Good evening gentlemen. I have a 98 Buick Park Ave Ultra with a 3800 Series II supercharged engine. My daughter started driving it not long ago. She is a single mom with 2 kids. Her "Check Engine" light came on and she had it checked out. According to the code it was the speed sensor. The dealer said that the speed sensors needed to be replaced and it would cost around $2800.00. I had she bring the car back to me and I would check it out. I put it on my neighbor'* computer and got the same code. I took the vin number to the dealer and found that it had 2 speed sensors, an input and a output speed sensor. I ordered both sensors. One was small and the other one was a little larger and had a O-ring on it and held in place with a bracket and bolt and the smaller one is held in place with a spring clip. The dealer gave me a schematic showing only 1 location. The smaller one is located in the channel plate and is held in place with a spring clip. I had no problem locating the larger one with the O-ring. However, I looked all over, top, bottom and both ends and could not locate the smaller one or the channel plate. I know it is in a non-fluild area and the larger one because of the O-ring was located in a fluid area which it was. Now get this. The dealer themselves cannot tell me where the channel plate is located. They had nothing showing the location. Not a single auto mechanic knows or has heard of a channel Plate. These auto mechanics are "GM certified Mr. Goodwrench" mechanics and DON"T know. So gentlemen, can you help me out. Can you help my daughter. Where is it. Thanks gentlemen for your help in advance.

The speed sensor is on the differential cover, passenger side, near the back of the cover. Remove the passenger tire and you should see it. Replace that first. If it'* the input sensor, that'* a bit harder to replace. That'* inside the transmission on the drivers side. You would need to remove the sub frame, then lower the engine/transmission far enough to remove the side cover. This is also where the channel plate is. I will see if I can find a picture.

This is what'* under the side cover on the drivers side. The input speed sensor is plugged in to that harness.

This may come in handy as well.

Thanks Dan for getting back to me so fast. The sensor that I replaced was located on the passenger side on the top of housing that the passenger side drive shaft comes out of going to the wheel. This was the larger of the 2. It has the O-ring and is held down with a bracket and a bolt. So this is the output sensor? I had no problem locating it. So you are saying that the input speed sensor (the smaller one) and channel plate is located INSIDE the trans on the driver'* side and that I would have to drop the engine and trans to replace it. Am I correct on what you are saying. Mike

Ya, it'* a pain but doable. You jack the car up as high as you can and then use 2x4, perhaps 4 or 5 feet long, put them on the unibody and use jack stands to support the car. Support the engine from above, a 4x4 and chain works good. Then remove the sub frame. Make sure you wire the power steering rack to the exhaust manifold so it wont fall down. Make sure everything is disconnected from the sub frame. Then use a jack to lower the drivers side of the transmission. Once low enough, remove the side pan. You will need to drain the transmission oil. Changing the sensor is real easy. Reverse to put everything to put it back together. Give yourself a whole day.

Here'* how to support the engine.

Thank you so much Dan for the pic and the sensor location schematic. My daughter thanks you. I knew it had to be on the drivers side end just didn't know it was in the trans. I know what to do now. Thank you again Dan for your help.

No problem. Just make sure it stays clean.

Dan, I just got the add'l pics and instructions on how to do the job. Thanks again my friend. I will let you know how it all comes out. Thanks again.