I have a 2000 4.7 with the 45RFE gear box. The problem I have is that when cruising above 60mph or above in Overdrive, the Revs keep going up and down by about 200rpm. I was told that it could either be the Lock-up clutch on its way out or a faulty speed sensor.

I recently changed the torque converter for a higher-stall unit but it was doing it before the change with the old one. I think this rules out the lock-up clutch, as its is inside the TC, if I understand correctly!

There haven't been any CEL's or codes thrown up.

Can anyone tell me where on the gearbox the speed sensor is and is there any way to check them? I assume it would be the one on the box and NOT the one on the axle?

Thanks in advance!

 

Yes it sounds like it is a bad speed sensor or a faulty TCC solenoid. Or wires to either one.
Here is a copy and paste from the service manual.

DESCRIPTION
The Input and Output Speed Sensors are two-wire
magnetic pickup devices that generate AC signals as
rotation occurs. They are mounted in the left side of
the transmission case and are considered primary
inputs to the Transmission Control Module (TCM).
OPERATION
The Input Speed Sensor provides information on
how fast the input shaft is rotating. As the teeth of
the input clutch hub pass by the sensor coil, an AC
voltage is generated and sent to the TCM. The TCM
interprets this information as input shaft rpm.
The Output Speed Sensor generates an AC signal
in a similar fashion, though its coil is excited by rotation
of the rear planetary carrier lugs. The TCM
interprets this information as output shaft rpm.
The TCM compares the input and output speed
signals to determine the following:
² Transmission gear ratio
² Speed ratio error detection
² CVI calculation
The TCM also compares the input speed signal and
the engine speed signal to determine the following:
² Torque converter clutch slippage
² Torque converter element speed ratio

 

Thanks for such a comprehensive reply. Looks like I'll be under the truck at the weekend!

Apart from obvious damage to the wires, is there any way to actually test the speed-sensors? Also, is the TCC solenoid inside the box or is it accessible without having to drop the box?

Thanks again.

 

Your welcome. The service manual will have a way to test the sensor. You can download it in the stickies in this section.

 

I got two new speed sensors fitted at the weekend and the good news is that it cured the problem. The bad news is that it returned after about 200 miles!

At least it narrows it down to the cause. It must be in the wiring going from the sensors. And as the gearbox end was the one that got touched, it sould be pretty easy to find the bad connection in the connector blocks.

Thanks for the help.

 

how do you find the stickies i am new and computer stupid thanks strick60

 

sounds to me like the typical tps(throttle position sensor) problem. super cheap and easy to fix. you should be good to go in minutes.

 

Look a few posts above this one for one that says FAQ.

 

will the speed sensors effect the transmission shifting? occassionally it will not shift to overdrive. I have to turn the engine off and restart it to shift. Also, my torque converter senor is malfunctioning, do I have to change the torque converter? Thanks in advance

 

Hey, did you get the problem fixed. My 2003 does the same thing. Above 55 or 60 mph cruising, the overdrive will unlock for a few seconds...then lock back up (rpm goes up about 400, then back down). It does it about once every minute...but does not do it all the time.