Almost but not quite perfect timing
Fenchurch's first gear has been gradually deteriorating for months - very noisy, and jumping out of gear on acceleration. I received a replacement gearbox yesterday and was planning to fit it this weekend, but when I set off home from work today it went "bang" and nearly bust my finger, so hard did it kick the stick out of gear. The rest of the gears still worked so I drove home using second gear instead of first and slipping the clutch a lot (I'm replacing the clutch at the same time as the box so I didn't care if I burnt it out). It's lucky my dad was able to collect the box when he was near Birmingham on a business trip because my original plan was pick it up myself in a couple of weeks' time when I go down there for Novacon.
So tonight I pumped the water out of the inspection pit under the garage, drained the oil out of the old box (cue several "plopping" sounds as shiny bits fell out), removed the prop shaft, took the front seats out, and removed the gearbox cover. Tomorrow I'll be bussing to work again, then getting on with removing the old box in the evening. I'm planning to do it without removing the engine, despite advice that it's much easier to do it that way, because I'm a cheapskate and don't want to hire a crane for the weekend.
So tonight I pumped the water out of the inspection pit under the garage, drained the oil out of the old box (cue several "plopping" sounds as shiny bits fell out), removed the prop shaft, took the front seats out, and removed the gearbox cover. Tomorrow I'll be bussing to work again, then getting on with removing the old box in the evening. I'm planning to do it without removing the engine, despite advice that it's much easier to do it that way, because I'm a cheapskate and don't want to hire a crane for the weekend.
I did it in five hours without a pit- in fact, I could have done it on level ground. It's possible to remove and replace the gearbox via that inspection cover in the floor- with a careful twist it will come out from above, which I had to do anyway as the crossmember had been welded in.
You were right about the cause of the fault. The layshaft is a bit rough in one spot (enough to account for some of the noise), but the big spur gear is very badly worn/chipped (every tooth) and the small spur gear is pretty much completely trashed. It's clear now why it pushes out of gear on acceleration too - when you crash it into gear it chips a particular corner off the teeth. Do it enough times (hundreds) and the teeth wind up tapered in such a way that when a force is transmitted through them it tends to push the big gear back towards the neutral position. I'll post pictures tomorrow...
I got to the upper bellhousing bolts from above- it's a bit of a contortion but less prone to making your arms ache. You have to remember to do it before you lower the engine, though, as it backs up against the member that takes the shock absorbers.