Disco – gearbox fettling

The second gear synchromesh on the Discovery’s gearbox is very worn. Synchromesh is magic stuff that acts just before you engage a gear, to bring the relevent cogs up to the required speed for a crunch-free change. In the old days, you used to have to try and do this yourself by double-declutching. I’ve been having to do that in the Discovery as the gearbox is shagged – that’s a technical term.

At 179,000 miles, perhaps that’s not surprising. Especially when you consider that the LT77 transmission used in the Discovery was actually developed for the Rover SD1 and Triumph TR7 – both launched in 1975. Yup, yet another component ‘borrowed’ from elsewhere on this marvellous parts-bin special. When people started having gearbox issues, even when these units were young, Rover changed the recommendation to automatic transmission fluid. I opted to use modern, synthetic Dextron III transmission fluid thinking that perhaps a posh fluid might improve the gearchange situation. Gearboxes are very sensitive to the right fluid – too thick and the synchromesh just won’t work at all.

Annoyingly, I had to borrow an enormous 32mm spanner from a neighbour to get the huge sump plug undone. Before I did this, I did of course ensure that I could undo the filler plug – a 13mm spanner handled this. Once the main part of the gearbox had drained, I undid the plug on the extension piece. I don’t know much about the construction of these gearboxes, but this is apparently where fifth gear lives. It is NOT the transfer box – that’s yet another box of cogs. The extension drain plug has a filter above it which needs to be removed and cleared out. This was done.

The stupidly huge sump plug on the other hand has a magnet in it. This is what it looked like when I removed it.

Land Rover gearbox plug

Sauron – Lord of the Synchro Rings

That’s a LOT of metal filings. You always expect a few – every time you crunch the gears, you’re chipping bits off the teeth – but this seemed quite bad. Not that surprising when you consider that the previous owner just crunched into second gear every time. I at least try to avoid a crunch by double-declutching.

With the plugs back in, I could refill the gearbox with my lovely new fluid. I used a pump with a long tube on it to get the fluid in, as there’s no way you can get a bottle high enough to fill it directly. Internet research before the job definitely paid off! Once the new fluid was in, I could head for a drive. There was a definite improvement. If I take it easy, I can now change from first to second without a crunch, even when the gearbox is cold. Third to second is still a bit of an issue though, so the problem has not entirely gone away – not that I really thought it entirely would.

While out on the test drive, I stopped off at a friend’s house and he helped me remove the side steps. I should have done this sooner really as it is now MUCH easier to crawl beneath the vehicle!

Discovery 3-door

Steps begone! A vast improvement

I think it looks much better without them. The steps had near enough rotted away anyway and they massively compromise off-road ability. The break-over angle is now much higher. I also hated the way that the sill, which actually sweeps up slightly towards the front wheelarch, left an ungainly gap because the side steps were entirely flat.

I also filled up the Disco the other day. It was reading just below a half on the gauge, but it’s a big old tank! I still got over £60 worth of fuel in, which allowed me to calculate that it has delivered 28mpg so far. That’s not bad at all for a mix of motorway, local roads, greenlaning and tinkering where the engine was left running for long periods.

Next up for the Discovery is a rather more challenging greenlane run this Saturday – the fabled Strata Florida.


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