BSF

Hello group,

First post here on the board.

Has anyone ever heard of a way to temporary disable the front wheel drive portion of a C4?

I have a Dynojet chassis dyno, and have recently gotten the itch to be able to run my C4.

I'm looking for ideas on the easiest way to disable the front wheels, whether it's temporary removal of a piece of the driveline, or wondering if the electronic controls (if overridden) have enough authority to "turn off" the front/rear differential.

Thanks in advance for the input,
-Brock F.
Asheville NC

gjvander

Adrian can probably give you more info, but I think the standard way to do a dyno run on C4 is to disconnect the longitudinal drive shaft at the aft end. Two bolts - pretty easy to do.

Regards,

Geo

Adrian

What you see on the outside is the torque tube. The drive shaft actually runs inside the torque tube. Sliding the drive shaft out of the front diff and removing it from the power transfer unit (front of the transmission) is certainly not difficult but it is more than 2 bolts.
However I do not recommend this course of action. Why? The transmission may overspeed due to the reduced load. Remember it is designed to power the front wheels ALL the time. If you remove this load who knows what is going to happen. I would also doubt the figures generated as well.
Find a dyno which has a set of unpowered rollers up front or use an AWD dyno.
Ciao,
Adrian
964C4

PS: If you do go down the disconnect route please also remember to disconnect the PDAS/ABS control unit. Failure to do so will result in other problems.

wjk_glynn

Here's a list of Dyno manufacturers: http://www.weissach.net/Suppliers_Dynamometers.html

From their, you can locate shops that have their products in NC.

Karl.

BSF

Thanks for the reply... I guess my original post wasn't clear enough. I didn't mean that I had ACCESS to a Dynojet dyno... I OWN a Dynojet dyno. So obviously, the motivation is to use my own dyno instead of hunting down and paying for services on somebody else's AWD facility.

I just find it hard to believe that nobody else has ever done this before...

My biggest concern is exactly what you touched on... What will the electronics and/or inner workings of the power transfer unit do with the information that the rear wheels are turning and the front wheels are not?

Adrian, could you give a brief description of how the power transfer unit works? How does it split power between the front and the back? Are there any road conditions that call for it to send 100% to the back? (such as the front wheels losing traction and slipping)

Thanks again,
Brock

pzull

My Mechanic tried it before on my car, didn't work.

He tried it on a 993 and it worked.

He checked the 964 manual and gave me the reason, but it was too technical to remember