This guide applies to BMWs equipped with both ZF6 and ZF8 transmissions. This procedure is not for filling the transmission after installing a new transmission or working on the oil cooler. In case of replacing the transmission, you’ll need to flush the oil cooler, which requires additional steps.
If you want to get right to the procedure, here are some PDF guides to help you:
Otherwise, keep reading.
Let’s get started.
Parts: Automatic Transmission Oil And Filter
Both the transmission, transmission oil, and transmission software are developed together to specifically match each other. The sole oil supplier for ZF6 and ZF8 transmission oil is Shell. That means that both the BMW ATF2/3+ and ZF LifeGuard6/8 are the same oils, respectively.
So, here are the oil specifications for each transmission:
|ZF6HP||M-1375.4||ATF 2||LifeGuard 6|
|ZF8HP||L-12108||ATF 3+||LifeGuard 8|
Now, you might have heard that you can use LifeGuard 8 for ZF6 transmission, but not so. Although the LG6 and LG8 share the same base and are exactly the same oils, the LG8 contains the additives that LG6 doesn’t. So, for LG8 to work properly in ZF6 transmission you’ll also have to change the EGS software.
This conversion was actually used by Audi with some ZF6HP19A and ZF6HP26 transmissions to solve the shudder issue. For BMW, there’s no software upgrade to LifeGuard 8.
Besides the oil, you’ll also need the oil filter, which is integrated into the oil pan. You can opt for a genuine BMW part or ZF Aftermarket one.
In my opinion, the best option is the ZF Automatic Transmission Service Kit.
Can Oil Change Damage The Transmission?
Contrary to what most people will tell you, yes – transmission oil change can ruin your transmission easily. As I’ve talked about extensively in this article, there’s a greater chance to ruin your transmission by changing the oil than leaving it, as BMW recommends, for the lifetime of the transmission.
Now, I don’t want you to get me wrong, so let me explain.
There are basically three reasons behind this phenomenon:
- Lack of oil because of not following the procedure, for example skipping the ‘filling the torque converter’ step, or any other.
- Wrong oil because people want to save money and think they are smart.
- The transmission is already damaged but the owner hopes that fresh oil will fix it. Instead, the fresh oil only accelerates the inevitable.
Can Transmission Oil Change Fix Harsh Shifts And Shudder?
It can happen, but it’s not something you can bank on. Transmission oil friction modifiers lose their properties over time, depending on how you drive, and when adaptations cannot compensate for this loss, you get – a harsh shift and/or shudder.
When you change the transmission oil, these properties are partially restored, and the transmission may shift more smoothly.
These issues were more common with GM5/6 Hydramatics and early ZF4HP transmissions. In fact, BMW once had an official fix for the torque converter shudder and harsh shifts by adding a special additive (GM6 Top-Treat CC) to transmission oil.
It’s often a hit-or-miss tactic.
So, before you try to repair your transmission with an oil change, you might want to try some of the additives first.
Drain and Fill or Flush?
With flushing, you’ll replace most of the oil, if not all; with the drain & fill method we are talking about changing about 60 to 70% of the oil. That’s why I like to call this method refresh instead of change. I can talk about the pros and cons of each method for days, but trust me, you don’t want it.
Instead, I’ll tell you straight that drain and fill works just fine and is more than enough to keep your ZF transmission in perfect shape. Besides, this is the method that both BMW and ZF recommend.
However, if your transmission is filled with a bit of the wrong oil, you’ll have to flush it. Flushing the transmission because of the wrong oil actually happens very rarely, because the transmission is usually already damaged.
If you opt to flush, the best method is to use a Hot Flush machine. When flushing, you should use A LOT of CORRECT oil, which is pricey. As a result, most shops use some generic oil for flushing, which will inevitably contaminate the final fill.
Before Changing The Oil
To prevent wasting money, you should first determine whether changing the oil even makes sense. The sole purpose of changing the oil is to maintain transmission health. Fresh oil cannot supply new friction material to worn clutches, repair pressure solenoids, weld cracked adapter seals, or replace worn-out clutch E bushings… You see where I’m going with this.
In fact, fresh transmission oil will often accelerate the inevitable: total failure.
The car’s mileage here is as helpful as the boat’s engine running hours – not at all. The most important factor in both cases is operation conditions, so forget about mileage.
