I have a 2000 olds bravada awd. If i raise up the rear axle and put it in drive and accelerate no speed is registered on the speedo. But driving down the highway the speedo works perfect. The AWD is also inoperative. I have replaced one of the sensors for the rear wheels and nothing was corrected, so i changed out the second one with the first one and still nothing. Any help would be awesome.

 

Your speedometer problem doesn't seem possible. The VSS sensor is located in the back of the transfer case along with the rear output shaft speed sensor.

Here's an illustration of the sensor locations:


Is your 'Service AWD' light illuminated on the dash? If so, you should get the codes read (takes more than a generic scan tool) since it's trying to tell you what is wrong with it.

One word of caution though, you should never put an AWD vehicle in drive with only one axle off the ground. Very bad things can happen.

 

Thanks for the reply. Both sensors in the back have been replaced. No AWD light is on in the dash. I have been in the automotive for years but only deal with the old fashioned shift on the fly 4wd. Trust me i expected the truck to move forward on the floor jack after jacking up the rear axle.