2002 C4 with automatic trans w/ tiptronic, 51,000 mi. On board computer indicates the wheels are out of sync. On normal take off, the transmission up shifts too soon. The car makes a droning sound similar to " lugging"? At that point, I used the tiptronic to shift manually.
The car shifts fine with with tiptronic. Trans fluid level is ok. Before I go to the dealer, any thoughts What would cause this?

 

do u have the correct sized rims and tires as specified by Porsche or maybe there is something wrong with front differential....low fluid, etc.

 

Thanks for your reply. Original wheels. Wheels have been trued. 4 Brand new Pirelli tires. Doesn't the front differential draw fluid from the the plan ?

 

I have a manual tranny, the front diff. takes a different fluid that the 6 spd....not sure about an automatic.....id think a front tranny is the same in both tranny versions...maybe someone can chime in..

 

I haven't heard of this issue. It sounds to me like something that could be caused by using tires that aren't the recommended sizes. They have to be within 3% of each other (front to rear) in terms of wheel/tire diameter.

 

Sounds logical.

 

This is only the second set of tires. Porsche spec Pirelis. I'll try to check the front differential today. I'll post my findings. Thanks

 

What sizes are the tires?

 

This is the key question. They may be Porsche Spec but may be the wrong size.

 

do u have different tire brands front/rear or maybe a mixture of new and older tires front/rear...it has to be something with the diameter of front/rear tires..keep us posted

 

Less than 1000 mi on Pirrelis. Front 225/40 ZR 18 N4 Rear 285/30 ZR 18 N4
Not able to check front differential today.

 

u could go to tire rack, look at that tire under specs ans see if the height is similar

 

I looked up your tire brand/sizes and they are .99% close, well under 3%latitude..I dunno but curious...

 

Interesting. I wonder if one of your front differential bearings is beginning to fail and that could be causing it...

 

Maybe check your wheel sensors and splined hub for any damage or corrosion. Did you either run over anything recently or drove through mud or debris?