1993 Chevy G20 5.7LSpeedometer needle would occasionally not work while driving. Also the speed sensor in the driver's side of the transmission was leaking fluid, likely from the old o-ring, so I decided to replace it. After installing the new speed sensor the speedometer needle would act erratic going all the way up to 70 down to zero and fluctuate anywhere in between. I ended up putting the old speed sensor back in.
Was there anything I should have done differently? Any tips or advice or appreciated.

 

if the sensor is grounded through the case, make sure the threads are clean and don't use pipe seal tape.
The depth probably has to be set correctly.
Make sure the reluctor ring is in good shape, clean and free of metal shavings.

 

the new sensor was tough to seat due to the o-ring. It's possible it didn't allow a good ground.

 

These things have a flange as to set the probe length as what it should be. If the O ring kept it from seating properly, it would be too far away from the recluctor ring, and cause this issue

 

thanks I will give it another try. It certainly didn't seat flush. It was quite stubborn trying to get it in compared to the old one.