Probably the most difficult job which I've had on a 504/505 is undoing the nut on top of the strut, if the strut shaft has a flat screw driver slot and if the nyloc in the nut is very tight (can be particularly bad if you have Gabriel inserts).

The solution I've found is to burn out the nyloc with the oxy torch (taking care not to burn the rubber at the top of the strut -not easy -make sure you have a watering can handy).

I now burn the nyloc out on new nuts before I assemble them and use loctite instead. I also use the Aliquant strut inserts which have an Allen key hex in the top. This makes the job so much easier to disassemble next time. Also it's a good idea to put grease or never sieze/copper coat on the shaft where it passes through the rubber mount, because these can sometimes rust together making disassembly impossible, unless you destroy the rubber mount.


[edit]Added "Peugeot" to topic heading. Thanks for contrib Dave