Speedometer stopped. Odometer still goes.

My sister has a 1991 Volvo 740 GL 4 cylinder 4 speed automatic rear wheel drive cant remember if it has ABS or not. Her spedometer has stopped working but the odemeter still keeps mileage and the cruise control still works and maintains speed but its anyones guess how fast shes going. She was in an accident and the passenger side rear wheel was struck and knocked out of round and warped the brake drum, rim, and wheel hub so all that was replaced. She thinks its a wire or sensor in the rear and I cannot find it if thats it. But it doesnt make sense to me to think its a sensor when the mileage is still going. I have resoldered all the connections in the dash so what else could it be? I know Volvo is bad for electric problems but all are easy fix. This is just a mystery to me. Any and all help is appreciated. Thanks! =)