Question: have a 2001 ford explore it will not go back in reverse there was a bang that came from the rear before it happened at times it will go into gear but the problem i know is in the transmission
Answer: You most likely have a 5R55E Ford transmission which was the first 5-speed automatic transmission to be employed by an American automaker. The 5R55E featured more accurate computer controls (to accommodate the additional forward gear) and introduced adaptive shift control.
In this case I would agree that you have a transmission problem. If I were to guess, and this is a guess, because as I have discussed in the past, it is impossible to diagnose a transmission over the phone or Internet.
Without being over detailed, more than likely the reverse band has broken or the reverse servo is damaged. I say this since you heard a “bang”.
It would be wise to take the vehicle to reputable transmission shop for diagnosis. By lowering the transmission pan for an inspection by a trained specialist one can determine if the servo is broken. The servo is the hydraulic apply mechanism and can be replaced in the vehicle. BYW, if you have luck on your side, have the filter changed and insist in synthetic automatic transmission fluid.
Chances are that your reverse band broke, which would require transmission removal and dis-assembly. In a few isolated cases the band can be changed and the transmission resealed and put back in your van. Generally speaking, in most cases the transmission is worn throughout the entire unit and the band was the first thing to go bad.
If you decide on a rebuilt transmission, the better supply companies put an upgrade kit in the valve body of the transmission, which in essence is the brain. This upgrade kit specifically addresses the pressure control issues that causes the broken band, along with a slew of other issues as well.
With that being said my suggestion would be to call the gentlemen at GotTransmissions.com (866-320-1182) and discuss with them your alternatives. My 30 plus years in the transmission business has exposed me to every possible transmission company in the USA, it seems. The one company that has always stood alone from the rest is GotTransmissions.com. They are committed to providing the most up to date transmissions and good used transmissions with low mileage.
What ever is diagnosed as your problem, remember that nothing can replace the value in purchasing a reliable product from a well established company. Although GotTransmissions.com is the most affordable company I have ever done business with, it is not the price that really draws me to them, it is the quality, and that is the most important paradigm. Buy a top quality product and pay for it once.