Sounds like a internal transmission failure, look for a good mom and pop transmission shop
When a Mercedes C280 will not move in forward or reverse it is an indication that the transmission is going out or has already gone out in the car. This is true of all cars, not just a Mercedes.
Could be a pump problem or broken planetary. Regardless, the transmission will need to be disassembled.
If your Mercedes ML won't go in reverse, it could be due to several reasons, such as low transmission fluid levels, a malfunctioning transmission solenoid, or a faulty gear shift linkage. Additionally, issues with the brake system or electronic controls could also prevent the vehicle from shifting into reverse. It's advisable to have a professional mechanic diagnose the problem to ensure proper repair.
If your car moves forward when the gear selector is in reverse, it could indicate a serious issue, such as a malfunctioning transmission or a problem with the gear linkage. The reverse gear might not be engaging properly, allowing the car to move forward instead. It's essential to have your vehicle inspected by a qualified mechanic to diagnose and fix the issue, as it can lead to dangerous driving conditions.
Another problem might be the sun gear drive shell in your auto transmission. GM 4L60 transmissions are notorious for this problem causing a no reverse symptom. this means that you will need some serious work done on your vehicle
Could be cable or linkage out of adjustment. Verify from underneath is actually in drive before you do anything else (with a helper)
It could be the transmission, it could be some parts under the vehicle that rub only when travelling forward.
When a Toyota 4Runner will not move in reverse, it could be that the reverse band in the transmission is broken. Another possibility is a problem with a range selector. Both problems would need the services of a transmission expert because the transmission would have to be pulled.
A car that won't move when in reverse could indicate a problem with the transmission. It could also indicate a problem in the gear selector.
If your Mercury outboard motor goes in reverse but not forward, it could be due to a few potential issues. One common cause is a problem with the shift linkage, which may be misaligned or damaged, preventing it from engaging the forward gear properly. Another possibility is that the propeller or lower unit has sustained damage, affecting its ability to transmit power in the forward direction. Lastly, issues with the control mechanism, such as a faulty throttle or gear shifter, could also be at fault.
If the car does this every time, but is ok in forward gears, then the transmission could have an internal problem. There could also be an electronic issue. If possible, run the computer codes for any bad codes to appear.
IF it is a rear wheel drive vehicle it mabe something wrong with the gears in your final drive...