I see that a little clarification is needed.
Das Boot Page 312,

'Glory be to God on high!' intoned TGM Hacker. 'More room at
last,' he added for my benefit. He wiped his sweaty neck with a grubby
piece of towelling and urged his coolies on. 'Come on, lads, bear a hand
on that tackle.'
'Nothing like Vaseline for an easy ride!' Ario hauled on the chain in
time to Hacker's cries of 'Heave!' - which he punctuated with ex-
clamations of his own. '@!#$ me - @!#$ me, you randy sod - ooh, ooh,
ooh! - that's it - and again!'
I wondered where he found the breath, toiling as hard as he did.
Merker, who was also hauling grimly on the chain, pretended to be deaf.
With the first torpedo safely in its tube, Merker planted his legs apart
and mopped the sweat off his chest, then passed the grimy rag to Ario.
Stimulated by obscene banter, my own imagination took wing. The
iron hymen of a ship's side ruptured by the torpedo-phallus, the jagged
labia, the freighter-cow rearing as the torpedo pierced her vitals and
ejaculated its fiery semen, the ripping and rending, writhing and
groaning . . .
The first lieutenant came forward to check the pistons. The men
continued to labour, doggedly. There was nothing to be heard but
smothered curses and the rhythmical cries of the torpedo gunner's
mate.

Possibly they removed the grease for storage and re-greased the torpedo just before firing. A little grease substantially reduces the frictional forces.