[b58shah]

Hi BimmerForums, i’m currently debating when to do my transmission service and differential service on my 2019 BMW 440i xDrive MPPSK at my current mileage. I bought the car at 54k miles and it is now at 56k miles. I drive quite spirited and I know previous owner also drove it pretty spirited. It’s never been tuned, only catless downpipe + mppsk (m power kit) for about 22k miles.

Here is the maintenance I know of on the vehicle so far:

- Last Oil Change done at 54k miles (0w-20) I live in a cold climate.

- Engine Filter at 54k miles

- OEM Sparkplugs at 55k miles

- New Battery at 56k miles

-Transfercase and Driveshaft replaced at 37k miles through warranty (not sure if diff service was done)

Here are the current issues of the car that i’m having:

1. - DME active codes:
128301 - Oxygen sensor before catalytic converter, signal: fixed at rich.
12AD01 - Oxygen sensor after catalytic converter, signal: fixed at lean.
(The rear 02 sensor code is normal due to being catless without a proper tune, but the front 02 sensor isn’t normal, inspection said that my front 02 sensor was touching the exhaust manifold so I may have damaged the upstream 02 sensor causing this code and car feels sluggish very low RPMS on highway)

2. Issue (Not really an issue just transmission fees weird)

Whenever car shifts from 1 -> 2 or 2 -> 3, it’s quite jolty, from what I was told ZF8 is supposed to shift smoothly. I know it’s recommended by ZF8 to do it every 50k miles, but I want to see if I should do full trans fluid or just drain and fill.


Im planning to go MHD Stage 2 after all the preventative maintenance is done, but I want to know whether I should do the full trans service since i’ve heard people get transmission issues after doing the full service. I really don’t want to waste extra money on doing unnecessary maintenance right now as I am still financing the car and would prefer to do it after it’s paid off, but I also don’t want to run into any expensive repairs in the future.

If anyone has any advice it would be greatly appreciated.

[Tommy D]

If you drive like you say, I would say Yes, and replace the fluids in the Diffs. At the same time the shop can check for leaks. Cheap insurance and piece of mind.

At your mileage other drivers have reported while changing the diff fluid it had a dark brown color and most enthusiast say to replace around 40-50K miles anyhow.
Also too many drivers are experiencing leaking at the diffs on the F and G series cars and if you don't notice it soon enough and the diffs start making noise, it's replacement time. They only hold about a quart of fluid. A friend of mine started to hear a noise from the rear of the car on acceleration. We found the rear diff was wet and the leak not identified the last time it was in the shop, plus he wasn't under the car during the winter. Needless to say, the diff was shot, and I will tell you it is $$$$.

As far as the transmission, ZF recommended 60-80K miles before replacing the fluid but some change sooner. I replaced my trans fluid and filter at 70K, but I am anal about changing the fluid regularly, as I ended up replacing a transmission in my youth and don't want that expense again.
Others complaining about transmissions shifting due to a fluid change are ones that waited too long and the internal parts are worn.

Hope this helps.

[cfm56d7b]

At approximately 50K miles, it’s far too early for ZF transmission to shift abruptly in early gears.

The dilemma: transmission are sealed units and BMW does not repair transmissions. The dealer replaces transmissions. I suggest to find a shop that can properly diagnose the issue and at the same time replace the fluid.

Abrupt shifts point to a few potential issues:

- Old fluid can reduce clutch engagement so the shift is more abrupt
- Valve body is a very complex component. Sticking valves (dirty fluid is often the cause) will change hydraulic pressure

The best course of action is not to delay the diagnostic efforts if you plan to keep the car.

[b58shah]

It may just be me but whenever shifting from 1-2 or 2-3 in Sport+, it feels new to me but not odd. Not sure how to explain it. It’s a small jolt like my head still bops a bit. But I feel like it’s normal especially with the M Power Kit tune and a faulty upstream 02 sensor.

[Wires]

Does it shift fine in comfort? Previous owner might have tuned the transmission with xHP. That would explain the harshness.

Do you only feel the jolts at high throttle loads?