I've been doing a bit of pondering lately about the whole issue of gearboxes. The LT77 gearbox from the Rover SD1 has a reputation for being weak (LT presumably stands for Leyland Triumph - Donald Stokes was a Triumph man). Well, maybe that's being a bit too harsh, after all these boxes will allegedly handle over 250 hp and they've been used behind the Rover V8 in countless applications. But it seems their durability is not too good and they cost lots to rebuild. The consensus of opinion among Rover specialists, tuners and enthusiasts appears to be that the Rover box is at best acceptable for a while until something better can be used, at worst a source of recurring trouble which is generally expensive and awkward to fix.

Rover sometimes seems to have a bit of a problem with gearboxes. The LT 77 was developed for the SD1 because the factory's 4 speed was not considered man enough for the job. It was acknowledged at the time (1976) to be quite advanced - 5 speeds, internal oil pump and shafts that ran in tapered roller bearings.

Problems were soon encountered however, most prominent of which was difficulty in selecting 2nd gear when cold. The solution Rover advised was to use Castrol TQF automatic transmission fluid instead of normal EP 80 manual gear oil. This is now a bit contentious as some claim TQF does more harm than good. RPI believe the problem lays with the inferior lubricating abilities of TQF when used in a manual gearbox. According to RPI Rover more recently changed its recommendation again, this time to Castrol SMX (a semi synthetic auto transmission fluid). RPI are not aware of any major misgivings surrounding the use of SMX but it may be too early in the piece yet to make a judgement on its suitability.

The problem of poor/baulking gearchanges on the LT 77 has never really been fully resolved. Land Rover attempted to fix it by introducing the LT 77S 'box with revised synchro cones on the early Discovery, but this did not absolutely overcome the problem. Some people recommend using 20/50 engine oil. I have used ATF and fully synthetic 75W80, but the best oil I have used is Redline MTL. It is fully synthetic with friction properties designed especially for gear synchros. This makes the gearchanges like a knife through butter and synchro engagement is really good.

As we all now know it's very unwise to tow a manual SD1 for any distance because the oil pump does not spin resulting in damaged gears, as many original owners found out the hard way. Longevity of the LT 77's bearings is another worry - the bearings often fail on the shafts on high powered cars, one of the reasons the Vitesse and I believe police spec boxes got beefed up bearings and shot peened gears in an attempt to make them more reliable. And then there was the problem of shearing 5th gear at high speeds (as the works rallying TR8s experienced) allegedly attributed to the use of TQF.

The tapered input shaft bearing and the fibre gear oil pump appear to be the 'box's major weaknesses. According to RPI who have pulled literally thousands of these 'boxes apart, LT 77s are usually well knackered by 120,000km (or less) mainly because the input shaft bearing at the front of the casing moves out of alignment. It seems the tapered roller's tolerance is pre-set by the factory with shims but over time these allow the input shaft to become slack within the front cover causing it not to mesh correctly with the layshaft. In bad cases the input shaft bearing can seize, then the cluster shaft tears all its and the input shaft's teeth off. Rover made a few changes to the box over the years but none really solved the problem. I believe the D suffix box from the Vitesse is the strongest. This has slightly stronger internals than the earlier 'boxes and is fitted with a higher 5th gear - 0.793 instead of 0.833.

There are, for better or worse, a number of alternatives which can be used in an SD1. The later factory R380 gearbox as fitted to the MG RV8 and later Discos is supposed to be a nicer 'box to use and reputedly stronger and it will slot right in to where an LT 77 was fitted (RPI are now selling these exclusively as replacements for the LT 77). But what RPI don't mention is that there have again been durability issues with the R380, with failures not uncommon on the manual V8 Discos (the evidence is on Land Rover forums). Many Disco owners had to get their 'boxes repaired under warranty by Land Rover. Maybe they last longer in sedan cars than they do in 4 x 4s?

The Ford Cosworth BW T5 is another option favoured by some (including TVR after they gave up using the Vitesse 'box) but there have been reports of this box stripping gears when used in anger on high powered Rovers and suitable bellhousings are very expensive and not easily come by. Many hotrodders in the UK consider the T5 to be not much better than a good Rover gearbox. Getrags are of course another option but they're expensive to buy and fix and noisy. The Tremec gearbox is strong but costly, and I'm not aware of a kit to fit them to a Rover. I have also seen a Muncie and a Ford top loader used in some applications, but these are quite rare combinations and require special bellhousings, rear mounts, and so on.

