Manual Boxes quick links
Manual Transmission - How it works.
A Manual Transmission provides a range of forward gears to be selected, according to opposing forces and desired economy. It also offers a means of reversing the vehicle, and a neutral position providing a permanent break in transmission.
To reduce the skill required by the driver to produce a quick, quiet gear-change, synchromesh units were devised which aimed at synchronising the two halves of gear engagement dog clutches, before the dog teeth made contact, by the use of cone clutches.
Some transmissions can also provide a power take off (PTO) point.
Synchromesh unit - How it works.
The Synchromesh unit it the part of the manual transmission that allows the driver to make seamless gear changes, without the "grinding" that you would associate with older gear boxes.
Synchromesh units were devised to reduce the skill rerquired by the driver and to produce quick quiet gear changes.
They aim at synchronizing the two halves of the gear engagement dog clutches, before the dog teeth made contact, by use of cone clutches.
How a DSG
(Dual clutch transmission) works.
A Direct Shift Gearbox (DSG) is two separate manual gearboxes (and clutches) contained within one housing and working as one unit. By using two independent clutches, a DSG can achieve faster shift times and eliminates the need of a torque converter in a conventional epicyclic automatic transmission.
The engine drives two clutch packs. The outer clutch pack drives gears 1, 3, 5 (and 7 when fitted), and reverse — the outer clutch pack has a larger diameter compared to the inner clutch, and can therefore handle a greater torque loading. The inner clutch pack drives gears 2, 4, and 6. Instead of a standard large dry single-plate clutch, each clutch pack for the six-speed DSG is a collection of four small wet interleaved clutch plates (similar to a motorcycle wet multi-plate clutch). Due to space constraints, the two clutch assemblies are concentric, and the shafts within the gearbox are hollow and also concentric. Because the alternate clutch pack's gear-sets can be pre-selected (predictive shifts enabled via the unloaded section of the gearbox), un-powered time while shifting is avoided because the transmission of torque is simply switched from one clutch-pack to the other.
LandRover LT77 & R380 Manual Transmissions
The LT77 & R380 transmissions were most commonly fitted to Land Rovers.
The LT77 was generally fitted to vehicles from 1982 to 1994, and the R380 was fitted from 1995 to around 2007.
The LT77 is an updated version of an old Jaguar gearbox that found its way into current model British cars manufactured by British Leyland. The LT77 gearbox was so named because the distance between the main and lay shafts is 77 mm.
There were two version of this gearbox. The earlier version is known as the short stick version. The later version, introduced around 1988 is known as the long stick version.
The R380 box (So named because it is rated to 380 Nm of torque) was introduced as brand new LR gearbox across the entire Land Rover and Range Rover product lines. The R380 is a reworked LT77 with improved main shaft bearing arrangements that provided an overall strengthening of the box. The R380 still has the LT77’s 77 mm shaft spacing.
Since Rover was no longer part of British Leyland the LT prefix was abandoned.
