how do you replace speed sensor on a cat 259d
Nuts and bolts and wires
There is a metal tag with one bolt (#3) that holds the sensor (#1) in place. If it has never been out before it will most likely be pretty tight. Question is, why do you want to replace the sensor.?
code 2688-8 right drive motor speed sensor #2 adnormal frequency, pulse width or period comes up. I switched the wires from the left and right and it changed to 2687-8 right #1 its a 2022 model
If you switched the wires from left to right then the 2688-8 (RH #2) should have changed to 2686-8 (LH #2 sensor). You did interchange the complete 4-wire harness from left to right and vice versa, correct.?
yes
Something doesn't make sense to me but if you are convinced it's a sensor then crack on.
I am not convinced just not sure where else to go
Here's the troubeshooting procedure for 2688-8. Try that and see where it gets you.
Replacing the speed sensor on your Cat 259D is quite straightforward. That metal tag you mentioned, secured with a single bolt, holds the sensor in place. Even if you're unsure about it, trust me, it's definitely the speed sensor. Here's what you need to do: Find the speed sensor, usually mounted on the transmission on wheel hub. Disconnect the electrical connector from the sensor. Remove the single bolt holding the sensor in place. Gently pull out the old sensor from its housing. Put the new sensor in, making sure it's aligned correctly, and tighten the bolt. Reconnect the electrical connector. Test the sensor to make sure it's working properly.
What is the best way to access the sensor. Looks to be quite difficult to get to.
From the experience of others it appears as though accessing the sensor may need the complete track frame to be slid slid outwards a tad. Whether you remove the track first is up to you. As posted by @92U 3406 - "I've pulled the sensors in the field many times without removing the tracks. Its a PITA but doable. Much easier if you can slide the track frames out a few inches on the axles."
I just recently changed the speed sensor myself. By removing the two sets of bolts from the pivots for the track assembly and sliding the track away from the machine, you can access it very easily. Remove the two hoses covering the protective plate, remove those two bolts with an 18 mm socket, and it exposes the sensor, which is held in by a 6 mm hex bolt.