2001 4r100 fresh rebuild , no 2nd to 3rd shift ( just replaced shift valve), about to order solenoid pack, here to make sure this is a PWM solenoid pack that i need, not a NON PWM. have a new OSS and VSS installed , ordered ISS. When unplugged it does go into 4th gear safe mode. im believeing it is electrical, thanks, for everyones help, ROnjon

 

Yes. An '01 4R100 has the Pulse Width Modulated Torque Converter Lock Up.

 

ok thanks, i didnt mention this has a pto , not sure if that affects the dynamics

 

Makes no difference.