Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

ZF Automatic Transmission

Hi CarTalk Community,

I have a bit of a problem here and I hope that my question is not out of place.

I want to construct a Lepelletier automatic 6 speed gearbox. I want to create a 6HP19 with the following (standard) ratios: 4.17 - 2.34 - 1.52 - 1.14 - 0.87 - 0.69 - 3.40 - -3.73

I found the dimensions of the gears on that page:

However, as you can see, the short planetary gears are bigger than the long ones, which is a problem because I cannot place the ring gear around them, as it is shown here on page 8:

So, this question is probably a bit awkward, but I hope someone can help me :slight_smile:

Best wishes,

I am not entirely sure what you are asking. Are you starting with an existing transmission and rebuilding it? If the parts won’t fit, you’ve done something wrong.
Are you modifying the transmission’s ratios? Where did you get the parts?

Page 8 clearly shows the short planetary gears as shorter than the long ones… so what do you mean by “bigger”? In diameter?


Thanks for your answer. I constructed the parts according to

There, you see that the short planetary gears have a larger diameter, as you say. But, I need the diameter to be shorter. How do I do that? How can I calculate the gears? :slight_smile:

Best wishes,

Then the circle locating the centers of the short planets must be smaller than the circle locating the centers of the long planets.

Thanks for your answer insightful, but your answer does not make any sense :slight_smile:

Ok, here is (perhaps) a simplified question to the question above

I have the following gears:

What do I need to do to lower the number of teeth of the gear in the
center (light blue) WITHOUT changing the position of the left and right
gears (dark blue)? The gear in light blue is the only that can be
modified (position and number of teeth)!

Best wishes,

Would a sympathetic engineer at ZF ,perhaps help? ,sounds to me like you are constructing a "Franken -mission "

You can’t without changing the location of the gear axis.