Quite a lot about them on LR4X4 site.

Problems with expander can be, incorrect re assembly, or one of the little pistons [bottom] drops out unnoticed when replacing shoes, or it is just worn out.

Last year the original stat in my 200 gave up. I had two OEM replacements, one did not work at all and the other packed up after a month [stuck open] Found a new old stock original "Waxstat" been fine since.

Yes I get that,. The question remains why would the OP want to unless it is for a job like mentioned in my post above?

That was pretty much the system that was used 40 years ago. However nearly all air brake systems today use compression rather than the vacuum of old.

The plain answer is no, in good order in the UK they work well enough. What type/year is yours. Issues. Old matrix can get clogged, there may be some flow but not enough. The seal between the heater unit and cab may be crap, often the case when cold air getting into cab. Heater pipes themselves...

Did you when going over the hand brake parts do any work/clean of the expander?

There was at one time an air brake set that was available. This was for the Land Rover to tow air brake equipped trailers. A mate had an early Ninety with it fitted. We think it was for the ability to move empty trailer's around a site/dock. The landy's brakes were just the usual ones.

Why do you think transfer box oil is low? Been leaking?

And if you go laneing others will not think you are a newbi with them dents.

One other thing to do while it is out is to change the rear crank shaft seal. I recommend you use a Dowty type seal ERR2532 OEM along with a new gasket between block and flywheel housing. Follow book instructions with fitting the seal.

The front wing is a nut and bolt job to change but the rear TUB [as it is called] arch side is a fair old job.

No such thing as a "series one Defender" and never will be. Like asking a pack mule to be a show horse. PS would rather have the mule any day.

On a series 3 the fuse box under the steering wheel is notorious for poor connections.

No idea what size but it will be imperial.

Diesels can get hot in the combustion chamber area very quickly.

Kits are available to overhaul those older lift pumps who's sections are held together with screws.

The bonnet pin that drops into the hole between bolts in pic above can not be released/removed while bonnet is shut. Follow instructions above, Get some lube in there. Sometimes when the lever has been moved over and still does not release bonnet a hard slap of the hand on the bonnet will...

On a series you could lock up all four wheels on the adjusters. Handy cross axle escape when off roading with two opposite wheels off or nearly off the ground Lock one spinning in the air and send drive to wheel on the ground. Often when stuck you only have to move a couple of feet to get free...

Here is a story from long ago. In 1983 when the first 110 coil sprung Land Rovers came on the market Land Rover decided to have a 2x4 system option available thinking that many byers would be coming from having Series Land Rovers that had the more usual 2 wheel drive for the road and four wheel...