[WesamJaber]

Hey everyone, I’m a bit stuck deciding whether I should service my transmission or replace it entirely on my 2011 F10 535i.

Whenever I go WOT in 3rd gear, once the car reaches around 5,000–5,500 RPM, the transmission immediately shifts into 8th gear and goes into limp mode. I’d need to restart my car to get it back to normal. Outside of that scenario, I don’t experience any slipping, and the transmission shifts smoothly, especially during normal cruising and day-to-day driving.

For context, the car is running an upgraded turbo custom tuned with many supporting mods pushing around 425-450 wheel hp, and it’s currently at ~140k miles. I could pick up a low-mileage used transmission for around $500–$700, but it’s a tough call when the car otherwise drives perfectly fine under normal conditions.

Has anyone experienced something similar or recognize what these codes might point to? Any recommendations on whether this is something that could be fixed with servicing, or if replacement would be the smarter move? Appreciate any insight, thanks.

Transmission: ZF8HP45

[markivvv]

According to XHP, typical values are between -400 and 400 mbar for the quickcharge pressures and -40 and 40 ms for the quickcharge time. You have a couple small outliers but the clutch A quickcharge time is almost 4x the typical value. There's a good chance that your trans is on its way out.

The 8hp is generally reliable but if you're going above the torque rating and removing torque limits with XHP shit starts to get questionable. ZF officially rates the 8hp45 for 450nm torque (330ftlbs). It can obviously handle a bunch more torque but that comes at the cost of longevity. If you're running 450whp you're WELL past the torque figure it was originally designed for / rated to hold.

When was it last serviced and how long have you been running this setup? I doubt a trans service will be enough to save it but it can't hurt

[WesamJaber]

Originally Posted by markivvv

According to XHP, typical values are between -400 and 400 mbar for the quickcharge pressures and -40 and 40 ms for the quickcharge time. You have a couple small outliers but the clutch A quickcharge time is almost 4x the typical value. There's a good chance that your trans is on its way out.

The 8hp is generally reliable but if you're going above the torque rating and removing torque limits with XHP shit starts to get questionable. ZF officially rates the 8hp45 for 450nm torque (330ftlbs). It can obviously handle a bunch more torque but that comes at the cost of longevity. If you're running 450whp you're WELL past the torque figure it was originally designed for / rated to hold.

When was it last serviced and how long have you been running this setup? I doubt a trans service will be enough to save it but it can't hurt

I’ve ran this setup for quite sometime now. I was stage 2+ with stage 3 xhp for a few years now but recently started custom tuning with my upgraded turbo now. Everything was fine until I did my final revision. I never personally did a fluid change and don’t know if the old owner did either (I doubt it). My plan is to do the fluid and filter change. I might switch to rod sutphins recommended race trans fluid. I know my quick charge pressure sucks but I don’t have any slip at all even at WOT. So I think the fluid might be worth it. I’ll update once it’s done sometime next week.

[ctcarbonari]

140k miles and no idea of the history of your tranny fluid?

When changing the pan/filter I'd consider replacing the mechtronic sleeve and possibly the solenoid seals (while you're there).
The California Transmission Supply Company (thectsc.com) puts together nice ZF rebuild kits but I just noticed their website is blocked?

Send a sample of your old fluid out for OA and consider doing a second "dump & fill" shortly after the initial service (to get 80%+ new oil into the system)

Then cross your fingers and go from there.

[WesamJaber]

Originally Posted by ctcarbonari

140k miles and no idea of the history of your tranny fluid?

When changing the pan/filter I'd consider replacing the mechtronic sleeve and possibly the solenoid seals (while you're there).
The California Transmission Supply Company (thectsc.com) puts together nice ZF rebuild kits but I just noticed their website is blocked?

Send a sample of your old fluid out for OA and consider doing a second "dump & fill" shortly after the initial service (to get 80%+ new oil into the system)

Then cross your fingers and go from there.

