There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

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.

Wilshire Large Company Growth Investor (DTLGX) has a 1.3% expense ratio and 0.75% management fee. DTLGX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With yearly returns of 11.69% over the last five years, this fund clearly wins.

American Funds Investor Company of America F1 (AICFX Quick QuoteAICFX - Free Report) : 0.62% expense ratio and 0.23% management fee. AICFX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With yearly returns of 14.06% over the last five years, AICFX is an effectively diversified fund with a long reputation of solidly positive performance.

Transamerica Large Cap Value R6 (TALCX): 0.62% expense ratio and 0.59% management fee. TALCX 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. With a five-year annual return of 13.53%, 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.