[emanuelxcars]

As the title states I am having some issues filling up my ZF8 transmission after the service. I ordered the ZF pan and lifeguard 8 fluid from FCP and followed all their steps to a T. The car drives fine in comfort and shifts are perfect and silent in comfort and sport+ no matter how hard I accelerate. (N55 MHD Stage 2+ 70k miles)

My issue starts once the transmission reaches 75C, because that's when accelerating hard in gear 1 and 2 create a very loud supercharger like whine. From what I've been reading, at 75C the thermostat for the oil cooler opens up.

I know that they mention to overfill the transmission by 0.5L when doing the initial fill but I find that very hard to do because the more I fill it the more liquid drips out. It's almost impossible to overfill it. I was wondering if there is any tool or grommet that can be put in the fill hole to allow for that additional 0.5L to be added on... or do I have to just keep pumping the fluid in faster than it's coming out and then quickly put the fill plug on.

Realistically even after driving it, letting the trans reach 75C so the valve can open and then letting car cool off... the valve would still be open after I shut off the car since it is above the 75C threshold and the fluid would drain back into the pan, in turn not letting me overfill.

Is this just bad design or am I missing something? Is it normal for the gearbox to make those noises especially only after the trans reaches 75C (possibly confirming my suspicion about low fluid).

[BlueberryPie]

I just went through this after changing my fluid around 54k miles. I was also experiencing the supercharger whine before changing the fluid, but much less frequent - usually only one time after some spirited driving.

After some digging around I found a suggestion to tilt the car up from the passenger side - so the fill plug side of the transmission is higher and the fluid won't leak out. Of course the engine needs to be running and between 40-50 C during the final fill, but that worked for me (make sure the car is safely supported). I kept the driver's side wheels on the ground and had plenty of room.

Now I did all of this a few days ago and guess what...I still hear the supercharger whine in 1st/2nd at full throttle after the transmission reaches 75 C like you, though maybe not quite as loud anymore. Hoping as I put more miles on the car it will go away.

I've yet to read a post where someone had the whine issue lead to a failure of the transmission and I don't think many people even know about the step to add the extra 0.5L so I'm trying to tell myself not to worry too much.

[Nickies]

FCP has a detailed tutorial on the ZF service. There is no mention of an overfill to be done. After the second fill up, you have to let it drip and put the plug back and it is completed.

I am at 63K and drive moderately. I don't see a rush to have this service done. I will definitely go to a reputable transmission shop and i will have a warranty if something goes wrong.

[BlueberryPie]

Here's a document from ZF that includes the chart below: https://aftermarket.zf.com/app/contr...505690da53.pdf



I stumbled upon this video by WeberAuto - he has multiple videos about the ZF transmission and goes into detail about them. Check out the clip around 11:56 - "Additional fluid may need to be added due to the cooler thermostatic bypass valve" -

It's hard to ignore that the cooler bypass valve opens at that very same temperature I start to hear my transmission make the "supercharger" whining noises (75 C), just like the original poster described. Am I just underfilled? I hate to add anymore fluid at this point.

[Nickies]

Call Customer Service.

Technical Support: Call (855) 228-3203, option 1, or email NAcustomercare.zf@zf.com for technical support.

[tbuck]

I guess I am missing something. The process, as I have always done it on these and other newer transmissions, is first fill, run system until up to full operating temp and then top off while the engine is running. If you turn off the engine or wait for it to cool the level in the pan will be too high to add more to, so it has to be running and at full temp. I don't think you can "overfill" a specific amount as it is running out all the time. That does not make sense. And generally the needed amount for the second fill is more than .5 liter anyway.

[XutvJet]

Assuming the trans wasn't leaking and was performing normal, why don't people just drain the ATF on a completely cold trans, measure exactly what comes out, and add cold fluid back in?

[tbuck]

Likely because that is not the correct process. I would prefer to follow the manufacturers process. Better that way.

[LA1Z24]

Overfill the transmission by tilting the vehicle forward. jack up the rear, and keep the front lower than the rear. That will cause the fluid to slosh forward, away from the fill/level check port.

[ClassicFlash]

Apologies for bumping an older thread. When ZF indicates "Drive the vehicle until the valve opens," do they actually mean drive the car (on the road), or do they mean let the engine run to reach >75c temp fluid (while the car is still lifted)?

Then it appears that we are not supposed to turn the engine off but "Allow the fluid to cool down" below 50c.

Any tips or tricks?

[myuji]

I’m planning to do a fluid change and ordered a OEM ZF pan, the QR code in the box points to the same documentation.

After reading the doc I believe the 0,5l overfill is misunderstood and you shouldn’t have to leave it overfilled. Let me explain.

The flowchart sparks the 0,5l overfill concerns ends with “Go to [1]”, which references the [1] mark of the next page, which ask you to perform the typical “fill until oil drips from filling hole” flow.

So even if you have successfully overfilled (and it stays overfilled) to begin with, the overfilled oil would have dripped out in this step anyway.

The flow with overfill with 0.5l also have the interesting “e.g. after a repair” remark, which makes me think the purpose is such that there are enough fresh oil to fill the oil cooler in case it was drained, and not because it is supposed to be overfilled.

(Edit: it also means you just an try your best to overfill up to 0.5l during initial fill, drive it up to 75c so it fills the cooler, wait until it cools down to 30c, and proceed to normal filling, worst case you’ll be underfilling 0.5l during the time getting the cooler open)


Make sure that the temp of the transmission is about 30-50c, with engine running, and really pay attention to leveling the car and you should have a good fill level.

[MarcoZandrini]

I am so glad my car has a manual transmission!!

[Nickies]

I went to a small reputable BMW shop for transmission service. The tech is BMW Certified.

I paid $1.2k including differential but I have complete piece of mind. There is no way I would have gamble to potential problems just to save a few hundred bucks. When you own a BMW, you have to pay to play.