Replacing vss(vehicle speed sensor)

A friend has a '92 Roadmaster and told me yesterday that his speedometer is going haywire. I believe he has an electric system that eliminates the old speedometer cable. On older cars I have replaced the gear assembly in the side of the transmission where the cable would attach and solved the problem. I'm wondering if anybody has replaced the vss(vehicle speed sensor) on a newer car?
According to the shop manual it looks like this replaced the mechanical gear/cable assembly. There is also a vehicle control module in this circuit. Do these often go bad?
The sensor looks like it's bolted to the side/rear of trans. but shop manual shows a special puller to remove. Is this necessary? Or can it just be pulled out?
Any tips would be greatly appreciated. Thanks, Formzy

The VSS is nothing but a small AC pluse generator that feeds the PCM pluse information that it inturpets into speed. It just pulls out of the transmission tail housing just like the old gear unit.

Thanks for the reply. The more I study it and look at the problem I think the problem still exists with the gear rather than the vss. I believe their plastic and the teeth get broken off and or worn down causing eratic speedometer behavior. I'm going to try to get the right one(4 types exist) through the last 8 digits of the v.i.n.

I replaced one on a '85 Pont. GP 15 years ago and the only difference was that had the old speedometer cable set-up, but the gear is what regulates the speed info now through the vss and back to the cluster. Has anybody changed one recently?
Thanks

My Speedo stopped working and I too replaced the VSS only to find that the gear on the shaft itself slid forward and wasn't turning the VSS gear.
What made it slide is anyone's guess, however a screw driver carefully placed on the gear (careful because it's only plastic) was I able to slide it back into position (tight fit also). Been working fine ever since. Hope this helps.

Does anyone know why my trip goes backwards on the expressway? It is fine in town, but seems when I get on the gas it stops turnning until, I get to speed and let off then it starts to count backwards. 92 estate