Shift Improvements

In order to reduce the problems with 1 - 2 shift, a number of syncro improvements have been made, one of them being we fit stronger syncro springs, this makes the baulk ring bite the gear better to stop it "grinding" into gear.

LT 77 Development

The LT 77 was introduced to the Landrover range in approx 1983 with the suffix D box and was developed over the years to the suffix H which was last used in 1994.

The D and E are very similar the only difference being the reverse gear was a little fatter in the E,

When they went from E to F larger layshaft bearings were used.

The G was further improved by all the gear teeth including the pinion getting approx 20% thicker. Also a much wider pump was used to increase the lubrication and cope with the fact that some of the LT 77"s were now being supplied oil cooled, ie V8 NAS 90, 3.9 RR Classic and the 3.5 EFI Discos.

The H (termed the LT 77S) was the same as the G in terms of strength but used a different syncro set up called the "Double Syncro", In reality it didn"t work much better.

Upgrades to the R 380

Should the LT 77 fail on your vehicle you will usually have the opportunity to replace it with a later R 380, unfortunatly surcharges will apply but if you are either planning to keep the vehicle, working it hard for a living or going on an overland trip where both reliability and the facility to add an oil cooler are important then this additional expenditure may well be worthwhile.

Bias Adjustment

It is important to check the bias adjustment particularly on the defender boxes if a "notchy" selection on 3rd or 4th is a problem.

The bias plate and springs are pre set on the (short stick) Disco and Range Rover boxes, so should need little or no attention, but if there is a problem selecting 3 or 4 it is possible to move the spring location plate which is held down by the 4 x M8 bolts under the top dust cover. If there is a selection problem with 1 - 2 gears there are shims under the "reverse stop plunger" which can be changed. It is surprising how just a small shim change 0.5mm can radically alter the shift.

The "long stick" boxes, Defender and early Range Rover, come without the "turret" assembly. Always check the turret is in good condition ie locates in the socket and feel firm. The 3 and 4 selection is by two "bias" adjustment springs located one each side of the turret under the rubber boot. Pull the boot back and if necessary adjust the two M6 screws under the springs, the lever should self center in the 3 - 4 position. If there is a selection problem with 1 - 2 gears there are shims under the "reverse stop plunger" which can be changed. It is surprising how just a small shim change 0.5mm can radically alter the shift.

The oil viscosity has a very marked effect on the effectiveness of the syncro baulk rings, before the syncro cone can grip the gear,which it must do, it must first push out the oil from between the mating surfaces. If the oil is too viscous it cannot escape from under the baulk ring hence poor syncro effect, this is particularly critical in the LT77 as "sintered" baulk rings are used which give a much greater contact area, giving better grip, but are less effective at oil removal.

Other causes of poor selection are "draging clutch" and "tight spigot bush", both of these problems will show by "crunching" when selecting reverse gear.