69SSC5

1989 corvette,,, 700r4 transmission.
gears were changed years back and spedo hasnt worked since.
I replace the VSS sensor with a new sensor, i put back on the 34T gear that i took out. result = spedo and odo still didnt work. took the vss sensor back out rotated it 180* and put it back in. result = spedo and odo still didint work. took the vss back out put on a 44T driven gear and put the sensor back in at the 180* rotated position... result = spedo and odo now work but are 5% off (no big deal, i can live with that). 12 miles later driving along and suddenly the spedo and odo stop working. i go home put the car in the air, pull out the VSS (the gear stayed in the trans when i pulled it out). i put a drill on the VSS spun it up and the dash showed MPH (like i was speeding). So the VSS works, the VSS wiring is good. So what happend? did the driven gear come off of the VSS? The drive gear in the transmission and the driven gear on the VSS both look like new. no unusual wear or tear.

Sparkytfl

Was the drive gear changed when you did the rear? Was it mounted with the clip in the right hole? The drive gear should be pretty much centered front/back when you take the sensor out and look in the hole. I'd check that, also feel the drive gear and make sure it's still firmly attached to the output shaft and not loose, and make sure that the hole in the driven gear still has it's "D" shape and isnt rounded out.

69SSC5

Not sure what was done when the rear end was changed. I got the car long after the rear was swapped. With that being said it does appear thar the drive gear was changed to what looks like a smaller drive gear. The drive gear is not centered in the hole it is posituoned on the shaft with a bias tword the front of the hole. The drive gear is firmly cliped onto the shaft and does not appear to freespin

69SSC5

Driven gear is in like new condition and the hole is not rounded out.

Cliff Harris

There are two mounting positions for the drive gear on the trans output shaft. The gear is held by a small clip that locks it into one of two holes. The holes are about 3/4" apart. The drive gear should be centered in relation to the VSS hole centerline. It should be pretty obvious if the gear is in the wrong hole. I suppose it's possible that the clip is missing completely. My gear was a very tight fit, so it probably wouldn't move once it was put in position, even if the clip was missing.

Also there are two VSS senders. One offsets the driven gear farther away from the drive gear to allow for a driven gear with more teeth (larger diameter). My parts book shows:

25007224 (Delco 213-210) vehicle speed sensor (with D9A)
25007308 (Delco 213-223) vehicle speed sensor (with D9B)

I don't know the difference. I looked at my trans since it's out of the car but I didn't see a part number or any other markings on the VSS.

I found this chart in my parts book (700r4 is the MD8 option -- my car with a 3.07 rear has the red drive gear and a green driven gear):