Mine does the pulsing first thing in the morning after going a few feet. It never did that before so something is wrong or is going to be wrong soon if we don't find the problem.

My guess is its the rear sensor. With the diff weeping and all the debris that goes past there it wouldn't suprise me if the thing is on its way out. If it threw a light I could check the code using my make shift code reader but it doesn't. It does it for about a couple of seconds sometimes accompanied by a springing sound (boooiiiiiiiiinnnng) and its done for the day.