Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

The best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Transamerica Large Cap Value I2 (TWQZX): 0.63% expense ratio and 0.59% management fee. TWQZX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. TWQZX has achieved five-year annual returns of an astounding 12.72%.

Invesco Energy Investor (FSTEX Quick QuoteFSTEX - Free Report) : 1.25% expense ratio and 0.73% management fee. FSTEX is classified as a Sector - Energy mutual fund. Throughout the massive global energy sector, these funds hold a wide range of quickly changing and vitally important industries. With yearly returns of 18.94% over the last five years, FSTEX is an effectively diversified fund with a long reputation of solidly positive performance.

Nuveen Quant SMid-Cap Eq R6 (TSMWX): 0.46% expense ratio and 0.42% management fee. TSMWX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. With a five-year annual return of 13.29%, this fund is a well-diversified fund with a long track record of success.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.