This isn't form "before", but I thought it was worthy of being mentioned.
The biggest object in TARDIS that I remember from 2005 series is... a star, on a verge of collapse to a black hole.
It appears in the 11th Doctor episode Journey to the Centre of the TARDIS.
It's called the Eye of Harmony - a power device. The Doctor describes it thus:
DOCTOR: The Eye of Harmony. Exploding star in the act of becoming a black hole. Time Lord engineering. You rip the star from its orbit, suspend it in a permanent state of decay.
Transcript from Chakoteya
To append Valorum's point about tanks, a video from series 9, episode 1 - The Magician's Apprentice):