99 gmc jimmy transmission slipping no reverse, will transmission flush repair the problem

Hi check the colour of your transmission fliud is it should a medium red if it looks dirty brown or any other colour that would suggust your clutchs are slipping if your transmission fluid is low or over filled it will cause your problem you can drain your fluid remove your lower sump pan clean the boxes main body and filter replace the oil and try there is no gaurentee it will work but this is a basic you can do and these type of repair can resolve your problem if the fliud is brown then this and an adjustment of of the boxes clutchs and bands must be done this can be done with the transmission in sitution there are other things that can cause the problem but these are well worth doing first as it will not cost a fortune and has a good chance of success yates210456

I am havin the exact problem and gc dont even seem to care at all I have always had a gmc but i will never get another one