Hello. So I have a 95 f150 with 4r70w. I recently replaced the sensor in the rear and the transmission. Since I've done that the speedometer is bouncing bad never had before. Hard shift from 1-2 is gone. So I put the Old one back in the transmission same. I have to see if I can find the old one on the back diff. What one actually controls the Speedo?

 

I believe the speedo runs off the one in the trans and the abs runs off the one in the diff

 

Rear axle VSS is used for the Rear Anti-Lock Brakes (RABS) and the speedometer/odometer like all 1992 and later trucks.

OSS transmission sensor is used for transmission control by the computer (PCM).

 

Not all
The 4x4s still have a VSS in the transfer case (up to 97 at least)
The input and output shaft sensors in the trans (like rla2005 said), are just for the trans
Check the plug (connector on that rear axle sensor if a 4x2) for your problem
Check for hair on that magnetic rear axle sensor (excess metal filings)

 

While you're there, If you have an altered exhaust, check for melted wires in the area of the rear axle.