I have a massey 399 M reg done about 6000 hours. Its got the 18 speedshift gearbox. I was driving along In top gear and it lost drive. I stopped and made sure the rang hadn't jumped out. I can only get it to move In Medium box. The gear stick feels fine and it feels like the ranges are being selected and the lights change. In hi it grates a bit like its not quite in gear and in low it just doesn't move. I know the range change springs do play up but from what I have been told the symptoms don't match! Any ideas? Thanks Matt

drive shaft popped out or the clutch has gone. might still look attached but it will be disconnected in the dif. push it back in. or remove completely and replace the circlip as this is the only thing that hold the drive shaft in place. driving to fast around corners can pop the drive shaft out. can also lose all the gearbox oil if the seal is broken.

Cjeck fluid level under red lid on top of gearbox if this is correct the black switch on top of the gearbox large has about 6-10 wires connected

Can you tell me are you changing gear at the time or are you driving in the same gear when it occurs?

Chsnge the alternator, anything that blows a 100 amp fuse is a definate direct short to ground. Check for a loose or broken connection

You have a faulty ECU which will need replacement. You may have damage to your gearbox now as a result.

Sounds like a clutch problem to me.
So, with the engine off, can you select all gears? If yes, your gearbox is probably OK.
And now with the engine idling, can you select any gears with out crunching? If this is difficult, then try this next test in an area where movement forward or backwards won't be a problem.
With the engine OFF, foot ON the clutch, the handbrake OFF, and in 1st gear, start the car. BE READY TO TURN IT OFF.
If the car moved forward as you cranked the engine, then your clutch is not adjusted properly or has worn out. That is more-than-likely the smell you got before - burnt clutch disc from it slipping.
You can drive it, but every time you want to start off, you'll have to turn the engine off, select 1st then start the engine. Accelerate slowly, making sure the revs don't rise faster that you're speeding up, and change gear by judging engine revs between gears.
Don't keep driving it as it is, as you WILL have gearbox problems if you don't fix the clutch.

need to check speedo sensor or drive gear in gearbox is connected,may have been disconnected after work was done,or the sensor has packed up,unlikley to be speedo itself if its been ok in the past

the front drive axle on one side may have not been installed all the way in to the transmission, check to see if it is loose and have some one look under front end with engine on, front end jacked up, emergency brake on and in gear to see if a axle is turning. if one is and yhe other is not put the car in park and turn\ roll the wheel that was not turning by hand if it rolls your problem is most likley to be the axle has come loose from the transmission

mercedes E320 stays in drive mode and dosent change gear