Front should always be bigger than rear or same size. Post some photo's of brakes with drums off

I have a spare in Jarrow will check it out are they handed as would need to know whether near or off side. Edit the oil filler hole shows which side is which.

Trying to find a decent or repairable 2.25 engine [petrol preferably] Birmingham area if possible. For a lady owner see attached LR uk post https://www.lrukforums.com/threads/dirtyberties-engine-thread.263263/page-80#post-1752411

If both ends of rad are hot i would suspect rad blocked and only partly working temp should reduce from top to bottom. Take the grill off and feel the whole width of rad to see if all even temp or buy an infared temp gauge to check it. Is the fan slipping ie belt tight enough.

Check the gearstick grub screw drivers side of the alloy housing the ball sits in.[goes in a slot in gear lever ball and if loose allows ball to move out of alignment] The only spring on the gear lever itself is in base of the alloy housing.

I think Burlen will rebush it for you. http://burlen.co.uk/

In the front transfer case i.s a dog clutch which engages front wheel drive when selected as Rob says above. Free wheel hubs where an after market option to reduce noise and supposedly reduce fuel costs.

The defender 200tdi manual shows washers fitted which look similiar to what you have

Who did you buy the sliding glass seal from , bought one from Blanchards and had same issue ended up putting the worn out old one back on. Bought some different rubber from Woolies trim but that also did not fit.

Check the selector shafts at front of transfer case they corrode and need cleaning / releasing. See attached info.

How is a broom shank supposed to pass the sun gear shaft in centre of diff ? See attached pic with a halfshaft in place.

Had you pushed yellow knob down to engage 4wd high ratio? If so the selector shafts in transfer case may be seized which would explain why you are snapping halfshafts if your off roading with 2 wd. I made a bracket to attach to trolley jack to allow me to remove diff on my own from underneath...

It is worth taking the cover off the ends of high low selector shafts and oiling them up whilst you have the floor up. Check the tin cover as they tend to rust through.

These snips from series 2 manual show its location.

I have some spare instruments and noticed awhile ago that there was two different threads on the clamp stalks depending if early or late type unit.

Copper grease is an anti seize product ideal for bolts that are going to be left a longtime before being undone again. Colliery shaft men used to use it on cage winding gear which was exposed mineral loaded water . Had a tub from pit which is now used up the replacement copper grease I bought...

I have an old fashioned impact driver that you hit with a hammer works well. Like this https://www.ebay.co.uk/itm/Hand-held-impact-driver/284186657966?hash=item422ad844ae:g:eVUAAOSwUstgK~mM

When you look at the drum with wheel off should be 1 or 3 countersunk screws around the centre area of hub flange and a threaded empty hole take the three screws out and screw one into the threaded hole . Replacement drums only have 1 screw originals 3 screws.

Are you using the countersunk screw from the drum in the threaded hole to get it started?

Success definetely faulty and cannot even blame Britpart rubber quatlity hope your new one is a good quality as it looks awkward to get at.