We’ve recently started selling Ashcroft Transmissions’ reconditioned gearboxes.  The wealth of knowledge those guys have picked up over the years is amazing.

Over the next few days we’ll be adding some of their most frequently asked questions to our Blog.  First, we start with the LT77 Gearbox……

My 200 tdi Discovery is very difficult to change gear from 1st to 2nd or 3rd to 2nd. Why?

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.

What oil should I use in my LT77 gearbox?

We recommend ATF Dextron 2 or 3.

My gearbox rattles on idle, in neutral, with the clutch up

This is very common on Diesel 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.

I’ve just fitted a rebuilt gearbox to my Disco/Defender, the third and fourth shifts are not very good. Why?

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 bias plate. 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.

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.

I’ve just fitted a rebuilt gearbox to my defender, the third and fourth shifts are not very good. Why?

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.

When driving my 200 Tdi Discovery / Range Rover the gearstick has suddenly become very vague and is flapping side to side. Why?

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.

The above frequently asked questions are courtesy of Ashcroft Transmissions.