Well, here's the latest. I pulled out my multimeter and tested both sensors. The sensor at the differential tested fine, the one at the transmission tested bad. I went ahead and replaced both of them anyway. The new sensor in the transmission doesn't have the proper 20 tooth gear yet, all I had on hand was an 18 tooth gear so I used that to test it out. I also added 4 ounces of mercon to the parking brake assembly just for fun. I fired it up and drove it around the block a couple times. At first it was shifting rough, but as the engine warmed up it was shifting fine at about 10 mph and then at about 20 mph. I parked it, shut it off and then remembered I wanted to park it on a hill to see if would slide, so I fired it up and drove off again - this time it wouldn't shift at all. I drove it around the block twice more and it wouldn't shift.
I parked it and pulled out the transmission sensor, it looks fine, has some ATF on it, but it's not hot and the gears look perfect.
One thing I noticed last weekend was that I could feel pieces of the old melted gear in the parking brake assembly through the fill hole - I thought that if it shifted fine I would take it in and have the parking brake assembly taken apart and flushed out. Perhaps this has something to do with it?
The other thing is that I had to test with an 18 tooth gear, not 20 tooth. Is this an issue?
What do you all think? I also went ahead and checked all the fuses, they are all fine. I hooked up two code readers and neither showed any codes. I also disconnected the battery and let it set overnight this weekend just to be sure everything was reset and good to go.
