A nice explanation of the ZF 9 Speed

Excellent read!

My faith and understanding has been restored as I now understand the reason for the abrupt shifts in low gears due to the dog clutches. Well worth reading.
I just hope the 9 speed transmission is reliable, as some of the early ones are due for a recall (due to park engagement).
It also explains why I've not yet seen 9th gear.

Thanks for posting this. A good and informative read. Enlightening.

I can't believe I missed this post. It's an interesting read on what is going on with the 9 speed.

You know...I used to see the hard 2/3 shift as a nuisance. Or rather I should say it was annoying because I was always anticipating it. I've had the car for 3 months now and I drive it almost everyday. I've either gotten used to the hard shift, it's really not that bad in general and I was just influence by all the post I've been read on TLX forums.

To simply put. I love everything about my TLX.

I just read that website as well. Didn't know the ZF 9HP had such a problem. Kind of shocked to see that the ratios are like that, having 5th as the 1:1 ratio instead of 6th. Why bother making a 9 speed automatic if we can't utilize it to the full potential? I wonder why Honda didn't use the Aisian 8 speed automatic used by Volvo.

I'm trying to understand what the author wrote and I have an idea idea on how the automatic transmission works now. However that doesn't explain the rougher 2-3 upshift does it? Since 2-3 uses the traditional friction brake and clutch elements, whatever that is. That's the only rough shift I can feel. Everything else felt good I think? Also according to my friend, this means the ZF 9HP would never shift as smoothly or rapidly as the 8 speed DCT developed by Honda or Aisin 8 speed automatic for example?

Edit: Car and Driver Explores the ZF 9HP as well.

Wondering if the hard shifts could be related to a heavy foot on the gas? I find the throttle to be more on the sensitive side and can see light occilations of the pedal cause some transmission fluctuations.

Alex does a fantastic job on explaining the 9-Speed Transmission

https://www.youtube.com/watch?v=Z7EMGnjEhmE

So how come gear 2-3 is so "rough" if it doesn't involve the dog clutches? That's the only gear shift I find that is not very smooth while all other 8 gear changes are pretty smooth overall.

geokilla said:

So how come gear 2-3 is so "rough" if it doesn't involve the dog clutches? That's the only gear shift I find that is not very smooth while all other 8 gear changes are pretty smooth overall.

Click to expand...

THAT is the million dollar question!

It is likely rough, under some conditions, because the intelligent learning system (transmission and software) was not able to coordinate the timing of brake (in the transmission), clutch, and shift elements perfectly. It needs to be able to do this under a variety of conditions:

- load on the transmission (final drive)
- RPM (increasing, steady, or decreasing)
- temperature of the transmission (hydraulics) and slip point of the clutch
- determined shifting point
- possibly other factors

It is a complex juggling act to get it right for the combination of all conditions. It is likely just a software issue, and it should be possible to eventually get it right. But there could be constrains on the speed and capacity or the processors involved that limit handling every condition (speculation on my part).

The answer is academic though, as the driver just wants a perfect shift every time and should not have to care about the difficulty involved in its implementation.

Does anyone know why Acura didn't use the ZF 8-speed transmission instead? I'm not sure how big of a fuel savings there is going from 8 speed to 9 speed. My wife's BMW X3 has the ZF 8-speed and it's by far the best automatic transmission I've ever driven. Like many of you on the forum, I leave my TLX in sport mode for more responsive shifting.

Marketing the newest tech, better fuel economy, prior engineer dollars commitment, who knows. No complaints with my 9 especially after the updates.

geokilla said:

I just read that website as well. Didn't know the ZF 9HP had such a problem. Kind of shocked to see that the ratios are like that, having 5th as the 1:1 ratio instead of 6th. Why bother making a 9 speed automatic if we can't utilize it to the full potential? I wonder why Honda didn't use the Aisian 8 speed automatic used by Volvo.

I'm trying to understand what the author wrote and I have an idea idea on how the automatic transmission works now. However that doesn't explain the rougher 2-3 upshift does it? Since 2-3 uses the traditional friction brake and clutch elements, whatever that is. That's the only rough shift I can feel. Everything else felt good I think? Also according to my friend, this means the ZF 9HP would never shift as smoothly or rapidly as the 8 speed DCT developed by Honda or Aisin 8 speed automatic for example?

Edit: Car and Driver Explores the ZF 9HP as well.

Click to expand...

I should have read the C&D link geokilla posted. It answered why they didn't use the ZF 8HP. ZF 9HP was designed for transverse mounted engines like the one found in the TLX vs the ZF 8HP designed for longitudinal mounted engines commonly found in RWD BMW's.

I appreciate the article very much. It relieves some of my concerns. I have found that I can minimize the 2nd to 3rd shift by simply keeping a light foot on the accelerator. It is not 100%, but is much smoother. I have to admit that I use Econ more than any other mode. It is a bit more pronounced.

I noticed that because the ZF 9HP is so slow to shift, I can occasionally get it caught out on a 3rd to 2nd or 2nd to 1st downshfit. I'm unsure what gear it's in when I catch it make a mistake but basically I'm coming to a slow, slow speed (5Km/H?) then I accelerate like I normally would because traffic ahead is picking up speed again. During acceleration, the transmission will basically slip then downshift as the transmission tries to deliver the power to the wheels. Then it'll finally accelerate as you can clearly feel the shift in G forces.

Update:

My 2-3 shifts are almost GONE/Undetectable. I have been doing some 'bat out of ****' style driving a few times, and two long road trips.

Nascart said:

Update:

My 2-3 shifts are almost GONE/Undetectable. I have been doing some 'bat out of ****' style driving a few times, and two long road trips.

Click to expand...

*jealous*

Want to trade cars?

some of earlier ones are postponed and are due to recreation area engagement. It's kind of describing why i haven't seen 9th shift.