Advice on gearbox

Hi everyone, I'm new to this board and the world of Land Rovers.
I've just bought a 2.25 L diesel LWB canvas back series 3. It was bought mainly to transport my trials bike, the odd trip to the dump and taking my kids out.On this basis it won't be doing many miles but I would still like it function properly.
It seems to jump out of 3rd gear as you coast up to a junction, the seller tells me its a weak spring that has ball bearing at the end of it. Does this sound like a likely cause ? and if so does the box have to come out to solve it.
While I'm here has any one got a series 3 manual they want to sell ?
Finally can anyone recomend a supplier of either an overdrive or a different transfer box as my series 3 sounds like its going to explode by about 45 MPH.

Cheers,
Tim

Hi TJM and welcome to Landyzone. I must admit i'm not big on the old gearbox info, but there are plenty of others here that are willing to help, and worry not we will try our best...

Hi TJL Good luck with your gearbox problem, has for your manual try this site or the links from it. www.ozedeph.com/links/manuals If not there just trawl the net there's loads of series stuff out there. Good luck

Hi TJM,
What trials bike do you ride?
Check out my site - one on landies, on on my old Cota, at:-
Teflon's Torque
TwinShockTrials
'box problem could be a detent spring, lack of detent spring cap or just a loose retaining plate.
Could also be worn syncro cones, worn detent plunger or worn selector forks.
Start at the top and work down!
After you get a manual.
Check the LROi forum; Series Spares
For an O/D unit. If you see spotter about, try looking in his profile for his home page 'LandRoverHeaven' - he breaks old Landies as a hobby business, often has useful bits of kit on offer.
Other wise, welcome to the nut house, pull up a straight jacket and make yourself at home

Teflon,

Sorry I've not replied sooner.

At the moment I've got a '92 Beta zero that I picked up on E-bay for £800 which considering it's condition seems to be a good buy. It's got a bit of history to it namely ( according to the original receipt ) it came from a shop owned by the Lampkins and was a 'works' bike and not a standard production line model.

Unfortunately I'm not good enough to ride it into the back of the Series 111 without the aid of a ramp.

Tim.