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Range Rover Gearboxes

By Andy Grafton

1. General Description and Hearsay
The 4 speed gearbox used on early Range Rovers (until about 1983, when it was superceded by the LT77), the Stage One Land Rover, early Defenders and the 101 Forward Control. It was the first Land Rover gearbox to incorporate a differential in the transfer box, allowing the propshafts to be driven simultaneously at different speeds and thus allowing the use of permanent four wheel drive. The LT95 designation refers to a 95mm spacing between the mainshaft and layshaft.

The LT95 is believed to be the strongest manual gearbox fitted to a production Land Rover and has been successfully mated to engines with high power outputs. All the components are oversize and have a distinctly agricultural feel about them. The gearbox drives much like one from a truck; racing gear changes are not really an option unless you have a very strong arm.

Very early units have a limited slip differential and a differential lock fitted. Throughout early production the limited slip unit remained as a factory option. On most models it is necessary to have the engine running when engaging or disengaging the differential lock as a vacuum from the inlet manifold is required to do so. The lock can be engaged or disengaged at any speed but should not be engaged when the vehicle is turning a sharp corner or has one or more wheels spinning.

An overdrive is available for the box, which fits in place of the PTO cover. It is a lot more rugged than the unit fitted to Series vehicles but is hampered by a low oil volume and tiny bearings. Its use is only recommended in 3rd and 4th gears high range.

2. Technical Details

The gearbox and transfer box are both part of the same casing, which can make removal and overhaul of the 'box a pain. The complete gearbox assembly is exceptionally heavy and bulky and its removal should be well planned. Fortunately, the transfer gearbox, reverse idler gear and some of the selector mechanism can be overhauled with the gearbox in the vehicle.

There is synchromesh on all the forward gears, but not on reverse.

The mainshaft is fed with oil by an oil pump driven off the front of the layshaft. There is a plastic oil filter cum strainer located behind the filler plug which should be extracted and cleaned at each service.

The centre differential came in a number of flavours over the years. The limited slip and standard diffs are the most common, but other variations like a "clonk limiting" diff with spring loaded plates to take up wear have been found. On most vehicles the differential is locked by a vacuum operated system, but on some types a mechanical lever was used. Conversion to a mechanical system is popular as the vacuum system tends to go wrong quite often. Once selected, the vacuum operated diff lock should stay where it is when the engine is switched off, because there are little selector balls designed to keep it that way.

2.1. Lubrication

2.6 litres / 4.5 imp. pints / 5.5 US pints

Transfer box
3.1 litres / 5.5 imp. pints / 6.5 US pints

Early boxes with a limited slip differential:-
Gearbox - Hypoid gear oil, viscosity SAE 80EP to API GL4
Transfer box - Hypoid gear oil, viscosity SAE 90EP to API GL4 Later boxes:- Gearbox - Multigrade engine oil, viscosity SAE 20W/50 to API SF or SG Transfer box - Multigrade engine oil, viscosity SAE 20W/50 to API SF or SG

Oil changes and checks (gearbox and transfer box)
Oil change 1,000 miles (1,500km) after overhaul and thereafter every 24,000 miles (40,000km) or 2 years.
Check oil every 6,000 miles (10,000km). Under severe wading conditions, check level daily or weekly and drain and refill monthly.

2.2. Gear Ratios

Top - Direct
Third - 1.505:1
Second - 2.448:1
First - 4.069:1
Reverse - 4.069:1

A number of ratios were used in different applications. These for the standard 2 door Range Rover.
High - 1.113:1
Low - 3.321:1

3. Problems

The gearbox is extremely rugged, and will perform well in even the most demanding applications. The most fragile part is the centre differential, which can be damaged if the gearbox is used in low-traction situations without the differential lock engaged. It is recommended that the differential lock be engaged if there is any doubt about whether or not it should be. The mode of failure of the centre differential is usually seizure due to overheating between the planetary gears and their shafts or the casing, but mechanical failure of the planetary gears also occurs.

Disengaging the diff lock, engaging the handbrake, revving the engine to 5,000 rpm and then dropping the clutch to spin the front wheels and cover a companion with mud will have a negative effect on the life of the centre differential.

The reverse idler gear is another weak point and it is recommended that full throttle openings and/or high engine speeds in reverse gear low range should be avoided. Jerky tow starts in reverse are apparently not a good idea, and when snatching vehicles use forward gears wherever possible.

Some parts of the gearbox wear relatively quickly. They are as follows;

The splines on the rear of the mainshaft and the splines on the inside of the transfer gear which bear on them. Evidence of this wear is excessive backlash in the transmission. That measurement is highly subjective; most would describe the backlash of a new box as excessive. Eventually the splines wear right through and the car goes nowhere. Removal of the PTO/overdrive cover allows one to check the amount of play the transfer gear has on the shaft.

