uptheorg

This morning I had my 1995 Cabrio C4 inspected in New York State. Unfortunately, I "forgot" that it was four-wheel drive and the mechanic put it on a normal, rear-wheel-drive, dyno. The car operated like a rear-wheel drive car while he put it through the routine, running it in fourth gear between 2k and 4k RPM. Suddenly, after about three minutes of this, the front wheels engaged!! Were it not for the safety straps, the car would have taken off and gone through the garage wall!! He managed to burn rubber before the system gave the power back to the rear wheels. Needless to say, we stopped the test right there!

MY QUESTION IS THIS: Why did it take so long for the front wheels to engage? Isn't the four-wheel drive always in effect? What happened here?

Phil

What kind of inspection?

Stuttgart

The awd sends power primarily to the rear wheels, and when there is a differentil in wheel speed front to rear (like putting a car on a rear wheel dyno ), the fluid in the viscous coupling heats up(kind of like a torque converter) and power is sent 40/60 front to rear.

You may have burned up the viscous coupling

If this is your mechanic that knowingly put a C4 on a rear wheel dyno, i would definitely start looking for a new mechanic.

rsrdan

very well written ...stuttgart

uptheorg

I still am wondering about this because the car sat on the dyno running in fourth for over two minutes before the front wheels showed any sign of getting involved! If anything "burned out", there would be an immediate sign as soon as the back wheels started spinning, no?