I’m ordering the service kit now. I’m contemplating since I am custom tuned if I should get the adrenaline speed shift transmission fluid. I’d rather get oem zf lifeguard fluid personally but have you heard good things of the other one I mentioned?

[ctcarbonari]

Personally, I'd stick with ZF LifeGuard8 (or 9) for the 8HP transmission.
I don't see the benefit in gambling with aftermarket oils on my transmission.

Fluid, in and of itself, is not going to "fix" a mechanical issue. No matter who makes it.

[WesamJaber]

Originally Posted by ctcarbonari

Personally, I'd stick with ZF LifeGuard8 (or 9) for the 8HP transmission.
I don't see the benefit in gambling with aftermarket oils on my transmission.

Fluid, in and of itself, is not going to "fix" a mechanical issue. No matter who makes it.

I forgot to mention that my tuner and I were able to resolve the issue in my most recent revision. The problem where the transmission would get stuck in 8th gear after going WOT in 3rd was fixed by lowering the reported torque. It seems like the transmission was freaking out when torque spiked too high, which makes sense given that 3rd and 6th gear clutches are already known weak points.

This only ever happened right around 5500 RPM, where I consistently saw torque limiters in the MHD logs. Overall, there’s no question the transmission has normal wear and tear at this point, even though it’s not slipping yet, which is why I’m still considering servicing it.

As for the fault codes I had, they could be related to a leaking mechatronic sleeve, which we’re replacing as well. Given everything, im leaning towards sticking with oem fluid, I’ll give an update when I service it hopefully this week. 140k miles wish me luck lol.

[ctcarbonari]

Originally Posted by WesamJaber

I forgot to mention that my tuner and I were able to resolve the issue in my most recent revision. The problem where the transmission would get stuck in 8th gear after going WOT in 3rd was fixed by lowering the reported torque. It seems like the transmission was freaking out when torque spiked too high, which makes sense given that 3rd and 6th gear clutches are already known weak points.

This only ever happened right around 5500 RPM, where I consistently saw torque limiters in the MHD logs. Overall, there’s no question the transmission has normal wear and tear at this point, even though it’s not slipping yet, which is why I’m still considering servicing it.

As for the fault codes I had, they could be related to a leaking mechatronic sleeve, which we’re replacing as well. Given everything, im leaning towards sticking with oem fluid, I’ll give an update when I service it hopefully this week. 140k miles wish me luck lol.

I think sticking with LG8 is wise. Consider doing a second dump & fill shortly after you do the initial service. Hopefully the seals refresh will help with your error codes. Good Luck!

If all else fails & you have money to burn, then you can always solve the 330 lb-ft max torque rating on the 8HP45 with a performance rebuild.

https://speedlogicauto.com/products/...pr_seq=uniform

[WesamJaber]

Originally Posted by ctcarbonari

Personally, I'd stick with ZF LifeGuard8 (or 9) for the 8HP transmission.
I don't see the benefit in gambling with aftermarket oils on my transmission.

Fluid, in and of itself, is not going to "fix" a mechanical issue. No matter who makes it.

UPDATE**

I’m a bit on the fence but here’s how everything went.

The shop fully drained the transmission and the good news is there were no metal shavings in the pan filter, which is reassuring and makes me feel better about the overall health of the transmission.

That said, I’m not entirely sure the fill procedure was done exactly by the book compared to what I’ve seen online. They only performed one fill rather than a second top off. However, they did fill it with the car running and cycled it through all the gears while filling it. Once fluid started dripping from the fill plug, they put the fill plug back on and job finished.

They also reset the transmission adaptations, which I did not specifically ask for and know can be somewhat controversial. Still, on the drive home, which was about an hour on the highway, the car drove perfectly fine with no issues. Shifts were smooth and nothing felt off. I have not pushed it yet since the transmission is still relearning, but this is my experience so far.

They were able to get about 5.5 bottles of ZF fluid in out of the 7 total, which actually seems pretty decent. Most people I have seen report getting less than that. I am not sure if they monitored transmission temperature during the fill, but given how it drove afterward, nothing raised any red flags yet.

