Hello

I just purchased a 2008 Cayenne S and noticed it rolls forward when reversing on a hill. There was a post back in 2008 from someone with the same problem but no resolution.

Is this normal or is this something I have to take the car back into the shop for?

Any input is greatly appreciated.

 

I believe the hill hold prevents the car rolling backwards if your facing up the hill.
Don't think it prevents the car rolling forward if your reversing up the hill.
Hill hold function is available when transmission is in Drive.

 

My 06 CS with hill holder works fine in drive doesn't work in reverse.

 

lol...

I guess the 'rolls forward' term is relative to who says it.


The way the feature is intended to work is if the car is in drive mode, and coming up to a stop sign/sight on an elevation (front of the car is higher than back of the car). The assumption here is that if the car was put into neutral at such a light, the car would roll backwards to the bottom of the elevation.
The feature is designed to prevent the car from rolling back if driver lets go of the brake pedal (without pressing gas pedal).
This way, if someone stops too close to your rear bumper, will not be hit by your vehicle rolling back.
This feature is adjusted with the service hole on rear rotors. If you search through the DIY sections of this forum and renntech, you will find DIY for replacement of rotors, and also info on adjustment of this feature (I Know I made a DYI about it and made sure to have the info in it).
Do the search and ask more questions if needed.

 

The hill hold is a function of the tiptronic transmission.

It has nothing to do with the brakes.

 

if it is, why would the info for servicing the brakes talk about the adjustment that helps the roll back function? Trying to understand.

Thanks.

 

Can't understand the question. Stopping on a hill - the hill holder allows a brief delay when moving your foot off of the brake as you accelerate uphill. It would not be needed backing up uphill. If you take your foot off the brake, facing downhill, you will naturally move forward - as would be required to drive off. There's no reason to need it if facing downhill - that's what your emergency brake, and brake pedal are for. Even in San Francisco.

 

Hillholder Function Operation.

With the vehicle stationary and the selector lever in “D” or “M,” the Hillholder prevents the vehicle from rolling back on hills without using the brakes.
The Hillholder makes restarting on hills easier.

Operation:
Due to its construction, the Tiptronic transmission in the Cayenne cannot roll back in shifted 2nd and 3rd gear, since a shift element, the one-way clutch acts against the transmission housing and the transmission is thus locked in the reverse direction.

Since the vehicle normally starts off in 2nd gear, this design assists starting on hills.

When stopping, the vehicle always comes to rest in 2nd gear automatically. Using the tap functions on the steering wheel and at the selector lever, the driver has the option of selecting another gear than 2nd gear for starting (1st or 3rd gear). If the transmission were tapped down into 1st gear without applying the brakes, it would cancel the locking function and the vehicle would roll back.

The Hillholder function detects, from the grade and the driver’s power requirement, whether the vehicle would roll back or not if it were downshifted into 1st gear.

If the vehicle would roll back, the tap-selected 1st gear is shown in the display, but the transmission remains in the reverse-locked 2nd gear.

Not until power at the wheels is great enough to start on this grade in 1st gear does the downshift take place. Power and the downward pull of the slope are in equilibrium, and when accelerator pedal value increases, the vehicle starts on the grade in 1st gear.

Source is from Service Information Technik

 

...thanks for the info above, and here is info I found straight from the Porsche brochure about the hill hold feature: see the pic (captured to show)...

 

....and that'll be for a manual tranny.

Here you go, straight from the Service Information Tecknik publication.

Porsche Drive-Off Assistant (PDOA) Cayenne, Cayenne S Drive-off Assistant on vehicles with manual gearbox.

If the vehicle is fitted with a manual gearbox (only Cayenne and Cayenne S), the Porsche Drive-Off Assistant supports the moving off process uphill. This applies whether driving off forwards or in reverse.

The following preconditions must be met:

• The vehicle must first be parked with the brakes (service or parking brakes). If the vehicle only freewheels to a halt, the PDOA is not activated, i.e. the vehicle is not prevented from rolling back as on the Hillholder (only on Tip- tronic).
• The clutch must be operated and a gear engaged. If the gear is disengaged and the clutch released, the brake pressure is released and the vehicle rolls independently.
• The engine must be running.
• The vehicle must be on a definite incline.

If all these preconditions are detected by the control unit, brake pressure is built up at the front and rear wheels through the “active brake servo”.

On driving off, the braking torque is again reduced in relation to the driving torque present.