Eventually, the market's huge rally will turn from a tailwind into a headwind, Jim Cramer cautioned his Mad Money viewers Wednesday. There are plenty of things to be worried about, Cramer said, as he listed off his top 10 concerns.

First up were the banks, which need a strong employment number this Friday to keep interest rate hikes on track. Without strong employment data, Bank of America (BAC) - Get Report and JPMorgan Chase (JPM) - Get Report could be vulnerable. Next, the rails, a group of stocks that have gotten ahead of themselves, given there's not yet any appreciable pickup in cargo.

The third concern, the semiconductors, with rumors of flash RAM prices rolling over. Cramer also had concerns with Johnson & Johnson (JNJ) - Get Report and 3M (MMM) - Get Report , both of which received downgrades ahead of earnings.

Cramer was worried about aerospace, with Boeing (BA) - Get Report and United Technologies both trading at lofty multiples that will be hard to justify. So, too, with Starbucks (SBUX) - Get Report , an Action Alerts PLUS holding that Cramer was forced to trim recently.

Add to the list FANG, Cramer's high-growth tech cohort, and the chemical stocks like Dow DuPont (DWDP) - Get Report . Still others that have run into earnings are Caterpillar (CAT) - Get Report and Cummins (CMI) - Get Report . Cramer urged caution there as well.

Rounding out the list of concerns was IBM (IBM) - Get Report , a company that needs to begin its transformation this quarter or investors will head for the exits. Cramer also cautioned against the oil stocks and the cloud computing names, like Workday (WDAY) - Get Report and ServiceNOW (NOW) - Get Report , which are also ripe for a pullback.

Bill Ackman and ADP 

In a special interview, Cramer sat down with activist investor Bill Ackman, founder and CEO of Pershing Square Capital, for an update in his proxy battle with Automatic Data Processing (ADP) - Get Report . Viewers may recall that Cramer also interviewed ADP's CEO, Carlos Rodriguez, on Aug. 21.

Ackman said that activism is all about aligning boards of directors with shareholder interests. He said too often boards become complacent after the founder steps down and boards rarely own much stock themselves after that.

As for ADP, Ackman said that it is a terrific company with a long history, but over the past few years, it's been underperforming against its peers and should be doing a lot better. He said rivals like Paychex (PAYX) - Get Report , the CEO of which Cramer interviewed on Tuesday's show, are putting up much better gross margins than ADP and 25% of Paychex is a direct competitor with ADP.

Cramer and the AAP team have updates on a few names in their portfolio. Find out what they're telling their investment club members about Pepsico (PEP) - Get Report and Broadcom (AVGO) - Get Report and get in on the conversation with a free trial subscription to Action Alerts PLUS.

No-Huddle Offense

In his "No-Huddle Offense" segment, Cramer again sounded off against Equifax (EFX) - Get Report , as the company's CEO testified before Congress regarding its massive data breach.

Cramer said it's clear that company executives had material, non-public information as of the end of June, but CEO Richard Smith did not close the window on insider selling, and allowed executives to dump thousands of shares ahead of the public disclosure.

Cramer called this activity simply frightening and said the case should be immediately taken up by the SEC and the Justice Department. He said there's no way these executives could have thought the loss of 143 million Social Security numbers was not material information, and closing the insider window is standard operating procedure for any reputable company.

Over on Real Money, Cramer says Equifax should have slammed that selling window shut. Get his insights with a free trial subscription to Real Money.

Tyson Foods 

Sometimes, a great house in a bad neighborhood can surprise you, Cramer reminded viewers. That's certainly been the case with Tyson Foods (TSN) - Get Report , a stock that's popped 20% in just the past three months, after plummeting 30% late last year.

Cramer said that Tyson has gone from zero to hero this year, yet the stock still trades at a very cheap 13 times earnings.

The problem with Tyson came in late-2016, when the company was implicated in a poultry price-fixing scheme. Those suits are continuing, Cramer said, but are much less relevant than they were last year as the company has changed itself in big ways with excellent execution.

In February, Tyson announced new initiatives, including a new leadership team, a goal of using only antibiotic-free chicken and a renewed focus on healthy and humanely treated animals. This things all matter to younger consumers, Cramer explained, and the results are already paying off. Tyson also spent $3.2 billion to acquire AdvancePierre, a packaged foods maker with exposure to the growing convenience store market.

With a new image and strong earnings over the past few quarters, Cramer said the allegations of price-fixing no longer seem to matter and Tyson is clearly back from the dead.

DexCom Drops 

What the heck happened to shares of medical device maker DexCom (DXCM) - Get Report , the glucose monitoring provider that saw its shares plunge over 30% last week? Cramer said rival Abbott Labs (ABT) - Get Report received FDA approval for a competing product, which sent analysts heading for the hills.

Cramer issued a mea culpa for not taking the Abbott threat more seriously and recommending DexCom at its pre-plunge levels. "I underestimated the risk," Cramer explained, but that doesn't mean that DexCom is down and out for good.

As is the case with many technologies, DexCom was king of the hill before the Abbott news, but now finds itself with a rival that requires fewer finger pricks and costs less. In the best-case scenario, DexCom will to only have to increase its promotional activities to maintain its market share, but that will still cut into its gross margins.

DexCom does have a next-generation product set to debut later this year, however, and that product is shaping up to be more accurate than the Abbott product. Investors should also remember that DexCom is the only company to have received Medicare reimbursement so far, and that's a big deal.

In the end, shares of DexCom will rebound, Cramer concluded, but it may take some time to do so, which is little solace for those who owned shares last week.

Lightning Round

In the Lightning Round, Cramer was bullish on Seattle Genetics (SGEN) - Get Report , Benchmark Electronics (BHE) - Get Report and AT&T (T) - Get Report .

Cramer was bearish on Teva Pharmaceuticals (TEVA) - Get Report , Walgreens Boots Alliance (WBA) - Get Report and Snap (SNAP) - Get Report

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At the time of publication, Cramer's Action Alerts PLUS had a position in PEP, AVGO, SBUX, DWDP, ABT.