94c4seminole

This anecdote is about my 1994 Corvette LT1 with 4L60E automatic transmission. Instructions for how I replaced the Vehicle Speed Sensor (VSS) are included below because I had not found them online. I used the Service Manual for reference.

I have been looking for the source of a vibration which I thought may be coming from the transmission. A shop owner advised me to try engaging the transmission with the drive shaft off the car to see if the noise/vibration still occurred.

When I did this I heard a new, high pitched clicking noise, so I turned off the car and put it back together.

When driving it after that, I noticed the speedometer was fluctuating even when I was at a constant speed. It became most noticeable around 40-50 mph, and when I tried to get on the highway the transmission started shifting back and forth between 3rd and 4th and eventually went into "save myself mode" and started shifting hard in the lower gears.

The output shaft in the tail housing of the transmission has play when the drive shaft yoke is not slipped in around it, so I believe it had the freedom to bang around in there, causing damage to the Vehicle Speed Sensor (picture). The metal probe was bent and pushed back some as I suspected, and once I replaced it there was no longer a shifting/speedometer issue.



Instructions: The sensor was cheap, quick, and simple to replace. I jacked up the driver's side of the car and placed two jack stands, one at the front and rear of the driver's side. The sensor is located on the driver's side of the tail housing. There is a two pin plug that goes into the sensor and one bolt that holds it in place. I used a 10mm socket with universal joint and a medium sized extension. Once the bolt was off, I used a flathead screwdriver to gently pry the sensor out.
(You may lose some transmission fluid at this point so make sure to have some around. For me the car was not hot, and was tilted so that I lost an insignificant amount of fluid.)
I cleaned the orifice with a shop rag, wet the o-ring on the new sensor with a small amount of transmission fluid, and lined it up so the bolt could be hand threaded in. Then I pressed it in until the O-ring snapped into the groove. Next I tightened down the bolt gently until it was snug (11 N-m if you can get a torque wrench down there).

It took me a while to research this and figure it out, so I hope this helps somebody like me who has less knowledge of these things.

I wonder if putting the car in gear without the drive shaft on was good advice or not. I have heard two mechanics say it is a usual test to do, so I don't know what to think.

Update: I removed the new sensor due to ongoing chirping noise that was the speed of the drive shaft. I filed down the probes some and resolved the issue. More detail in post #8.

The Green Hornet

Thanks for the write up, where did you purchase the speed sensor?, I need to replace mine as it is acting up.

confab

Exactly. I don't know why he suggested this, but it's not a diagnostic aide.

94c4seminole

I bought a Carquest by BWD sensor from Advance Auto Parts for $34.99. It initially made some slight chirping sounds, but I haven't noticed it as much the last couple of days. I think it must just barely be touching the cogwheel at times, which may be an indication that my output shaft bearing is bad.
The sensor has been great. The transmission shifts very smoothly now. I think the sensor had been slightly damaged before because I don't remember it ever being this good.

94c4seminole

I kind of figured that after the fact.. I do wonder if it means my output shaft bearing is bad, which may have allowed it to have even more play with the yoke out of it. I am going to be replacing my motor mounts as soon as I get them. We will see what fixes the vibration in the end.

confab

I doubt it's a problem. It's a bushing in the rear of the case on the 4L60E, and by the time it fails you'll need a trans anyway.

The tail shaft housing bushing and yolk help keep it all straight. If you see any wear there, it's not difficult to inspect/replace that one if you think the yolk is too loose.

confab

Probably just poor QC. You can carefully file on those a little, BTW.

It's not particularly picky.

94c4seminole

The chirping noise continued, so tonight I took out the sensor. It was clear where the contact had been occurring, but it wasn't enough to cause malfunction. I alternated using a metal file and some sand paper to smooth down the metal probes until they were raised just slightly above the level of the plastic housing. I rounded down the sharp corners of the probes as well.

Took it for a test drive and had no more chirping and shifting is just fine! Thanks for the advice.