Replacing the R380 gearbox
Trevor Cuthbert reports on removing a faulty R380 gearbox and fitting a new refurbished unit
How to remove a faulty Discovery (1&2) and Defender ’box and fit a refurbed unit
THE R380 5-speed gearbox as fitted to 300Tdi/td5 Defenders and manual models of Disco 1 (‘94-on) and D2 is a generally reliable and long-lived unit, which gives a very good service life. That assumes it is not abused and receives oil changes at least within the specified service interval. These gearboxes can last well over 150,000 miles, depending on usage. For example, the gearbox in a Land Rover that does frequent and heavy towing would be expected to begin to fail sooner than one that does not tow. However, the life of a gearbox can also be dependent of the driving style and sympathy of the driver. Again, a gearbox that is driven hard (fast acceleration and quick shifting) will show signs of wearing out sooner than one driven more sedately.
One of the common characteristics of an older R380 gearbox will be a crunch of gears, as the driver shifts from first to second gear. This is related to the second gear synchromesh in the gearbox and arises because it is often the fastest shift a driver makes and can be one with the greater loads involved, overcoming inertia as the Land Rover accelerates. The second gear crunch can be reduced by gentler first to second gear shifts and double declutching will also overcome the effect. I have known several Land Rover owners, over the years, who have lived with the second gear crunch for many thousands of miles and the issue does not necessarily spell the immediate end of a gearbox, but serves as a warning that it is getting on a bit.
More serious on the early LT77 gearboxes was a clunk when the drive was taken up, due to worn mainshaft splines. This caused movement between the
mainshaft and the transfer gear that drives the transfer box. In severe cases of mainshaft spline wear drive could be completely lost. The problem was poor lubrication of the splines and was corrected on later transmissions by using a cross-drilled transfer gear that allowed oil through to the splines. It’s unusual to find this nowadays because most gearboxes have been rebuilt with the later cross-drilled gear. To check for mainshaft spline wear remove the PTO cover and with the main box in first gear rock the Land Rover backwards and forwards while looking into the end of the input gear. If the spline is worn you will see the movement, described earlier, of the shaft in relation to the gear.
There are other causes of clunk in a Land Rover, of course – for example wear in the A-frame ball joint (not in Discovery 2) or wear in the halfshaft drive flanges. Difficulty in shifting down to fourth from fifth and having to nudge third gear first, is due to the synchro gear being blocked by the baulk ring rotating too far – a problem in earlier gearboxes that requires a rebuild.
In this particular Discovery 2, the owner had been experiencing the second gear crunch for some time, which he had been living with. But more lately the synchromesh was failing when shifting up to fourth gear. He decided that it was time for a gearbox change.
Safety first
1 When carrying out any repairs to a motor vehicle, it is good practice to disconnect the battery to avoid any short outs or electrical issues.
Avoid contact
2 As we will be tilting the engine, the fan is removed so that it will not foul and damage the radiator during the course of the work.
Strip the sticks
3 The hi-low shifter and gear lever knobs and covers are carefully pried from the centre console, and the gear lever is unbolted and removed.
Right way round
4 The electric windows switch panel is unscrewed and the wiring harnesses unplugged, with the driver’s side marked with a green cable tie to avoid mix ups.
All needs to be separated
5 The wiring to the gearbox and transfer box is unplugged from the main loom and pushed through the transmission tunnel, with the sealing grommet.
Allow it to drop down
6 The hi-low shifter assembly is fixed to the transmission tunnel by four M6 bolts. These are removed with an 8 mm ratchet spanner to free the shifter.
Drilling is the only option
7 Blind rivets securing the gear lever rubber boot to the transmission tunnel are drilled out with a 5 mm drill bit, then the boot is pulled out.
Draining the oils
8 On the lift, gearbox and transfer box oils are drained. The gearbox oil looks very milky – a sign that water has mixed with the transmission fluid (MTF94).
Gearbox debris
9 The gearbox bung that was removed to drain the fluid is magnetised to catch metal particles. Not a bad example, but the fluid had been changed recently.
Strip down
10 To remove the transfer gearbox, both propeller shafts need to be removed (9/16 AF), as does the gearbox cross member which is directly below the box.
A heavy lump
11 To lighten the load of the transfer gearbox, the transmission brake drum was pulled off and the brake assembly unbolted, with a 15 mm impact socket.