The centre differential wears quickly if the vehicle is driven in low traction situations without the differential lock engaged. Evidence of this wear is excessive backlash in the transmission. The backlash associated with the centre diff can be gauged by observation of the play in the diff after removal of the transfer box sump.

Shims in the transfer box wear and it will need re-shimming from time to time. This involves removal of most of the transfer box guts. Evidence of this wear is excessive play in the transmission, and the degree to which this is caused by fore/aft movement of the transfer/intermediate gears can be gauged by removing the transfer box sump and getting in there with a crowbar.

Synchros wear out and need replacing. If the vehicle starts to pop out of gear then it is probably thanks to a worn synchro unit and its interface to the main gearwheels. Worn synchros will also contribute to backlash in the transmission.

The bearings are usually very good but will need replacing over time, particularly if the gearbox is used in high-load scenarios or with big engines. Grinding vibrations/noises when the vehicle is cruising or being accelerated may indicate worn bearings. Guess what? Worn bearings will contribute to backlash in the transmission. You were waiting for that, eh? The vacuum actuated differential locking mechanism is prone to problems. The vacuum switch in the cab, diaphragm in the servo/actuator unit and vacuum pipes all suffer over time. The switch on the actuator housing (which illuminates the Diff Lock light) is independent of the actuating mechanism, which is a good thing because when it is working it gives you an indication of what the diff lock is actually doing. It is not unusual for the diff lock to decide to do something completely contrary to the setting of the knob in the cab. The switch for the indicator light also goes wrong, so if it doesn't illuminate when you think it should, check Lucas first.

There are a huge number of points above which contribute to backlash in the transmission. When all the factors combine, the actual amount can be spectacular. That does not necessarily mean that there is anything wrong with the gearboxes.

4. Points of Note

4.1. How can I tell if my Diff Lock is engaging?
The age old question. There are several ways to go about checking but the following are probably the best. This only applies to vehicles with a selectable center diff lock, a non-limited slip centre differential and standard, open axle diffs. If your Range Rover does not have a diff lock knob/lever, you are unsure whether it does, you think you might have a limited slip centre diff or you have axle diff locks then method c) is the only one you can use easily.

a) Disengage the diff lock. Chock the rear wheels. Put the transfer gearbox in Neutral. Jack up one front wheel so it is just off the ground, and try to rotate it by hand. The wheel should spin fairly freely. You can check the observation by selecting low range first gear and letting up the clutch with the engine idling. The wheel in the air should spin, slowly, and the car should go nowhere. With the gearbox in Neutral, engage the diff lock. The wheel in the air should now no longer spin by hand when the transfer gearbox is in Neutral. The vehicle should try and drive itself over the chocks and off the jack if first low is selected.
b) Remove a propshaft. Try and drive. The vehicle will move if the diff lock is engaged, and won't if it isn't. Simple, really.
c) Find a tarred carpark and get an accomplice to drive the car in little circles with the steering on full lock. If you notice the wheels scrabbling, slipping a lot and perhaps chirping as they spin then the diff lock is engaged. If there is no scrabbling then it is not engaged. When the diff lock is engaged there may be some very interesting noises from the transmission as a whole, which is why this is down as option c). Clicking and pinging from the front wheels is worn CV joints, clicking and pinging from underneath is worn universal joints, and a large bang accompanied by grinding and loss of motion is something expensive breaking.

4.2 General Points

The hand brake drum is held on by two small screws and the propshaft bolts. It is highly recommended that the propshaft nuts be replaced if the vehicle is operated without the rear propshaft fitted, as two small screws vibrate loose very quickly. If the propshaft nuts are not there, the heavy lump of metal exits the vehicle with some violence and may make handbrake-shaped holes in sheep standing by the side of the road.

When the vehicle is driven with one propshaft removed, it is essential that the differential lock be engaged. Otherwise you'll go nowhere or burn out any limited slip doodads in the gearbox. If you don't have a centre difflock, you should probably be towing it home with both propshafts removed.

The Haynes Manual has a quotable quote which is particularly applicable to this gearbox.

Note: It is sometimes difficult to decide whether it is worthwhile removing and dismantling the gearbox for a fault which may be nothing more than a minor irritant. Gearboxes which howl, or where the synchromesh is worn but double declutching can overcome the problem, may continue to perform for a long time in this stage. A worn gearbox usually needs a complete rebuild to eliminate noise because the various gears, if re-aligned on new bearings, will continue to howl or begin to howl when different wearing surfaces are presented to each other. The decision to overhaul therefore, must be considered with regard to time and money available, relative to the degree of noise or malfunction that the driver can tolerate.

i.e. if it ain't *really* broke, don't fix it.

Copyright Dixon Kenner, 1995-2011. Last modified September 23, 2007.
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