I first noticed the RPMs surging by 200-500, eratically, just driving down the highway. Then the 'service engine soon' light came on and the overdrive light blinks consistently, though not constant. I ckecked the DTCs and it listed P720, P721, P722, P1000 and now a new one P1270-which I believe happened b/c its not shifting@ the usual RPM. Could all this be do to the output speed sensor?
How can I check the Output speed sensors? I made sure they were connected.

 

I don't know what the codes mean and don't know much about the speed sensor, but from your description it sounds like the torque converter was locking and unlocking within the same gear. Maybe the torque converter lockup clutch is going?

 

Whoa! on edit I spoke to soon , its late and this is not the vss sensor problem.
let us dig a little further into it.
Rich





Replace your VSS (vehicle speed sensor) mounted on top of the rear diff.
clean the dirt away from it before removing.
I'll chk the codes in the morning and give you an explanation of them.

Rich

 

P0720 Output Speed Sensor Circuit Malfunction
P0721 Output Speed Sensor Range/Performance
P0722 Output Speed Sensor No Signal
P1000 Transmission Solenoid Malfunction - OBD II Test Incomplete
P1270 Vehicle Speed Limiter Reached

 

Okay the tss sensor and the oss sensor are located on your transmission .
You may have a harness problem!

You can chk the sensors by resistance
Tss should be within 496-1,244 ohms across the pins(for pto aplications)
781 -1,979 ohms for non pto appl.
Oss sensor should be 781-1,979 ohms

Rich

 

Appreciate the help, I'll get on on it tomorrow!!