The Dutchman has endured a mixed start to life at Old Trafford as United have already dropped 10 points this season.
David Moyes lasted less than a year in the job before being sacked, and Ferguson, who himself took three years before winning a trophy at the club, hopes that Van Gaal will be afforded more time.
"He's not been getting the results that are expected but when I came to the club I didn't get the results I expected myself at the beginning," he told MUTV.
"What we needed then was Sir Bobby Charlton, Martin Edwards and the board to stick by me and we had a great spell after that.
"Once I got settled into the club, everything was fine. Louis is going through that same process and there's no doubt in my mind that he will sort it out."
United, who sit fourth in the Premier League table, travel away to West Bromwich Albion next Monday following the two-week international break.