Okay, looks like I started something that is being blown out of proportion, not only by myslef by others also.

In response to DavieGravy's last reponse, I can tell the young man is confused. When you go back and read the previous posts, I can understand why. I think I too, would be confused.

My question, (I thought) asked if there were two sets of rollers. That would mean four drums, right? If I am wrong, someone please correct me.

The observation I made referenced the way vehicle emmissions were tested in the Lone Star state. I've never seen a double set (my words) of drums, wherein front/rear tires each sit within a drum assembly that contacts each side of the tire patch. They don't have these in Texas, at least for emmissions checks. The inspection tech informed me that if the vehicle was AWD, then they conducted an RPM test (one low, the other high with a sniffer tube). If there is another state using a double type roller system, i.e. four drums, then I would be curious as to how the test was conducted. That's all I was curious about.

Davy, yes, all the tires/wheels must turn in the same direction. If they didn't, I wouldn't want to be in the same facility. Kinda like having the front axle in a forward speed and the rear axle turning the opposite direction. That can't happen. At least on any AWD I am aware of.

The dyno question is a little harder to answer. My understanding: this machine is used to measure horsepower, torque and braking force. Could a dyno with a front and rear axle setup be used to check SVXs, yes. Dyno's can simulate load, drive angle (degree of slope), force created by the vehicle drivetrain, etc.

Didn't mean to confuse anyone, just curious about other states and how they test AWD vehicles.

Hope all of this info is a little more clear/precise. If not, send me a PM and we can go from..........

Mike