by Lorne Goldman



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.  Some have  stronger internals than the earlier 'boxes and are fitted with a higher 5th gear - 0.793 instead of 0.833. Morgans mate the box to a modified Sd1 bellhousing with and one of three Sd1 remote gear lever assemblies.

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 bearings. The suffix G was uprated with all the gears being widened. Then the last of the LT77 was the suffix H (also known as the LT77S( It used a dual synchro on 1st and 2nd gear. The best version is the last, the LT77S..or those with the G or H suffix. YOU NEED A SD1 VERSION.

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.  

CRITICAL  WATCHPOINT: It used to be common knowledge for all owners, but it has been years since classic production ended and the current generation of owners and Morgan staff are not familar or interactive with Morgans anymore, as the crowd of the first hundred years were. Perhaps this will change when the latest generation of humanity dies off. Until then, the cars will be super vulnerable to their ill-chosen public gurus and local mechanics.

The LT77 uses an unusual internal oil/lubrication pump. It is not only very sensitive to oil viscosity, which is the reason, after a plague of failures when it was first used, they finally settled on Dextron 3, an automatic gearbox fluid (!), for these units as the feeble little internal pump could deal with it. Of course, the LT77s did become much stronger as time went on, but the automatic fluid is always called for. 25 years ago I damaged a LT77 sufficiently to require a full rebuild after driving 10 kms with the wrong fluid. :(

TOWING a LT77 vehicle with the rear wheels on the ground is also a BIG no-no for the same reason...the internal plastic pump. The R380 is a completely different fact, stronger than the conservative 380nm it is named for. (440nm or 325 ftlbs) However, there have been reports that 5th gear can be damaged by towing with the wheels on the ground. Use a tow truck that lifts the entire car (they are much safer for all cars) or, alternatively, lock the steering wheel and tow by lifting rear wheels off the ground. 

Borg Warner T5 Gearbox

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

The R380 is a development made to replaced the LT77s. Same gear set as the LT77. It was fitted to the MG V8 and the latest Land Rovers from 1994 to 2002 but not in a Morgan configuration. 

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.   


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