Set aside
12 The transmission brake assembly was simple to remove completely because the handbrake cable had been disconnected inside and pulled through.
Separate them
13 With all of the bolts holding the transfer gearbox to the main gearbox removed, the transfer box is eased off, supported by the transmission jack.
Precarious
14 The transfer gearbox is lowered by the transmission jack and lifted off to the ground. This is much easier and safer with a second pair of hands.
Worst seen
15 Now we see the mating face of the gearbox, showing severe corrosion around the oil pump, as the drain channel to the right has been blocked.
Pry it off
16 The gearbox is gently eased away from the engine using a pry bar. It’s fully supported on the transmission jacks, with a jig bolted between jack and bellhousing.
Going down
17 The gearbox is lowered on the jacks until it is at a safe height to lift off and down to the floor, without undue risk, as pictured.
Make it easy
18 The gearbox can be set up vertically on a bottle crate, with the output shaft through one of the many holes in the crate, ready to be worked upon.
Unusual wear
19 The old thrust bearing (right) is damaged – it seems the clutch fork was not properly located on it, which would not have helped smooth shifting.
Get most of it away
20 We’ve unbolted the bell-housing from the original gearbox and we’ve given it a clean to remove excess grimy deposits using brake cleaner fluid and blue roll.
Won’t make much difference
21 The new gearbox (refurbished from Ashcroft Transmissions) is supplied without oil. It is easier to fill it while on the workbench, adding relatively little weight.
We need the old bits
22 The ancillary components, such as this reserving light switch and breather tubes, are transferred over from the old gearbox to the new unit.
Taking shape
23 Here the bell-housing is being tapped onto the new gearbox, after the locating dowels have been transferred over. It is then bolted firmly in place.
A little dab of grease 24 The new release bearing is fitted in place with the clutch fork and a new operating rod. The clutch fork has a bolted clip to hold it on the swivel ball. Off and out with the old 25 After removing the dual mass flywheel, the crankshaft spigot bush (locates the gearbox input shaft), is removed and a new bush tapped into place. Genuine parts 26 A new dual mass flywheel is offered up to the engine and carefully positioned over the locating dowel and tapped home onto the crankshaft. Glue them in
27 A set of flywheel bolts are given a drop of thread lock compound, immediately prior to being fitted in place to attach the flywheel.
Follow the sequence
28 The bolts are tightened by diagonal selection to 40 Nm (30 lb-ft). Once all are torqued, they are tightened by a further 90 degrees.
There is a wrong way
29 The clutch friction plate is offered up next, using a section of gearbox input shaft as an alignment tool, taking care to fit it the correct way around (flattest side to the flywheel).
Concentricity
30 The temporary alignment tool holds the friction plate until the pressure plate is fitted, ensuring the gearbox shaft will pass through engage with the crank spigot bearing when refitted.
Correct procedure
31 The new clutch pressure plate is fitted over the friction plate and onto the flywheel, tightening its bolts evenly and progressively to avoid distortion. Alignment tool is then removed.
It is tricky but it will go
32 After a degree of jiggling and striving for correct alignment, the new gearbox is fitted on to the back of the engine and the bell-housing bolts tightened in place.
Minor but important detail
33 Before the transfer gearbox can be re-fitted, the oil seal needs to be changed. Here it is levered out, taking care not to damage the casing.
Get it straight
34 A new oil seal is tapped into place. It is important to ensure that is inserted evenly to avoid damaging it and spoiling its effectiveness.
Make it easy on yourself
35 The transfer gearbox is set up in roughly the correct orientation (angled) on the transmission jack and then raised up towards the main gearbox.
More jiggling
36 The gearbox output shaft can foul the new oil seal if not entered accurately. As it slides home, the drive flange is turned to engage it on the shaft
Secured at both sides
37 When the transmission is bolted together, the chassis mountings brackets are re-attached to support them before the transmission jack is moved out.
This could be messy
38 The transfer gearbox is filled with EP90 gear oil, using a syringe-type oil filler, until the oil level reaches the filler plug height.
Everything back in place
39 The exhaust, gearbox crossmember and transmission brake assembly are refitted, followed by the propshafts with new 3/8 inch UNF bolts and nylock nuts.
Time to go back inside
40 Back inside the cab, the wiring is reconnected and the gear levers and interior trim are refitted. A final check around and the Discovery is ready to go.