Overall it’s okay so far but only time will tell if I have any issues. Do you think it’s okay the way they did this procedure?

[ctcarbonari]

Originally Posted by WesamJaber

UPDATE**

I’m a bit on the fence but here’s how everything went.

The shop fully drained the transmission and the good news is there were no metal shavings in the pan filter, which is reassuring and makes me feel better about the overall health of the transmission.

That said, I’m not entirely sure the fill procedure was done exactly by the book compared to what I’ve seen online. They only performed one fill rather than a second top off. However, they did fill it with the car running and cycled it through all the gears while filling it. Once fluid started dripping from the fill plug, they put the fill plug back on and job finished.

They also reset the transmission adaptations, which I did not specifically ask for and know can be somewhat controversial. Still, on the drive home, which was about an hour on the highway, the car drove perfectly fine with no issues. Shifts were smooth and nothing felt off. I have not pushed it yet since the transmission is still relearning, but this is my experience so far.

They were able to get about 5.5 bottles of ZF fluid in out of the 7 total, which actually seems pretty decent. Most people I have seen report getting less than that. I am not sure if they monitored transmission temperature during the fill, but given how it drove afterward, nothing raised any red flags yet.

Overall it’s okay so far but only time will tell if I have any issues. Do you think it’s okay the way they did this procedure?

Awesome @ update on this thread! That helps everybody.
And congratulations on retiring some of that "lifetime fluid".

Assuming that the shop brought the transmission temp up into the proper range and held the gears at rpm while cycling thru then it sounds like everything was done correctly. i.e. that secondary fill is the topping off procedure, which, imo, is the critical part of this process.

As for the resetting of the adaptation values, yeah, a highly debatable topic on these forums. I would imagine that over time, your adaptation values will settle back to the same as what you posted earlier. The driving relearn procedure is nearly impossible to accomplish unless you're on a high speed raceway or out in the desert somewhere with long straight aways. The software will do its thing by driving it normally for awhile.

To the best of my understanding, the fluid capacity for the system is ~8.8 liters. So, the service procedure swaps out roughly 1/2 - 2/3 of the existing fluid. FWIW, both times I've had this done this on my transmission about 5- liters were exchanged. 5.5 liters is good, imo.

[WesamJaber]

Originally Posted by ctcarbonari

Awesome @ update on this thread! That helps everybody.
And congratulations on retiring some of that "lifetime fluid".

Assuming that the shop brought the transmission temp up into the proper range and held the gears at rpm while cycling thru then it sounds like everything was done correctly. i.e. that secondary fill is the topping off procedure, which, imo, is the critical part of this process.

As for the resetting of the adaptation values, yeah, a highly debatable topic on these forums. I would imagine that over time, your adaptation values will settle back to the same as what you posted earlier. The driving relearn procedure is nearly impossible to accomplish unless you're on a high speed raceway or out in the desert somewhere with long straight aways. The software will do its thing by driving it normally for awhile.

To the best of my understanding, the fluid capacity for the system is ~8.8 liters. So, the service procedure swaps out roughly 1/2 - 2/3 of the existing fluid. FWIW, both times I've had this done this on my transmission about 5- liters were exchanged. 5.5 liters is good, imo.

Just thought I should update, so the transmission is shifting butter smooth and I have no codes as of now but unfortunately I raced my car against a q50…long story short I smoked him bad but then my transmission gave out and went in limp mode after 5500 rpm like before and got stuck in 8th gear again. I had to restart my car for normal operation again. But weirdly now, I have zero codes from my transmission. I’m not sure what to point to at this point with zero codes. The car runs great outside of WOT runs, every 5500 rpm at wot just makes my transmission freak out and get stuck in 8th. Whats even crazier is I don’t even get a transmission malfunction on my Idrive when it happens, it’s like the trans has a mind of its own. I want to try to communicate with my custom tuner to see if there’s possibly a torque to load miscommunication between the engine and transmission that causes my trans to freak out. Whenever this happens at wot I get a tq limiter 2048. Other than this, it drives like butter.