Just a thought, but when the gearbox was out, did anyone check the condition of the spigot bearing in the rear of the crankshaft?
It’s very easy in an I shift to leave it idling in gear for long periods, which is very hard on the spigot bearing. It may have no effect here, but with some boxes, if the first motion shaft, which is the one which protrudes from the front of the gearbox and passes through the driven plate of the clutch, then into the spigot bearing in the crank, is able to wobble even slightly, as a result of a worn bearing, it can be enough to cause certain gears to disengage under light load, or in overrun conditions.
(The clutch needs to be disassembled in order to check the bearing)
I hope you’ve cracked it, but if not, this may be worth a try.
Good luck!!
Dunno what volvo call it but when an auto merc drops out of gear its time for a new gear cylinder.
Sorry guys, a little late in replying, but I have had the problem sorted.
It turned out to be the second gear cog and the engaging wheel worn.
Another £2000.
Just to top it off, my clutch servo went last week.
Another £1441 bill from Volvo.
I’m getting ■■■■■■ off now! 
hedas46:
Sorry guys, a little late in replying, but I have had the problem sorted.
It turned out to be the second gear cog and the engaging wheel worn.
Another £2000.
Just to top it off, my clutch servo went last week.
Another £1441 bill from Volvo.
I’m getting ■■■■■■ off now!
Come back ERF all is forgiven .
Nearly as bad as merc powershift.
Renewing second gear and dog clutch seems an odd solution to rectifying a problem with third and fourth gear.
Harry Monk:
I don’t wish to be the bearer of bad news, but it honestly sounds to me like the gearbox repairer has ripped you off and done a “Jizer and paint” recon.
I think Harry could have been right
cav551:
Renewing second gear and dog clutch seems an odd solution to rectifying a problem with third and fourth gear.
Because 3rd/4th on an ishift is 2nd lo/hi inside the box