Michigan continued to rebound from its mediocre 1984 season with its second straight victory over a Top 20 opponent, defeating 15th-ranked South Carolina, 34-3, yesterday in Columbia, S.C., behind the passing and running of Jim Harbaugh.

The senior quarterback capped a time-consuming 76-yard drive by scoring on a five-yard run late in the first period and pitched out to tailback Jamie Morris for a four-yard touchdown run that gave the 19th-ranked Wolverines a 14-0 lead with 2:11 left in the first half.

Harbaugh, who completed seven of 17 passes for 74 yards in last week's victory over Notre Dame, which knocked the Irish out of the Top 20, finished 12 for 22 for 164 yards.

Harbaugh completed three third-down passes on Michigan's first touchdown drive, including a 41-yarder to Paul Jokisch, his 6-foot-8 split end.

Mike Gillette added field goals of 39 and 30 yards in the second half. An eight-yard run by Gerald White and six-yard run by Thomas Wilcher in the fourth quarter capped the scoring for the Wolverines, who had 507 yards total offense -- 324 rushing and 183 passing.

The Michigan defense held South Carolina's veer attack to 33 yards in the first 27 1/2 minutes. Backup quarterback Allen Mitchell, who replaced Mike Hold in the second period, directed a no-huddle drive that covered 75 yards in 2:10 and Scott Hagler kicked a 22-yard field goal with one second left in the half for South Carolina's only points.

"We had them outweighed by a big margin," said Michigan Coach Bo Schembechler, "and we thought we could wear them down, especially after we saw how breezy and nice the weather was to play in (85 degrees with a 10-mph wind). When we were on offense, we had a decided weight advantage up front."

Michigan, which will play Maryland Saturday in Ann Arbor, Mich., is 2-0 after finishing 6-6 last year, its first non-winning season since 1967. South Carolina, which had defeated The Citadel and Appalachian State, both Division I-AA teams, is 2-1.