RETRO-FITTING PLUS
8 GEARBOXES
by Lorne Goldman OPTIONS LT77 The LT77 gearbox (from the
Rover SD1) has many different reputations. There were many versions made
(A, B, C, D, and S) and the later ones became progressively more problem
free. I have friends with rebuilt LT77s in a 290 HP cars that have
given several years service with many track days and no problems. If you
use an LT77 it is worth knowing the different variations. The LT77
was introduced to Morgans in 1976. It is the same box used with the Rover
SD1. The early boxes are not great. A LT77 variation was introduced to
Landrovers in 1983 with the suffix 'D' box (which was a big improvement)
and was developed over the years to the suffix 'H' which was last used
in 1994. This was improved upon with the suffix E which used a wider reverse
gears. Then came the suffix F which used larger diameter laygear 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. The 'H' (termed the LT77S) was the same as the 'G' in terms of strength but used a different syncro set up called the'Double Syncro', (though in reality it didn't work much better. The LT77 is quite particular about the oil that is used. Rover used to specify ATF (Ford Dextron 3) to overcome baulking when cold. That is very thin oil. There are those who use Redline MTL or Castrol SMX-S with reported success and much smoother shifting. There is a now synthetic oil specifically designed for this gearbox from a company called Difflock. The product is called Difflock Evolution 1 Fully Synthetic 5 speed Gear Oil - 1 litre. These oils are fully synthetic with friction properties designed especially for gear syncros. They reportedly make gear changes like a knife through butter and synchro engagement is really good. The box is rated to 245bft. torque..but this reflects manufacturer caution and Morgans have a VERY light load and the later LT77s (post 1988) are likely stronger.
The World Class T5 'box is rated at 300lbft of torque. (Other T-5s can be considerably weaker). This version is generally acknowledged to be a stronger 'box than the LT77 and is 12 pounds lighter. To fit this you can use a bellhousing for an automatic SD1. This is shorter than the manual bellhousings and can be fitted to the T5 with an adapter plate. The easiest way to operate the clutch is to use a concentric hydraulic release bearing that is attached to the gearbox front over the input shaft. Alternatively, you can buy an aftermarket specially cast bellhousing from John Eales Developments. The advantage with T-5 is easy accessibity of parts and a huge range of gearsets. In the UK, ask for the type used in the TVR. Note the proper gearlever placement R380 Gearbox
There is no need for extensive chassis mods if replacing a Morgan LT77 with a Morgan R380. The bellhousing and remote from the LT77 can be attached to the R380. A small part of the chassis mounting plate for the LT77 will have to be ground away but the new mounting postion arrives at the crossmember making the fitting easy. The propshaft is same as the Morgan R380 is the same length as the Morgan LT77. HOWEVER, the R380 used on the Morgan is a special version made for Plus 8s, later Plus 4s, some TVR Chimaeras and Sherpa vans only. The oil required is a MTF94, either castrol SMX-S, Texaco MTF-94 or Amsoil Synthetic Manual Synchromesh Transmission Fluid (MTF) SAE 5W-30. The R380 corresponds to its load rating in NM or 280 lbs/ft. CONVERSION COMPONENTSPlus 8 4/4 Plus 4 |