Series Land Rover Gearbox Rebuild


This page is here for the benefit of other Series Land Rover owners who find themselves, for whatever reason, needing to rebuild their gearboxes. It's not intended to be an exhaustive set of step-by-step instructions for the rebuild. Rather, it's supposed to be a list of those things the workshop manual doesn't tell you. I had to discover them the hard way, and I'd like to think that someone else can benefit from all the grazed knuckles, broken tools and futile hours of labour I suffered through. Of course, your Land Rover will be different. They all are, but then you probably knew that already.

In this text you'll see sections in boxes like this. They're intended to be handy hints. If you read nothing else on this page, read them. They will save you the most aggravation. Use them in conjunction with the workshop manual and your life will be a lot easier.

Background and The Fault

Our story starts one hot June afternoon in Mansfield. Waiting at some traffic lights, engine idling, gearbox in neutral, a new noise presented itself. A sound rather like someone rattling marbles in a bag. Now, every Series Land Rover driver develops a finely-tuned ear for the most subtle variation in the symphony of sounds produced by the vehicle, knowing each squeak and rattle intimately. A new noise could mean anything. Is it just something loose in the dashboard? Perhaps it's hot oil bubbling gently from a mildly blocked breather? Or, heaven forbid, is it a sign of some impending mechanical disaster? There's only one way to find out: keep driving.

And so onwards we drove, thundering down the A1 with no apparent ill effects. Until, arriving back in Cambridge, I tried to accelerate in third gear. Accelerate, of course, being a term I employ in its loosest sense. The surge of power from the asthmatic engine clearly upset something in the gearbox. The gearlever shook violently, then settled down. It's never done that before. But could I make it do it again? Of course not.

The weeks and miles passed by. The strange marbles noise was still present, and occasionally the gearlever would try to shake itself out of my hand, especially in third gear but occasionally in second too. There seemed to be no particular pattern to when it did it: just whenever it felt like it.

First steps

Eventually I found myself with time to investigate what was going on. I removed the floor and transmission tunnel, and then followed the instructions in the workshop manual for removing the top of the gearbox. The operation was straightforward enough, and before long I could see inside it. A careful inspection revealed a missing spring in the 3rd/4th gear synchromesh hub. Aha! I thought. I've read that those are renowned for going missing. That must be the problem: one missing spring, out of three, would put the hub off-centre, making the whole shaft vibrate and, via the selector fork, the gear lever.

Don't try to run the engine with the top off the gearbox. Although it seems like it would be a simple way to see what's going on, all that actually happens is that the first and second gears pump the gearbox oil all over you in a spectacular but smelly and messy fountain.

To confirm my theory, I drained the oil from the gearbox to see what debris was down there. There was lots, as you will see from the following picture.

mangled spring

On the left, a nice new synchro spring. On the right, the pile of junk I strained out of the oil. It seemed to me that there was slightly too much debris, and it was slightly too thick, to be a single spring, but perhaps they'd changed the design over the years. Yeah right.

A quick trip to my local Land Rover dealer got me three new springs for the princely sum of 48p each. I felt quite smug: it had looked like this was going to be a complex repair, and now it looked both simple and cheap. How wrong I was. It was while trying to fit the new spring that I decided it was worth documenting this for the benefit of other Land Rover owners.

Replacing a Synchro Spring

I'd read in various places that replacing synchro springs in situ was supposed to be tricky but possible. However, noone actually seemed to have written down how to do it, which I found mildly suspicious. However, armed with various pliers, tweezers, forceps and other instruments of torture I set to. How hard can it be to slide a spring into a space it was designed specifically to fit?

To cut a long and frustrating story short, I could not find a way of fitting the new spring. It wouldn't slide in from the back of the gearbox and it wouldn't slide in from the front. I could get it so far and then be unable to wiggle it any further. I tried sliding the synchro hub back and forth. I tried grinding the corners off the spring to give it a little more room to move. No luck. I tried rotating the gearbox mainshaft a little bit to shuffle things around. All that did was mangle the spring and send it flying into the sump.

