Allison Transmission Holdings Set to Join S&P MidCap 400 and Goodyear Tire & Rubber to Join S&P SmallCap 600

Rhea-AI Summary

Goodyear Tire & Rubber (NASD: GT) will move from the S&P MidCap 400 to the S&P SmallCap 600 effective before trading on July 6, 2026. Allison Transmission will join the MidCap 400, and Stellar Bancorp will be removed from the SmallCap 600 following its acquisition by Prosperity Bancshares.

Positive

• GT added to S&P SmallCap 600 effective July 6, 2026

Negative

• GT removed from S&P MidCap 400 effective July 6, 2026

Market Context

This announcement transitions STEL out of the S&P SmallCap 600 as its acquisition by Prosperity Banc...

Analysis

This announcement transitions STEL out of the S&P SmallCap 600 as its acquisition by Prosperity Bancshares approaches, framing the stock more as a merger-arbitrage situation. Low short interest helps contain volatility, but closing execution remains important.

Key Figures

Effective index date: July 6, 2026 Expected deal close: July 1, 2026 S&P MidCap 400: 400 +3 more

6 metrics

Effective index date July 6, 2026 Index changes for STEL, ALSN and GT become effective before market open.

Expected deal close July 1, 2026 Prosperity Bancshares acquisition of Stellar Bancorp expected to close.

S&P MidCap 400 400 Index in which Prosperity Bancshares is a constituent before the changes.

S&P SmallCap 600 600 Index that Stellar Bancorp is leaving as Goodyear replaces it.

S&P 500 500 Flagship S&P index cited among S&P DJI benchmarks.

First index year 1884 Year Charles Dow created the first index referenced by S&P DJI.

Historical Context

5 past events · Latest: May 20 (Neutral)

Pattern 5 events

Date	Event	Sentiment	24h Move	Catalyst
May 20	Dividend declaration	Neutral	-0.0%	Quarterly cash dividend of $0.15 per share announced for June payment.
Apr 28	Earnings results	Neutral	-0.7%	Q1 2026 results and merger progress update with closing expected around July 1.
Apr 22	Merger approvals	Positive	+0.1%	All required regulatory approvals received for pending Prosperity acquisition.
Jan 28	Earnings results	Neutral	+11.6%	Q4 and full-year 2025 results with capital actions and merger disclosure.
Jan 28	Acquisition announcement	Positive	+11.6%	Prosperity agrees to acquire Stellar in cash-and-stock merger valued near $2.0B.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Pattern Detected

Recent STEL news has more often aligned with positive price reactions than diverged, though responses to routine items can be mixed.

Key Terms

s&p midcap 400, s&p smallcap 600, s&p dow jones indices, gics sector, +1 more

5 terms

s&p midcap 400 financial

"Allison Transmission Holdings Inc. (NYSE: ALSN) will replace Goodyear Tire & Rubber Co. (NASD: GT) in the S&P MidCap 400"

The S&P MidCap 400 is a group of 400 companies that are smaller than the big, well-known corporations but larger than tiny startups. It helps investors see how medium-sized companies are performing in the stock market, acting like a barometer for this middle-sized group of businesses.

s&p smallcap 600 financial

"Goodyear Tire & Rubber will replace Stellar Bancorp Inc. (NYSE: STEL) in the S&P SmallCap 600"

A stock market index made up of 600 small-cap U.S. companies chosen to represent the performance of smaller publicly traded firms. It matters to investors because it acts like a temperature gauge for the small-company segment of the market, serving as a benchmark for fund managers, a basis for index funds and ETFs, and a way to compare returns and risk when building a diversified portfolio.

s&p dow jones indices financial

"ABOUT S&P DOW JONES INDICESS&P Dow Jones Indices is the largest global resource"

S&P Dow Jones Indices is the organization that creates and maintains widely used stock market benchmarks, such as broad market and sector indexes. Think of it as the scorekeeper that measures how groups of stocks are performing; investors and fund managers use these benchmarks to compare results, build passive funds and ETFs, and gauge overall market health, so index changes can affect investment flows and portfolio strategies.

gics sector financial

"Effective Date | Index Name | Action | Company Name | Ticker | GICS Sector"

GICS sector is one of the major industry groupings from the Global Industry Classification Standard, a system that sorts companies into consistent categories (like Technology or Health Care) based on the primary business they do. Investors use these sectors like folders in a filing cabinet to compare companies, build diversified portfolios, and track how whole parts of the market are performing rather than focusing on single stocks.

dow jones industrial average financial

"such as the S&P 500® and the Dow Jones Industrial Average®."

