Ok here's what I've got going on. I've got a 92, V8, automatic trans. My speedometer died a couple of months ago. So I put a new VSS on the transmission... still nothing. I pulled the buffer box to check for any obvious issues but I haven't found any.


The thing is, I can't find a replacement buffer for the car. Unlike most cars my box was a white color and the model number is: 25007342-D I'm not sure if the buffer has been replaced at some point with a "close enough" model or what. So if anyone knows where I can buy one, I'd appreciate it.


But just assuming that my hunch is correct and the buffer box is fine, what else could it be? I checked the pcb on the speedometer and it seemed fine. Maybe a wiring issue? What can I try to narrow it down?

 

Just thinking out loud here and throwing out suggestions for discussion so forgive me if my logic is flawed.

Does your cruise control work?

If it does, I would say the problem is the speedometer. I say this because the cruise control has to get a road speed reading from someplace. If the cruise control works, I would assume there's nothing wrong with the VSS circuit and the problem is the speedometer itself.

If your cruise doesn't work (it won't work for reasons other than no road speed signal) or your car doesn't have cruise control, borrow a scan tool. A scan tool should be able to read road speed. If the scan tool is reading road speed then you can assume the electrical circuit is good from the VSS to the ECM.

I believe the the cruise control and ECM get road speed after the buffer so this would eliminate the buffer as a culprit.

Also, have you noticed or can you even tell if the torque converter lock-up is acting weird?

 

Cruise doesn't work. Actually I can drive the car with the VSS buffer removed and it behaves exactly the same. So that's wiring or the buffer itself. I still can't track this one down anywhere. You'd think as common as these were on early 90's GM stuff I'd be able to find this particular model somewhere.