"We got some big hits from Dunn and Griffey," Reds interim manager Jerry Narron said. "Griff's big three-run homer was huge for us at the time of the ballgame. ... I like the way we played."
Griffey's homer, his 24th, capped a four-run rally in the sixth. It was his 18th in 61 games since May 25. He also doubled.
Dunn's shot in the third was his 33rd and tied him for second in the NL with Chicago's Derrek Lee. It was Dunn's 10th homer in 24 games since the All-Star break. He went 2-for-5 and has 27 hits in his last 83 at-bats.
"Hey man, a 9-spot," Claussen said his offensive support. "That's like getting 5-under par on the back nine rolling up 18. The only thing I was disappointed with is that I did walk some guys."
The left-hander has won his last three starts after dropping four straight decisions.
"He's had some tough luck against these guys, so it's good to see him come out and pitch the way he did," Kearns said. "Any time you can do that here against a lineup that can hit the ball out of the ballpark like them, that's impressive."
The Cubs fell to 27-27 at Wrigley Field and are 6½ games behind Houston in the NL wild-card race. At 54-58, Chicago is in fourth place in the NL Central, four games ahead of fifth-place Cincinnati.
"We're just in a funk and we can't seem to find a way out of it," said Walker, who had three of Chicago's nine hits. "The last inning, we bust out of it and hopefully that will carry over."
Chicago starter Jerome Williams (3-5) allowed seven runs on seven hits and two walks in 5 1/3 innings. The right-hander is 0-3 in three starts at Wrigley Field since being acquired from San Francisco on May 28.
Cubs starters have posted only two wins since July 19, a span of 19 games.
"We couldn't get the ball down today," Cubs manager Dusty Baker said. "The ball was up and the location wasn't where he wanted it. Power hitters -- when you get the ball up and over the heart of the plate, you're going to get hurt."
Valentin's bases-loaded double in the second gave Cincinnati a 2-0 lead. Dunn's homer, a line shot to right-center in the third, extended the lead to 4-0.
Kearns led off the sixth with his homer, and Griffey connected with two outs in the inning to make it 8-0.
Valentin drove in Cincinnati's final run with a groundout in the seventh.
- While the middle of the Reds' lineup is hitting, the top isn't. Ryan Freel and Felipe Lopez, the Reds' leadoff and No. 2 hitters, are hitless in their last 41 at-bats combined. On Monday, Lopez was in the leadoff spot and went 0-for-3 with two walks and a run scored. Freel batted second and was 0-for-5.
- Cubs SS Nomar Garciaparra played his first game at Wrigley Field since April 13. He tore a groin muscle in St. Louis on April 20 and returned from the DL last Friday in New York.
- The Cubs' longest losing streak this season is eight games.
- Monday was the 17th anniversary of the Cubs' first night game, on Aug. 8, 1988. That game started, but was rained out.