Blazer 99 box problem

Good brothers! , I have a Blazer 99 4x4 automatic, the box does not slide!, grabs drive perfect!, just as neutral and setback! But what are 3rd 2nd and 1st, does not grab them, if you go on a descent and put any of those speeds, and not grab, what could it be?

If the box is electronic, it is most likely that it is some electrical component that does not anticipate its function, now they can be small precion valves that are inside or the dirty filter, anyway you have to disassemble the box and I do not recommend that you get it since you necita a lot of experience to disassemble one of these, since they are very complicated, take it to a workshop and save the bad time.

I consider that for that there are the manuals not .. ?? ... for that we share manuals and solutions, so that everyone who wants can do it in their own way. Or that such manuals are not made by professionals .. ??

Hello, I had a blazer with the same problem solving the winding of the sensor valve, and ready, in the concessionary they said that they had to disarm the entire box but it is not so.

What is that sensor valve?