I recently did this job to my Defender 90 TD5. There are two difficult aspects of this job, removing the seating inside the draglink and refitting the base plate against the spring pressure and inserting the circlip. I had done the job before on my 90 V8, but the drag link was on the bench then as I had replaced the steering box.. This time I was in a hurry and needed to do the job with the drag link still attached to the vehicle. I'll assume you already removed the old parts.

I removed the inner seating by finding a socket which just went through the top ring (which the rubber boot attaches to) but which engaged on the top of the inner seating, which is a smaller diameter. I then got a 'G' clamp with one end on the top of the socket and the other end on a small piece of steel plate across the hole underneath the drop arm. Tightening the clamp removed the seating quite easily. The new one was difficult to insert - but after cleaning up the hole it tapped in eventually, again using a socket and a hammer.

After assembling the new parts in their correct order, I found it was extremely difficult, if not impossible, to push the base plate into the draglink against the pressure of the spring enough to secure the circlip, and an ordinary 'G' clamp kept sliding off and didn't leave room to get the circlip in. Going through my shop looking for ideas, I saw an old caulking (mastic in UK) gun hanging up. For anyone not familiar with this, it looks like a tubular frame into which a tube of caulking is fitted and a trigger which when worked pushes a plunger through the centre of the frame. It occurred to me that this could be used as a sort of clamp, as you can now buy clamps which work on the same principle. The circular end of the gun fitted well over the top of the ball joint (see photo) - the threaded part of it projecting through the circular end - and, using a 3/8" socket extension or an extension socket (as in photo) between the plunger and the base plate, I worked the trigger and the plunger pushed up the base plate against the spring and held it tight - hands free! - enabling me to use both hands to squeeze the circlip into its groove! It worked just great. (The photo was taken underneath a friends old, rusty Range Rover, but it was the same drop arm as a 90.) Also, I find sockets very useful as tools apart from their obvious use. When putting in a new clutch, a tapered socket of the right size works great as a clutch plate centralizer and support for the plate whilst you tighten the bolts on the cover. Push a socket extension bar through the clutch center to retrieve it.