Will not be able to fill ZF6 trans after servicing

andy_bmw_1965 · Mon Feb 23, 2026 9:11 am

Hello again, a typical maintenance issue...
I upgraded the 93's gearbox today by dropping the pan and replacing the mechtronic sleeves and seals. Seemed like everything went smoothly. I replaced the old pan with a new one and torqued it up to 8 nm following the recommended sequence. However, when it was time to add oil, the excess fluid began leaking out of the fill hole. I am perplexed since I have approximately 6 litres of spent oil but only manage to get 50 millilitres back into it.

Filling up while the engine was not running was the original plan. Get the engine up to temperature (between 30 and 50 degrees Celsius), shift gears, and then switch it off. Keep filling the container until it overflows.

you tried what Google suggested—filling while the engine is running—after the fill failed, but it still didn't work. Got all the way through the gears, but the wheel still won't spin, so I guess it's time to head home.

Do you have any suggestions?

capewell77 · Mon Feb 23, 2026 9:12 am

I find it strange that there is only a hole in the side of the box that goes straight in. Usually, after changing the pan, you can pump roughly 4 litres in before starting. I thought the fill pipe extended a few cm beyond the first aperture; is that correct?

andy_bmw_1965 · Mon Feb 23, 2026 9:12 am

Placing it to its maximum apparent length of approximately 1 cm.

Did I get the right hole? Towards the front, on the left side, you can see it. As far as I can tell, it's the only fill port accessible.

The mechatronic sleeves were securely in place and functioning as they should have been, but one of them kept slipping out. The correct technique was with the square-shaped seal.

capewell77 · Mon Feb 23, 2026 9:13 am

Sure, I can help you with that. The filler is an 8mm Allen key plug on the offside of the box. On the near side, you're peering into a hole.

andy_bmw_1965 · Mon Feb 23, 2026 9:13 am

As a result, the driver's side should be proper? Embraced it if I could see it. Tell me where I can find it.
There was an 8mm thread on a 5mm hex at the location I've been exploring.

andy_bmw_1965 · Mon Feb 23, 2026 9:14 am

Are you saying that I located it close to the bracket for the exhaust pipe? Maybe. Damn, I had that device disconnected in order to modify the macktronics connection.

capewell77 · Mon Feb 23, 2026 9:15 am

So, this is the right one for right-hand drive vehicles; it's the driver's side.

andy_bmw_1965 · Mon Feb 23, 2026 9:15 am

Thanks! I'll take a closer look at it today because I suspect an exhaust pipe hanger is hiding it. Again, my maintenance failure made my wife laugh uncontrollably. I should try to make amends a little.

andy_bmw_1965 · Mon Feb 23, 2026 9:25 am

Take care of it, thank you.
The gear shifts are now smooth as silk, and I can no longer hold on to third gear after adding 7 litres of fuel.

maturo99 · Mon Feb 23, 2026 9:27 am

Although I'm sure you're relieved to have found it, I'm willing to guess that you're not the first person to get it incorrect.
Once you realise you can't refill the box, you'll experience terror.
After my wife would ask me "well why did you start the job?" she would simply leave the room.