A stock market index that tracks the share prices of a small group of large, well-known companies to give a quick snapshot of how the broader market is doing. Think of it like a thermometer for the stock market: it uses a handful of heavyweight firms as representative samples to show whether investor sentiment is rising or falling, which helps investors gauge market trends and compare performance over time.

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AI-generated analysis. How Rhea-AI works. Not financial advice.

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NEW YORK, June 30, 2026 /PRNewswire/ -- Allison Transmission Holdings Inc. (NYSE: ALSN) will replace Goodyear Tire & Rubber Co. (NASD: GT) in the S&P MidCap 400, and Goodyear Tire & Rubber will replace Stellar Bancorp Inc. (NYSE: STEL) in the S&P SmallCap 600 effective prior to the opening of trading on Monday, July 6. S&P MidCap 400 constituent Prosperity Bancshares Inc. (NYSE: PB) is acquiring Stellar Bancorp in a deal expected to close July 1.

Following is a summary of the changes that will take place prior to the open of trading on the effective date:

Effective Date	Index Name		Action	Company Name	Ticker	GICS Sector
July 6, 2026	S&P MidCap 400	Addition		Allison Transmission	ALSN	Industrials
July 6, 2026	S&P MidCap 400	Deletion		Goodyear Tire & Rubber	GT	Consumer Discretionary
July 6, 2026	S&P SmallCap 600	Addition		Goodyear Tire & Rubber	GT	Consumer Discretionary
July 6, 2026	S&P SmallCap 600	Deletion		Stellar Bancorp	STEL	Financials

ABOUT S&P DOW JONES INDICES

S&P Dow Jones Indices is the largest global resource for essential index-based concepts, data and research, and home to iconic financial market indicators, such as the S&P 500® and the Dow Jones Industrial Average®. More assets are invested in products based on our indices than products based on indices from any other provider in the world. Since Charles Dow invented the first index in 1884, S&P DJI has been innovating and developing indices across the spectrum of asset classes helping to define the way investors measure and trade the markets.

S&P Dow Jones Indices is a division of S&P Global (NYSE: SPGI), which provides essential intelligence for individuals, companies, and governments to make decisions with confidence. For more information, visit www.spglobal.com/spdji/en/. 

FOR MORE INFORMATION:

S&P Dow Jones Indices
index_services@spglobal.com

Media Inquiries
spdji.comms@spglobal.com

View original content:https://www.prnewswire.com/news-releases/allison-transmission-holdings-set-to-join-sp-midcap-400-and-goodyear-tire--rubber-to-join-sp-smallcap-600-302815143.html

SOURCE S&P Dow Jones Indices

FAQ

When will Goodyear Tire & Rubber (GT) join the S&P SmallCap 600 index?

Goodyear Tire & Rubber (GT) will join the S&P SmallCap 600 before the market opens on July 6, 2026. According to S&P Dow Jones Indices, this follows index changes linked to the Stellar Bancorp acquisition.

Why is Goodyear Tire & Rubber (GT) leaving the S&P MidCap 400?

GT is leaving the S&P MidCap 400 as part of scheduled index changes tied to the Stellar Bancorp acquisition by Prosperity Bancshares. According to S&P Dow Jones Indices, Allison Transmission will take GT’s place in the MidCap 400.

Which companies are being added to and removed from S&P indices on July 6, 2026?

On July 6, 2026, Allison Transmission joins the S&P MidCap 400 and GT joins the S&P SmallCap 600. According to S&P Dow Jones Indices, GT and Stellar Bancorp are being removed from the MidCap 400 and SmallCap 600, respectively.

How is the Stellar Bancorp (STEL) acquisition affecting S&P index membership?

Prosperity Bancshares’ acquisition of Stellar Bancorp is prompting index adjustments effective July 6, 2026. According to S&P Dow Jones Indices, Stellar Bancorp will be deleted from the S&P SmallCap 600, while GT moves into that index and Allison Transmission joins the MidCap 400.

What happens to Goodyear Tire & Rubber’s (GT) sector classification after the index change?

GT remains classified in the Consumer Discretionary sector after moving to the S&P SmallCap 600. According to S&P Dow Jones Indices, only its index membership changes on July 6, 2026, not its Global Industry Classification Standard (GICS) sector.