[Mogsy]

Hey all, I'm new here, so thanks for having me.

This is a long one, sorry. I'm ready to pull my hair out with this issue, so any help/advice would be greatly appreciated.

I've not long bought a 2014 535d with 124K on the clock. (yes I know the forum states 2010 2011), but I assume the gearbox is the same.

There was no history with the car so I promptly had the chains swapped and gearbox serviced. All seemed well after picking it up.

I fitted a straight through downpipe, larger intercooler, egr cooler delete and egr blank, then had the car and gearbox remapped. All seemed well again as the car was totally transformed.

The remap consisted of me driving up and down the road whist logs were taken and changes made. I would have the car in sports manual 4th gear and floor it to redline until it changed gear. This was carried out until we were both happy with the tune and how the car behaved.

I took the car to be rolling roaded to see what power it was producing and this is where the problems began. The tech couldn't prevent the car from changing gear whilst in manual mode and dyno mode.

In 1st, 2nd and 3rd gear it revs all the way to the redline, but in 4th and above it changes at 3500 rpms. I've noticed it does this when oil temp is roughly above 75 degrees. Before this, it will rev past 3500. When warmed up, if I use the kickdown and rpms are above 3500, they'll go all the way to redline in all gears until they get close to 3500 and it'll they change between 7th and 8th over and over.

My remapper suggested having the oil level in the gearbox checked, which I had carried out by the garage that serviced it and they said it was fine. My remapper also suggested there may be clutch slip, but there are no error codes to suggest this.

I took it to another garage as it was suggested to have the quality of gearbox oil checked (as it may be cheap stuff that was used) and also the gearbox seals swapped as they may be leaking and not allowing pressure to be maintained. The garage proceeded to remove 2 litres of overfilled oil (so much for the level being fine!) from the box and advised my ZF8 box only has a figure of eight seal (not the square seals) that won't affect gear change if it's leaking. The car was taken for a test drive and still changed at 3500 rpms after the excess oil was removed.

I noticed on the drive home that it would intermittently rev past 3500 in 4th, so maybe the excess oil was causing it.

It has now been suggested that the excess oil has damaged the gearbox and that I should fit a second hand one and have that serviced to see what happens.

Just to note, the gearbox map was removed in order to test and the issue still happened. I am yet to have the car put back to normal tune to see if it's a torque issue causing it. If it was, I'd expect it to not rev over 3500 and stay there when using the kickdown.

My remapper is also very knowledgeable, so I know it's not a mistake on their part.

Are there any experts out there that have any advice for me, please?

[SWFLf10]

Originally Posted by Mogsy

Hey all, I'm new here, so thanks for having me.

This is a long one, sorry. I'm ready to pull my hair out with this issue, so any help/advice would be greatly appreciated.

I've not long bought a 2014 535d with 124K on the clock. (yes I know the forum states 2010 2011), but I assume the gearbox is the same.

There was no history with the car so I promptly had the chains swapped and gearbox serviced. All seemed well after picking it up.

I fitted a straight through downpipe, larger intercooler, egr cooler delete and egr blank, then had the car and gearbox remapped. All seemed well again as the car was totally transformed.

The remap consisted of me driving up and down the road whist logs were taken and changes made. I would have the car in sports manual 4th gear and floor it to redline until it changed gear. This was carried out until we were both happy with the tune and how the car behaved.

I took the car to be rolling roaded to see what power it was producing and this is where the problems began. The tech couldn't prevent the car from changing gear whilst in manual mode and dyno mode.

In 1st, 2nd and 3rd gear it revs all the way to the redline, but in 4th and above it changes at 3500 rpms. I've noticed it does this when oil temp is roughly above 75 degrees. Before this, it will rev past 3500. When warmed up, if I use the kickdown and rpms are above 3500, they'll go all the way to redline in all gears until they get close to 3500 and it'll they change between 7th and 8th over and over.

My remapper suggested having the oil level in the gearbox checked, which I had carried out by the garage that serviced it and they said it was fine. My remapper also suggested there may be clutch slip, but there are no error codes to suggest this.

I took it to another garage as it was suggested to have the quality of gearbox oil checked (as it may be cheap stuff that was used) and also the gearbox seals swapped as they may be leaking and not allowing pressure to be maintained. The garage proceeded to remove 2 litres of overfilled oil (so much for the level being fine!) from the box and advised my ZF8 box only has a figure of eight seal (not the square seals) that won't affect gear change if it's leaking. The car was taken for a test drive and still changed at 3500 rpms after the excess oil was removed.

I noticed on the drive home that it would intermittently rev past 3500 in 4th, so maybe the excess oil was causing it.

It has now been suggested that the excess oil has damaged the gearbox and that I should fit a second hand one and have that serviced to see what happens.

Just to note, the gearbox map was removed in order to test and the issue still happened. I am yet to have the car put back to normal tune to see if it's a torque issue causing it. If it was, I'd expect it to not rev over 3500 and stay there when using the kickdown.

My remapper is also very knowledgeable, so I know it's not a mistake on their part.

Are there any experts out there that have any advice for me, please?

From my experience, you can't really overfill the ZF8 transmission… If anything it's easy to under fill since you have to warm up the transmission to fill it completely while running with the wheels off the ground. If you don't warm it up via the correct procedure then you end up being low on fluid. Not sure about the issue, but my 2¢ is the transmission fluid level probably wasn't an issue to begin with.