Inside the aluminium top cover of the gearbox, which is secured by two large Phillips head screws, you will find two large springs which rest on a L shape steel plate which give your 3rd/4th bias gate position. This L shaped plate is very prone to cracking off where it is bent which will result in you losing the 3rd/4th rest position when in neutral and thus the shifts will become vague. This plate is inexpensive and can be changed with gearbox in situ.The part number of this Bias plate is FRC9340.

When you let go of the gearstick on either the LT77 or the R 380 Discovery boxes the stick will spring to the 3 / 4th gate. This gate position is set by the position of the plate shown here. This gate position must be adjusted correctly to agree with the selectors in the gearbox to ensure a good gearshift. When we rebuild the boxes we set this position but sometimes it needs fine tuning when in the car.

If the shifts to 3rd and 4th are not clean you may want to adjust this plate, to do this first you must drive the vehicle but when shifting into 3 and 4 instead of letting the gearstick go where it wants to go try holding it a little to the left then a little to the right, one way or the other it will drop in nicer. When you have worked this out you can slacken the 4 screws holding the plate and move the plate left or right accordingly to improve the shifts.

The best way of ascertaining the degree of wear is to chock the two front wheels, handbrake off, mainbox in first and jack up a rear wheel. Remove the PTO cover to the left of the handbrake and you will be able to see the gearbox mainshaft in the centre and the transfer case input gear around it. By rocking the handbrake drum you will be able to rock the gear around the shaft thus getting some idea of wear / backlash between the two.

A common fault on the early R380 gearboxes was the 4th gear baulk ring. The slot locating the synchro slipper wears and allows the baulk ring to rotate too far. This blocks the synchro assembly. It will be necessary to rebuild the gearbox, and replacing the baulk ring with a later type will eliminate this fault.

The most common cause is worn mainshaft spline but other things to check the A frame ball joint and the halfshaft drive flanges, especially if you have a 300 tdi Defender. To check mainshaft spline wear remove the PTO cover and with the main box in first gear rock the car backwards and forwards whilst looking into the end of the input gear. If the spline is worn you will see movement of the shaft in relation to the gear. Replace the gearbox and transfer box input gear (use a cross drilled gear to prevent recurrence of the problem).

There are three possible problems. 1) The mainshaft spline has worn away and is not engaging in the transfer case input gear, (most common) 2) the centre has torn out the clutch friction plate or 3) the mainshaft has sheared just inside the rear of the gearbox. 1) and 3) will require a rebuilt unit.

The layshaft extension has sheared off effectively disconnecting these two gears. You require a rebuilt or new gearbox.

Most rebuilt gearboxes, including ours, come without the "turret". This the part that the gearstick bolts to. If you pull back the rubber boot on the turret you will reveal two large springs and two adjuster screws and locknuts. The role of these springs and screws is to set the rest position of the gearstick when you let go of it and is referred to as the 3/4 bias setting. When you fit a new gearbox this can sometimes need adjusting to agree with the selector shafts to ensure a clean gearshift. Firstly you need to work out which way to adjust it, to do this drive the vehicle but when shifting into 3 and 4 in stead of letting the gearstick go where it wants to go try holding it a little to the left then a little to the right, one way or the other it will drop in nicer. When you have worked this out you can adjust the screws the springs are resting on to lean the stick left or right until it shifts better.

A common fault with these boxes is a thrust washer in the 1 - 2 synchro assembly splitting in half and blocking movement. Rebuild the gearbox and replace both thrust washers in the 1 - 2 assembly.

We recommend MTF94 in your R380 box.

We recommend ATF Dextron 2 or 3.

This is very common on both the 200 and the 300 TDi engined vehicles. The clutch friction plate has a ring of springs, which are there to soften the knock of the diesel engine to stop it being transmitted to the driveline. Often especially with a new clutch these springs are quite tight and a lot of the engine knock goes through to the gearbox and makes the gears "chatter" together when the box is in neutral and the clutch up, it goes when the clutch is depressed. This can sound quite bad and does vary from car to car but is not detrimental to the life of the gearbox and we view it as an undesirable characteristic of the LT 77 and R 380 as opposed to a fault with either the gearbox or the clutch.