The one effective solution to all this despair and disrepair is to replace the Rover 5 speed with a Toyota Supra unit.

The Toyota 5 speed alloy cased gearbox is tough, lightweight, common and cheap. It needs to be fitted up using the a good installation kit like the one Dellow Automotive in Sydney produce which contains everything needed including the bellhousing, tailshaft yoke and clutch components for around AUD800. Dellow can also supply a recon or low mileage Supra box ex Japan for around AUD600 or owners can source their own. This is all quite reasonable compared to the price of a recond LT 77 or a new R380 (which is almost as bad). As an added bonus the kit enables you to get rid of the SD1s non serviceable CV joint tailshaft and use regular universal joints.

The so-called 'oval case' Supra 'box is almost the same size as the Rover one but weighs only 33 kg compared to the Rover's 50 kg. It comes in four versions with differing gear ratios. Of these Dellow recommend either a W 55 or a W 59 box - there's also a W 57 and W 58 but these have a 1.89 second gear which is not really appropriate.

Ratio W55 W57 W58 W59 R154 RoverVitesse
1st 3.57 3.28 3.28 3.95 3.30 3.32
2nd 2.06 1.89 1.89 2.14 1.95 2.09
3rd 1.38 1.27 1.27 1.27 1.34 1.40
4th 1.00 1.00 1.00 1.00 1.00 1.00
5th 0.85 0.86 0.78 0.83 0.75 0.79

In addition there is the R 154 'box as fitted to the Supra twin turbo. This has appropriate gearing but is wider and heavier than the non turbo boxes, though it's virtually indestructible (also has an electric speedo drive). The Celica steel case box can also be used but this is generally agreed to be not as good or as strong as the Supra box, and of course it's heavier. And lastly there's the Supra V160 box which is a 6 speed and actually a Getrag box but I believe the bellhousing is integral to the gearbox on this which would present problems.

Some diehard Rover fans will no doubt find the idea of using the Jap box repugnant, but it does deliver the goods for a reasonable investment, and at least you can't see it too often! It's also a tried and tested conversion and all the reports I've read from people who have done it have been positive (nearly all had experienced breakages with the LT 77). Some, it must be said, only turned to Toyota as a last resort out of desperation and sheer frustration with the failures of the Rover products.

Very interesting, i was only thinking yesterday about the Supra box and asking some question about it but you seem to have covered it all. Which Supra though? i take you mean the last shape? It's just a csae now of finding someone over here that knows about it, and selling everything i need.

Have a look at Dellow's website - they can supply everything needed for this conversion and can advise on the most suitable box for whatever application (road / track).

Can you post up the Link please?

Try:

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Other sources in Oz are Triumph Rover Spares in Adelaide and Castlemaine Rod Shop Conversions in Victoria.

My autobox seal which connects to the intake manifold is leaking causing the engine to suck up the gearbox oil and dump it in the sump..Any one else heard of this..?

Ive got a 4 speed Jaguar box (Auto)

Thats the problem exactly..!!
Do jag gearboxes fit....BTW?

You need a Range Rover bellhousing (quite common) the dip stick needs changing side, the kick down is either Jag or Range Rover. When it mounts it is tilted a little, so it has to go quite high. Another problem is speedo drive, the box doesnt have one, you can get one from A Leylan Daf van but are expensive. Well worth the mod though. My mate has a P5 that he done years ago, one of the first.

My 79 V8s is on its original box, it has the usual weak syncro on second when cold but otherwise its fine and is the original.

Hi All very interesting ....... can you help. I have a P6 3.5 fitted in a Lotus but the guy that had the car before me did not connect the speedo cable. I have looked at this and can see why. There is not enough room for the cable to bend round only about 60 mm before hitting the chassis. What I want to find out is do any of the Rover gear box's use an electronic system? or has any one ever converted the manual one to electronic? Where can I find information about this on the internet? The other problem I have is the reversing light I have not got one? Is the switch inside the gearbox? There is not a lot of room around the gearbox and I cant see any connections? Thanks for your help.