Lower rear shock mount nut
 

Any one know what size the nut is on the lower rear shock mounts?? I seem to have lost mine!!

Model year probably matters (you might want to add that info). If it is 97+ it is a M12 x 1.75 nut. (at least that is what the Omix-ADA replacement nut for 97+ XJ specifies.

I looked it up in my '00 and '84 to '86 parts catalogs and they both indicate what jordan96xj said. M12 X 1.75. Looks like there is a washer too.
So do yourself a favor. Read this:

https://www.cherokeeforum.com/f2/research-249236/

Thanks! M12x1.75 is what worked.