LT77/R380 in a Lightweight?

I've just sold my 1971 series 2a lightweight to a local chap. He has delivered it to his mechanic already, to replace the petrol engine with a Disco 200tdi. He would like an accompanying modern gearbox in there also to replace the recon series 3 box I had put in last year. I don't think this is possible with the series axles on the Lightweight as there are not cv joints but u joints on them. Is this correct?

If so, could he do an axle transfer, from say, a Disco - to overcome a gearbox change situation? There are rocky mountain parabolics and dampers on all corners. I guess the added advantage would be discs instead of drums to slow down a much perkier drive with the 200tdi.

The buyer's alternative was an overdrive and these can be hard to find and hit or miss on a decent unit. I appreciate it's not my problem, now that it's sold, but the advice is useful to a new owner and I wish I had gotten more help when I bought my first Landy!

Any advice welcome.

Yup full time 4 wheel drive will destroy a series axle. Disco axles are wider than series ones too and it'd be a ****load of work to make em fit. An overdrive's the answer. You can get a brand spanker for about a grand which is probably cheaper than having a mechanic do all the other distasteful stuff you mentioned.,

Or get a manky old one and have it reconed.
Putting the 200 on the series box is a better idea.
That said ashcrofts do a kit for the r380 (ok not the lt77), whereby the diff lock shift lever becomes a diff lock / 2wheel 4wheel drive selector, more compatible with the landy front axle.
Never looked into it too hard, but I believe range rover front axles fit the series and have cv joints, anyone any comments?

I don't think it's worth the hastle or expense of fitting an LT77 gearbox to go with the Tdi engine. The UJs on the rear propshaft on an 88" Land Rover are very close to binding with the rear suspension fully extended. With the longer LT77 box the propshaft would have to be shortened which would mean that the prop would probably be running at exessively acute angles in certain situations, so ideally wide angle UJs might be needed. Mountings would have to be made for the gearbox, the transmission tunnel and floor would need to be altered and the front propshaft length would probably have to be changed. Then the diffs would need to be changed to 3.54:1 types otherwise the gearing would probably be lower than with the standard box! I personally dont think that running an LT77 gearbox with a standard series front axle would necessarily cause a problem though. How about fitting freewheeling hubs, and for road use dissengage them and lock the centre diff, so you get 2WD? Range Rover / Disco / Defender axles don't go onto series Land-Rovers very easily because the track rod fouls the leaf springs, then there is the problem of the axles being wider so you fit wheel arch extensions and then you might start wandering why you didn't just buy a Defender.

Series Land-Rovers go just fine with a series box in my experience. With just a bit of drilling and tapping, fitting of some extra studs and removing a couple of dowel pins, the engine just bolts on to the box no hassles.

Yep as above keep the series's box.
Has the mechanic in mention have any experience with landy's?

I ve got rangey axles (and coils) on my 1974 lightweight, so was also considering putting an LT77 in it but I came to the same conclusion as Fenby, that the already short rear prop would end up even shorter and may not work very well off road - wide angle uj's (double cardans or something i seem to remember) would be a must and i understand they are quite pricey.

That said, i believe it HAS been done before, so we just need that someone to step up and tell us how much pain is involved.....

All this of course is why the deffy doesnt have the bay window at the front like the rest of us.