Life is too short to replace a synchro spring in situ. If you know of a way of doing it, let me know and I'll buy you a drink. If you don't, just take the gearbox out. Honestly, it's easier. Yes, really, it is.

Before you start

This is the bit I wish someone else had written before I started. This is the list of tools that I couldn't have done it without, or at least wished I had had.

Removing the Transmission

I had to face facts. That transmission was going to have to come out. The trouble is, it's very big and heavy, I don't have any clever hoisting equipment, and I don't have anyone to help most of the time. So I'd have to remove it single-handed, in pieces. The first step, however, was to remove the seatbox to allow access to the transmission.

Removing the seatbox would have been straightforward if it hadn't been for two exceptionally annoying bolts, which were so annoying that I took a photo of one of them.

seat belt anchorage

The bolt in question is the highlighted one. It's right down by the door frame and holds both the seat belt anchorage and seat box on to a bracket on the chassis. The bracket has caged nuts in it, and of course they are just solid lumps of rust after 20 years or so exposure to the weather. So when you try and turn the bolt, the caged nut falls apart and you're left with a lump of rust which rotates freely but won't come out. And you can't get an angle grinder to the bolt head because that seat belt mounting bolt is in the way. The only way to undo that is with an 11/16" ring spanner, which I didn't have to hand, so I had to find another way.

Don't try to remove the seat box unless you have an 11/16" ring spanner and an angle grinder handy. It's not as easy as it looks.

Luckily my vehicle, being ex-army, has a removable gearbox crossmember on the chassis. Due to the patented Land Rover anti-corrosion oil leak system, it was delightfully easy to remove the offending crossmember, first remembering to prop the transmission up with a jack and assorted bits of wood. The rest is textbook stuff, except for the requirement for Whitworth spanners, and the need to lower the parts to the ground safely. The only solution to the first is to visit your local tool shop. The second I came up with a neat trick for.

Handily, it relies on having the seat box present, which is convenient since I failed to remove it. Basically, you just put a couple of lengths of wood across the seat box for strength, and sling the appropriate parts of the gearbox from underneath using ratchet luggage straps, like this:

This is the start of the operation to lower the transfer box to the ground. Note how there are two luggage straps. That means you can release the tension on one using its ratchet, lowering the box slightly, then release the tension on the other, and so on lowering the box to the ground in controlled steps.

Here you see it shuffled to one side and a bit lower.

Now it's on the ground on a professional-quality cardboard skid to keep it clean.

Here's the same operation on the main gearbox, viewed from a little further back.

And here, finally, is the object of the exercise: the main gearbox, free of the vehicle.

The main gearbox and transfer box aren't actually too heavy once you have separated them from each other, and can be shifted around safely by one person. The transfer box is just a bit of an awkward shape. Wear good tough rigger's gloves and you'll have no trouble.

The rebuild

The rebuild itself proceeded almost entirely as the workshop manual said it should. Once I had the box apart, it was abundantly clear where the rattling marbles noise was coming from. The big fat ball bearing on the first motion shaft had disintegrated. The bits of mangled steel in the sump were all bits of the bearing's cage: the balls themselves were free to rattle around inside the bearing, hence the noise. It really was rattling marbles. And the huge amount of play in the bearing was allowing the shaft to do all sorts of things it shouldn't, hence the vibrating gear lever. At this point I was very glad I dismantled the box: simply replacing the missing synchro spring would not have fixed the problem.

If your gearbox has a fair few miles on it and is getting rather notchy, it's amazing how much of an improvement replacing the third/fourth gear synchro unit and the first/second gear synchro cones will make. The parts in mine didn't look particularly worn, but I replaced the synchros anyway since I didn't plan to be going in there again any time soon, and the box feels much smoother now.

I did take lots of nice photographs of the rebuild process, but forgot to back them up before rebuilding my PC recently, sadly.