Fortunately, evaluating the state of an automatic transmission is relatively simple – these two conditions must be met for an oil change candidate:
- Flawless operation
- Healthy adaptation values
The first one is obvious, if transmission shifts smoothly – it must be good. The best tester is you, the driver. While driving you can feel how the transmission works – you want smooth shifts, no RPM fluctuation at a constant speed, neutral idle control works fine (when you put in D RPM stays the same), and no kicks from behind when coming to a stop… both with a cold and warm transmission.
With a perfectly functioning transmission, all we want to know is how much life is left in it. You’ll need ISTA or another scanner capable of reading adaption values for this. With a scanner, you can check the health of the five clutch packs.
You want these readings:
Clutch fill pressure adaptation: -350 to +350 mBar
Rapid fill times adaptation: -120 to +120 ms
While these are the values of a healthy transmission that can drive for another 100,000 miles or more, the majority of them will perform OK up to -700 to +700 mBar offset values, but these transmissions don’t have much life left in them.
If you want to dive deeper into transmission adaptations, in this article I covered the topic extensively.
Now let’s have a look at a real-world case.
Look at these adaptations from a 2013 BMW F10 530d with ZF8HP70. This is what an excellent candidate for an oil change looks like:
This is the transmission with 150,000 miles without an oil change. This tranny shifts like a dream without any issues whatsoever throughout its lifetime. As we can tell from adaptation readings, both pressure and time values are well below concerning.
So, if the readings are below +/- 350 mBar for pressure adaptations, and +/- 120 ms for rapid fill times, you are good to go.
With the same driving style and in the same operating conditions, my guess is this transmission will last for at least 100,000 more miles. So, here the oil change makes perfect sense.
Dark brown to black burnt oil usually indicates that the transmission overheated and burned the clutches, particularly the renowned clutch E pack.
If the oil is heavily burnt but the transmission functions properly, it might be wiser not to change the oil. Just check and adjust the oil level. The worn oil is filled with particulates that actually help with sealing and clutch friction.
Now, changing the burnt oil on rare occasions can actually help, but you’re just kicking the can down the road.
If the oil is yellow or green and doesn’t smell burnt, you don’t need to change it.
Before changing the oil
The automatic transmission’s oil level can only be adjusted if the following requirements are met:
- Idle speed should be between 550 and 900 RPM
- The temperature of transmission oil: 25-35°C (initial fill)
- The temperature of transmission oil: 35-45°C (oil level adjustment)
- Even when the weather is scorching hot, it is necessary to monitor oil temperatures. In extreme circumstances, the transmission must be allowed to cool overnight.
If you have an ISTA application available, just follow the service function for the oil level to the letter. This is the best and most reliable way to change the transmission oil.
If everyone followed this procedure there wouldn’t be stories about broken transmission after an oil change. Sorry, but I can’t stress enough how this is important!
If you don’t have access to ISTA, you can use any other scan tool to read out transmission oil temperature.
The Importance of Correct Oil Level
Correct oil and correct oil level at the end of the procedure are the two most important factors you want to remember. And the risks come with both overfilling and underfilling.
When you overfill the transmission, the oil rises up to the rotating gears, which slam through the oil foaming it up like a milkshake. When the oil filter sucks up the foamed oil, the hydraulic system has an airbag.
When the transmission is underfilled, which is more common, you face double trouble. First, less oil heats up faster, resulting in a higher temperature.
Although a properly filled ZF transmission can handle a racetrack without difficulty, a transmission that is underfilled by only a quart of oil can struggle even under normal driving conditions.
Strong acceleration forces the oil to the back of the oil pan, allowing the oil pump to suck only air. The same can be stated for hard braking and maneuvering around corners.
Resetting the Adaptations
After a transmission oil change, there’s no need to reset the adaptations. While there could basically happen nothing wrong with it, if there’s a change in shift characteristics, they will be adopted faster if you leave the adaptations.
The goal here is to reduce the adaptation time as much as possible. Depending on the condition, the transmission may normally shift very harshly for about 50 to 100 miles during the adaptation period. And abrupt shifts put a greater strain on transmission internals.
For example, if the transmission requires a +500 mBar adaptation offset for clutch A with new oil, and the adaptation value for that clutch was +450 mBar before the oil change, the transmission control module (EGS) now only has to cope with 50 mBar difference. However, if the adaptations are reset to zero, the EGS will struggle significantly more to attain a 500 mBar offset.
Leave a Reply