Chevrolet Repair: 94 s10 blazer speed/odometer probs, blazer s10, s10 blazer

Question
hey there, this is one I've never seen before....

I have a 1994 Chevy Blazer S10 4x4 with over 170,000 miles on it. A few days ago, my ABS light started comming on. When it did, I had several problems start at the same time.... both the speedometer and odometer stopped working, and the truck would no longer shift gears when in drive/overdrive. I took it to a repair shop to run a diagnostic. they said their best guess after looking at the codes is the speed sensor in the transmission or the buffer that feeds into the computer from the same sensor. I spent the money for the sensor only to find it didn't help anything....should i try to replace this buffer he was talking about, or is there something i should try first... I have the codes if they will help you with this one.

don't worry, I will be taking the sensor back to get my money back.....

thanks in advance for your help....

Answer
Hi Chris,
What they said is a good guess.
If they had a scan tool connected, though, they should have been able to get a speed sensor reading, unless there is a bad connection in the wireing harness somewhere.
The buffer should have no effect on the ABS. I believe the ABS gets its signal from the speed sensor before the buffer. So I would check those connections first.
Another thing to check...Where the speed sensor goes into the transfer case. Jack a rear wheel up so you can turn the driveshaft. Have the speed sensor out, and look in the hole at the shaft. There is a magnet, actually looks like several teeth. They must rotate with the shaft. That is the thing that gives the sensor a signal.
Good luck returning the new one. Usually, once you leave the parts house with an electronic part, you own it.
Van