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.
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.
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.
Whitworth combination spanners. The transmission, being at least partially a 1930s design, is covered with BSW and BSF fasteners. Ordinary imperial AF sized tools just don't fit. The sizes of spanner which came in handy were:
3/16 Whitworth: the little nuts on the studs holding the transfer box sump on, and sundry other fasteners such as the detent spring retainers
1/4 Whitworth: lots of things on the front output shaft housing
5/16 Whitworth: all over the place, but especially on the selector forks and the back of the transfer box. A 15mm spanner or socket almost fits, being rather snug, but just won't go on to some of the nuts.
3/8 Whitworth: the nuts holding the mounting brackets on to the transfer box
There are a couple of larger nuts which I suspect might be 7/16 or even 1/2 Whitworth - the centre detent spring holder and the main gearbox drain plug. They're easy enough to get an adjustable spanner to, though.
Note that for historical reasons the nominal size of Whitworth tools bears no relation to any dimension you can actually measure on either the tool or the nut.
Of course, making everything Whitworth would be just too easy, so you'll need standard AF imperial spanners and sockets too. The most common seem to be 7/16 (sundry bodywork bolts, but beware - quite a lot of mine were 10mm), 1/2 (lots of things, including clutch slave cylinder and lo/hi selector pivot mountings) and 9/16 (fits removable gearbox crossmember bolts, if you've got them, and propshaft bolts).
In order to remove the bellhousing from the main gearbox you'll need a 13/16 AF socket and an extension bar - 4" or so.
A 1 inch AF socket or ring spanner is useful for the castle nuts which hold the propshaft flanges onto the front and rear transfer box output shafts.
In order to remove the seat box, you'll probably have to undo the seat belt mounts by the bottoms of the doors. The only way I could find of undoing these, which were very tight, was using an 11/16 AF ring spanner. An open-ended spanner just slipped off, and there's no room to get a socket in.
Circlip pliers: external are most useful. The bigger the better: mine do 15-60mm and are only just big enough, really. Internal circlip pliers are needed if you're planning to remove the front output shaft bearing from the transfer box, but see elsewhere in this document for why you probably don't need to.
Land Rover special tool #1, otherwise known as a big hammer. Useful all the time, especially for relieving frustration. I found it useful to keep a selection of scrap bits of metal around to interpose between the hammer and the object, which prevents damage. Especially good for this were some bits of copper sheet. I got mine by cutting up and flattening some spare 15mm plumbing pipe.
Mole grips. Again useful all the time, but especially so in combination with a couple of bits of copper sheet on the jaws to grip splined shafts (such as the main gearbox mainshaft) without damaging them. Also handy for pulling locating pegs out of the transfer box casing if you're moving them to a new casing, for example when fitting the Ashcroft high ratio kit.
Torque wrench. All the specified torque settings for things on the transmission
be fairly high, so make sure your torque wrench is accurate up to at least 100 lb ft.
Spring balance, capable of indicating a force of between 2 and 4 lb. You need this for setting the transfer box output shaft bearing preload, or at least trying to set it and deciding it's near enough and you might as well just reassemble the speedometer drive housing with the same number of shims it's already got. You'll also need a length, a metre or so, of nylon string.
Feeler gauges, for setting endfloat on various shafts. Whether they're metric or imperial you'll always end up needing to convert one way or the other.
Vernier calipers. Although not strictly necessary, I found them useful for measuring the sizes of unknown nuts in order to obtain tools to fit them, and also for measuring the thickness of shims which were already present in the transmission to help calculate what other shims I'd need to take up endfloat.
Sturdy workbench and vice. At least, I spent a lot of my time wishing I had one, and built one afterwards with all the free time I had once I had no gearbox to work on.
Blowtorch. Useful for warming things to help undo seized fasteners and so on.
Lots of rags. Try and keep them segregated into "clean" and "dirty" - clean ones for wiping dirt and oil off internal components, and dirty ones for the real filth on the outside of the transmission. This way you avoid transferring a lot of dirt into the transmission where it can do damage.
Lots of pots and boxes to put parts in. You will end up with bits of Land Rover stacked up absolutely everywhere, including dozens and dozens of assorted incompatible fasteners. Try to stay organized and you'll increase your chances of staying sane and not losing anything. Likewise, don't underestimate the amount of space you'll need to work. The transmission, especially separated into its major assemblies, is a big heavy beast.
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.
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 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.
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:
Complete gasket set, part number 600603. The Ashcroft kit comes with one of these, so you won't need to buy another if you're doing the Ashcroft conversion.
Split pins for output flanges.
Lots of EP90 to refill the transmission with afterwards
Molybdenum Disulphide grease for the clutch release mechanism.
WD40, GT85, Duck Oil or something for easing corroded and dirty threads
Oil can full of something oily (I think mine was 15W40 engine oil) to ease assembly of new or cleaned parts
Loctite for those bolts which you really don't want to come undone, notably the layshaft bolt and mainshaft nut. Having said that, the layshaft bolt was completely loose on my gearbox when I dismantled it, so it can't be that important.
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.