P2161 where is the sensor, what repairs are needed , changing gears auto transmission.

Question

When driving my chev, as it approaches hiway speed, it will sometimes chug , like it was trying to gear down , when it shouldn't have, the engine light comes on and a warning light alarms.
When the truck is turned off and restarted the warning light goes away the code is P2161 says
Vehicle speed sensor B Intermittent/erratic/high, ABS temporarily shut off.
We had no choice but to continue as we were far up north with no help nearby , the same thing happened a few more times, when driving on a flat stretch would seem to try and pick a lower gear, for 1/2 a second then revert back into the proper gear. it is an auto transmission,
I was wondering , where is the speed sensor B ?, what does it look like? how hard is it to change?

Answer 1

the speed sensor 2 will be on the transfer case

see picture below