 6 year newer software, but I’d only owned it a couple months before updating. There were half a dozen other changes too, so don’t discount how much they tweak unannounced.

 

[Craig in Canada]

What I-Level (software version) is the car at?

Have to remember the transmission is always doing a tango with the DME, DSC, xDrive, and other modules. Any number of other modules could be influencing some or all of these behaviors (though probably not the noise). xHP alone would change the TCU map but not necessarily how the TCU reacts to inputs from other modules such as torque cut or shift speed requests during normal driving.

An excellent point - I had a random shower thought that I should have included this in my post .

The vehicle was upgraded to istep F010-17-11-520 by the dealer during the tail end of extended factory warranty. xHP was first flashed in April 2019.

I ran into a few odd things with the vehicle because it's an early-ish F10 with the 205 transmission option (not 2TB) and it did not come with a DEC switch (comfort/normal/sport) of any kind. Originally the xHP authors assumed all F10 vehicles had a DEC switch so their maps didn't account for this.

They sorted it out, but since then I have retrofitted the proper DEC switch and updated coding.

I know that for some this seems like a lot of stuff to have changed, but the annoying behaviours were present since 2014 when everything was bone stock for years. Overall xHP has made the car far more enjoyable. The annoying things slowly get more annoying, but the retrofits and flash has only helped, never made it worse.

I have been reluctant to reset adaptations because of information like this, warning that it may cause harm or failure if you have high adaptations already, and my clutch C and E always have. Ironically the same article says 400 is considered "out of tolerance" but the transmission "works fine" up to 700. Maybe I'll try it before spending $$ on parts.


I'm thinking about placing an order for some parts - still on the fence about solenoids. I already have the mechatronic connector to install to prevent leaks. Does the 8HP have any other seals or sleeves between the valve body and the rest of the transmission I should replace? The filter/pan kit doesn't come with anything, and all the online info on the 6HPs shows various things you should replace since there may be leaks between the valve body and the rest of the transmission. I don't see anything concrete like this for the 8HP and that would also explain issues I'm having.

As mentioned before - I'm frustrated because there's clearly been issues since it was built, but below the threshold for codes and therefore warranty. The TCU thinks everything is working perfectly, it seems.

 

[Craig in Canada]

Also, I'd imagine that you've checked the fluid level, but I would certainly double check that before dropping the pan to work on the valve body.

Yep - each refill it's bang on. New fluid has improved character overall (I can tell the difference after) but the documented annoyances remain intact.

As documented in my post a couple of minutes ago, I have never reset adaptations (dealer may have) because I've never changed any hardware.

I have briefly read up on the long relearning procedure for ZF - I doubt I could ever find a piece of road to do what's required. (of course, neither could the local dealer, so...)

I've seen "quicklearn" mentioned for non-BMW brands. I don't believe I've ever seen that function in ISTA or other tools. Another thing for my list...

 

[TexasRally]

Yep - each refill it's bang on. New fluid has improved character overall (I can tell the difference after) but the documented annoyances remain intact.

As documented in my post a couple of minutes ago, I have never reset adaptations (dealer may have) because I've never changed any hardware.

I have briefly read up on the long relearning procedure for ZF - I doubt I could ever find a piece of road to do what's required. (of course, neither could the local dealer, so...)

I've seen "quicklearn" mentioned for non-BMW brands. I don't believe I've ever seen that function in ISTA or other tools. Another thing for my list...

When you retrofitted the DEC was the VO changed? Was the entire car recoded?

Given how tedious swapping solenoids would be, I’d consider doing a full vehicle software update before potentially wasting any money on physical parts. Risk of the new solenoids exhibiting the same behavior if it’s a transmission control issue.

Latest doc I have from March indicates the latest available software for the F10 is November 2024. That’s a whole 7 years for them to have potentially adjusting the behavior you’re seeing.

Resetting adaptations would probably be my next step after software update. It’s free to do, and if it goes poorly then you could swap solenoids as step 3/last resort.

 

[Craig in Canada]

When you retrofitted the DEC was the VO changed? Was the entire car recoded?

I updated the VO and then ICM KOMBI EGS and GWS were coded. My vehicle has no adaptive components - never had EDC, hydraulic steering because X-Drive. All the DEC does is change parameters in xHP and MHD, which was worth the cost of the used switch and install effort.

Given how tedious swapping solenoids would be, I’d consider doing a full vehicle software update before potentially wasting any money on physical parts. Risk of the new solenoids exhibiting the same behavior if it’s a transmission control issue.

Latest doc I have from March indicates the latest available software for the F10 is November 2024. That’s a whole 7 years for them to have potentially adjusting the behavior you’re seeing.

Hmmm. While I wish it was, that's not something I'm equipped to do myself (in terms of both equipment and courage). I also have no backup plan if anything in the process doesn't go exactly as expected. I'd expect the local dealer to be >$1000 for a "just because I asked" head to toe reflash, plus whatever doesn't go according to plan. I will poke around in my area and see. The case to do this would be stronger in my head if I was still running an istep from 2011. I'm not sure how much attention BMW would be paying to 2011 cars in updates between 2017 and 2024, but it's possible.

Resetting adaptations would probably be my next step after software update. It’s free to do, and if it goes poorly then you could swap solenoids as step 3/last resort.

I've been looking at possibly doing that, though read more issues online where resets made things worse. ISTA has two different resets in transmission service functions with very slightly different wording. Perhaps the original German was more clear which were driver adaptations and which were hardware adapation. I'm assuming the "read and reset" function that shows the clutch fill pressures and time is the correct one we're talking about.

While researching all the various things I see a lot of posters confusing 8HP and 6HP issues. It seems to me that there are no extra seals I can change between the mechatronic/valvebody and the rest of the transmission on the 8HP, just the mechatronic plug seal. The 6HP has the sleeves which can be changed. Do you have any advice there? A pressure leak or two could cause everything I've been seeing. Regardless of anything else I do, another fluid/filter swap is planned for early summer. I'd like to change anything I can while in there (and that's where I'll potentially change the solenoids).

 

[The Critic]

plus whatever doesn't go according to plan. I will poke around in my area and see. The case to do this would be stronger in my head if I was still running an istep from 2011. I'm not sure how much attention BMW would be paying to 2011 cars in updates between 2017 and 2024, but it's possible.

BMW's do have a tendency to fry things when you flash them, so beware.

 

[Craig in Canada]

BMW's do have a tendency to fry things when you flash them, so beware.

Oh yah, definitely. Not counting on a smooth and adventure-free day if I were to try such a thing. I would like to develop my skills and equipment here, but there's a lot of expensive downside in my particular situation.

General update:
I have some parts on order and have been considering potentially getting a remanufactured valve body with solenoids that has been extensively tested and repaired off-vehicle. Then anything and everything relating to the valvebody/mechatronics will be fixed and/or ruled out. Also located a full set of mechatronic seals I could only find at CTSC which is enroute to me.

 

[Marcozi]

Oh yah, definitely. Not counting on a smooth and adventure-free day if I were to try such a thing. I would like to develop my skills and equipment here, but there's a lot of expensive downside in my particular situation.

General update:
I have some parts on order and have been considering potentially getting a remanufactured valve body with solenoids that has been extensively tested and repaired off-vehicle. Then anything and everything relating to the valvebody/mechatronics will be fixed and/or ruled out. Also located a full set of mechatronic seals I could only find at CTSC which is enroute to me.

Contact Clinebarger. He seems to be the transmission guru here.