HOUSTON -- What a finish.

Aramis Ramirez belted his ninth career grand slam and Marlon Byrd drove in three runs to back Carlos Zambrano and spark the Cubs to an 8-3 victory Saturday over the Astros.

Chicago improved to 24-12 under interim manager Mike Quade, who may want to start thinking about how to decorate the manager's office at Wrigley Field. He probably won't look that far ahead.

"The main thing ... when I came in here, [we hoped] we would finish with energy and we could continue, especially the kids, to get better and the veterans would continue to play," Quade said. "All of that took place and resulted in a real nice record and a lot of wins.

"Without that kind of effort and that kind of progress from those guys, you guys might be writing a whole different story," he said. "I'm looking forward to the final day and taking some time off."

Zambrano closed the season 8-0 with a 1.41 ERA in 11 starts since coming back from the restricted list. It's been quite a roller coaster ride this season as Zambrano (11-6) has gone from Opening Day starter to the restricted list for his dugout tantrum to being unbeaten in 11 outings.

"If you lose a tick or two off your fastball from six years ago when you're a youngster, OK, how are you going to get people out now?" Quade said. "He's still got great movement, his split was excellent tonight and he used it effectively, his slider continued to be a decent pitch.

"Maybe he's figuring some stuff out as far as pitching," Quade said. "Since he's come back, I know [pitching coach Larry Rothschild] spends a ton of time with him, and whatever adjustments he's made mentally and physically allowed him to have a great finish."

The question now is, can Zambrano take what he did the final six weeks of the 2010 campaign and do it for six months next season?

"That can be said about the whole group and all of us," Quade said. "We'll see."

The right-hander held the Astros to two hits over six scoreless innings, but in the seventh, Hunter Pence was safe on an error by third baseman Bobby Scales, who had replaced Ramirez at third. Zambrano walked the next two batters to load the bases before a run scored on a fielder's choice by Chris Johnson. Brett Wallace followed with a two-run double and Zambrano was lifted.

He obviously wasn't happy when he handed Quade the ball, but Zambrano said it was because he was unable to reach a goal of 130 innings. Zambrano finished with 129 2/3 innings.

"When he handed me the ball, he was mad, and I'm OK with that," Quade said. "I wish after the mistake [by Scales] he was able to get some people out, and he didn't. You know when you go to get the ball from him that he's not going to be happy coming out and he's not going to be happy about what's taken place."

The new Zambrano, who has undergone anger management therapy, was able to laugh after the game.

"I'm enjoying the game," he said. "I'm enjoying every moment, every situation of the game and being happy every moment. That's the key to being successful."

The key in these final 11 starts has been more movement on his pitches as opposed to velocity.

"He's been doing it for a while and he's got good stuff, and his biggest thing is he keeps you off-balance," said the Astros' Brett Wallace. "He's got multiple pitches, his split, his slider and his heater that he can locate when he really needs to. He went out there and pitched well and kept us off-balance, and that's what happened."

J.A. Happ (6-4) took the loss, giving up eight runs on eight hits and five walks over three-plus innings. Byrd hit a run-scoring groundout in the first and Alfonso Soriano added an RBI double, his 40th, to put the Cubs ahead, 2-0. Byrd hit a two-run single in the second.

In the fourth, Chicago loaded the bases, taking advantage of an error by third baseman Chris Johnson. Ramirez then crushed his first slam of the season off a 1-0 pitch to give the Cubs an 8-0 advantage.

Ramirez has now reached 25 homers for the sixth time with the Cubs and is one of six players to have six or more 25-homer seasons with the team. The list includes Sammy Sosa (12 times), Billy Williams (10), Ernie Banks (10), Ron Santo (eight) and Ryne Sandberg (eight).

Since Quade took over, the Cubs are 17-4 on the road, trailing only the Phillies for the best mark in that stretch. He will become the fifth Cubs manager to post a .600 or better winning percentage as a mid-season replcement. Whitey Lockman went 39-26 (.600) in 1972 after replacing Leo Durocher.

The Cubs are 19-9 in September with one game remaining, and assured of posting their first winning month of the season. It's the first time in 117 years that the team will have a winning record in the final month after sub .500 marks in every other month.

So, will Zambrano be the Cubs' Opening Day starter in 2011?

"The rotation is [Ryan] Dempster [on Sunday] and I'll see you guys next year -- maybe," Quade said. "It's a long winter. We're all day-to-day."

What does Zambrano think?

"I don't know -- talk to 'Q,'" he said, then smiled. "Talk to 'Q.'"