Dav Whatmore's men faced the south coast side hoping to continue their Championship rival with a third successive win.
Gallian, himself looking for a return to form after his hand fracture, is still trying to sort out his future by negotiating with the club for a better deal - and if those talks break down, Sussex would be leading the chase for his signature.
Lancashire were boosted by the return of captain Mike Watkinson, who took the field for his first Championship match in a month after shrugging off his long-term shoulder injury.
There were comebacks too, for Test stars Mike Atherton and John Crawley, but fast bowler Glen Chapple missed out again with his abdominal strain.
Coach Whatmore said: ``We've had a week off and I think it's done us all good. ``We needed the rest and the time to look at what's gone wrong and what's gone right recently. Hopefully, we will be able to slip straight back into the same kind of form which brought us two Championship victories.''
That lifted the club from the basement to 13th, and another maximum points win over struggling Sussex could see the Red Rose club in the top five.
Sussex, three from the bottom of the table, had to make a late decision on bowlers Paul Jarvis or Vasbert Drakes.
Lancashire were put into bat and move on to 20 without loss off 6.2 overs.
* Burnley youngster Kamran Farooq was called in to the squad for Lancashire's second team game against Essex starting at Chelmsford today.
Captain Peter Sleep said: ``Kamran bowled reasonably well in the nets for us yesterday and we're looking to give him a chance in the next couple of weeks.''
But Farooq was expected to be left out of the eleven with his county debut put on hold.
* Lancashire's Andrew Flintoff will captain the England under 19s side at Hove on August 1 and Southampton on August 4 in the limited overs internationals against Zimbabwe before three Tests glater in the month. Former Lancashire captain John Abrahams will manage the side.