I have this 2000 ford ranger. V6 4.0 2wd. Automatic that has the garage it is at stumped. First off, a rebuilt engine was professionally put in about a year ago and has less than 10,000 miles on it. Just had a rebuilt tranny professionally put in about 4 months ago. They were unable to road test it due to its current state which is: It revs out fine in park or neutral but soon as its in a drive gear it shimmys and goes about 2 mph, might make it up to 25mph. It doesn't appear that pushing down more on the gas pedal makes any difference as far as the rpms goes (not 100 percent positive on that, been gone since it was towed from the tranny shop to garage) It does have kind of hard shift into reverse and a little harder when shifting into drive. It does everything it’s supposed except move really, it may make 25mph. I can manually shift it from park to reverse to neutral and so on, hear it shift with a slight clunk noise and it will go forward. The shop it’s at has replaced coil pack, plugs and wires. None of it made a difference. They ruled out the cats, the mass air flow sensor, no leaks on the intake manifolds, fuel pressure is fine all the way around. They consulted with Ford mechanics without success except Ford’s suggestion to have it towed in so their computers can check it out. I would like to avoid that $$$ visit and another tow!!! I can get more details in regards to what is or what isn't working. Any help will be greatly appreciated.