The workshop manual requires you to tighten the mainshaft nut to 100 lb ft and the layshaft bolt to 65 lb ft. However, these are both on the end of shafts which are free to rotate, so you can't get any torque on to them. I came up with a couple of tricks to help out:

If the main gearbox is partially dismantled (bellhousing removed, 3rd/4th gear synchro removed) you can grip the splined mainshaft with a Mole wrench through the top cover hole. Be sure to put some soft metal (copper or aluminium) on the wrench jaws to avoid damage to the mainshaft splines. When you apply torque to the mainshaft nut, the Mole wrench will simply bear against the side of the casing. This is rather hard to explain without the photo, but should be clear when you have the parts in front of you.

If the gearbox is assembled, as it would be when tightening the layshaft bolt, you can "lock" the gearbox by putting it into two gears at once if you haven't put the top cover back on yet. I found it easiest to use reverse and 3rd - slide the reverse idler so it meshes with its mainshaft and layshaft counterparts, and lever the 3rd/4th gear synchro towards the back of the gearbox with a big screwdriver or similar. Now you can apply torque
to the mainshaft and layshaft as long as the gearbox casing is held firmly. Try sitting on it.

I didn't replace the layshaft bearings in my gearbox, and now I wish I had because the rest of it is so quiet that I can hear them, especially in first and second gear. Oh well, next time.

Transfer box

There wasn't actually anything wrong with my transfer box, but since my Land Rover does far more motorway miles than it was ever designed to, I decided to take the opportunity to fit an Ashcroft high ratio transfer kit for more relaxed high-speed (ahem) cruising. I've documented that process on a separate page.


In order to reassemble the transmission there are a number of parts you are certain to need:

I found that the most fiddly part of reassembling the gearbox was reattaching the bellhousing to it. The manuals make it sound easy, but actually it involves lots of juggling of the first motion gears and the layshaft bearing to mesh in the right places as you push the bellhousing into place, and there isn't much room to play with. An extra pair of hands would be useful at this point.

There's always one more bit. No matter how close you think you are to finishing the job, there will always be one more tiny thing you need to actually do it which you haven't got. A stripped nut, or a not-quite-thick-enough-shim, is all it takes for you to have to wait yet another 24 hours for parts. It was only thanks to the unflappable mail order staff at Dingocroft that I managed to get everything together.


I'd read all the horror stories about how painful it can be trying to reattach engines to gearboxes or vice versa, so I'd steeled myself for a long and tiring battle putting the main gearbox back into the vehicle without the help of a hoist.

By this point I'd actually managed to remove the seat box, so I was able to stand in the space where the middle seat should be and offer the gearbox up to the flywheel housing, supporting it with one hand on the gear lever bracket and the other on the output gear. At first it didn't want to go all the way in, presumably because the splines on the first motion shaft weren't aligned with the splines in the clutch. A cunning trick occurred to me, though: by putting the box into gear (I chose 4th because it moved the lever out of the way!) I could rotate the output gear, and hence the first motion shaft, whilst jiggling it into position. It worked a treat - after just a few seconds, the bellhousing slid smoothly onto the flywheel housing studs as the shaft engaged. Maybe it was only easy because the clutch hadn't been disturbed. I can imagine it would be a lot more difficult if the clutch splines weren't aligned properly.

Reattaching the transfer box to the main gearbox wasn't too difficult once I'd worked out that the best way to support the transfer box (which is much heavier than the main box) was to hold the upper end of it and suspend the lower end around the front output shaft housing with a luggage strap. Then it was reasonably easy to shuffle it into place. The main problem after that was that the gearbox mounts didn't line up at all.

To get the transmission aligned with the mounts once it's assembled, use the Land Rover's own screw jack to push the whole transmission (and engine, which it's attached to) against the chassis until the bolt holes line up.

Having got everything back into position and found places for all the orphaned fasteners, the final stage was to put the intermediate gear back into the transfer box and refill everything with oil. That bit went smoothly, apart from having to explain to my local motor factor's why I really did need a gallon of EP90, and that a litre wouldn't do. As soon as I mentioned the magic words, "Land Rover", they gave in. You can read more about the transfer box reassembly on the Ashcroft page.