sorry didnt see this but the motor can be sticking on the start up test and thats why it comes and goes i engage my 4WD motor on my truck atleast 2 times a month to keep the motor moving so it dont build up corrotion on the brushes
im here to help but you all have suggested what i whould have good job all. i was checking all data and they say it could have the 6 speed also in it they did have a drum issue that could give this problem.can you get us what transmission it has
ok what you are feeling is converter shudder comes in about 45 mph . There is a product i highly recommend its called SHUDDER FIX my Dr Tranny most parts stores stock it buy 2 tubes and add to your trans in about 300 miles you should see a difference i use this at my shop on all transmission...
they still have that problem on this unit and the 42RLE transmission i have seen planet but you normaly find metal chunks in the pan. i have seen a stripped input planet do this also i replace the planet set on every rebuild i do at my shop