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

News Market Reaction – PB

+0.47%

+0.47% Session close to close

In the Jul 1 session, PB gained 0.47%, reflecting a mild positive market reaction.

Data tracked by StockTitan Argus on the day of publication.

Market Context

This announcement highlights index reshuffling driven by PB’s pending acquisition of Stellar Bancorp...

Analysis

This announcement highlights index reshuffling driven by PB’s pending acquisition of Stellar Bancorp effective around July 1. PB’s prior M&A and earnings updates have drawn mostly modest reactions; ongoing insider net selling and deal execution will remain key watchpoints.

Key Figures

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

6 metrics

Effective date July 6, 2026 Index changes effective prior to market open

Stellar deal close July 1 Prosperity Bancshares acquisition of Stellar Bancorp expected closing date

S&P MidCap 400 400 Index Allison Transmission will join; Goodyear exits

S&P SmallCap 600 600 Index Goodyear will join; Stellar Bancorp exits

S&P 500 500 Flagship S&P equity index referenced in company description

First index year 1884 Year Charles Dow created the first index cited in article

Historical Context

5 past events · Latest: Apr 29 (Neutral)

Pattern 5 events

Date	Event	Sentiment	24h Move	Catalyst
Apr 29	Earnings report	Neutral	-0.9%	Reported Q1 2026 earnings, merger impacts, balance sheet and margin details.
Apr 22	Dividend declaration	Positive	-0.2%	Announced Q2 2026 quarterly cash dividend and confirmed asset base size.
Apr 22	Acquisition approvals	Positive	+0.1%	Received required regulatory approvals for pending acquisition of Stellar Bancorp.
Apr 07	Earnings call invite	Neutral	+1.8%	Scheduled and detailed access for the upcoming Q1 2026 earnings call.
Feb 02	Merger completion	Positive	+1.5%	Completed merger with Southwest Bancshares, issuing new PB shares and integration plans.

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

Pattern Detected

PB has generally reacted in line with the tone of corporate updates, with mostly modest aligned moves and one divergence on a dividend announcement.

Key Terms

s&p midcap 400, s&p smallcap 600, s&p 500, dow jones industrial average, +1 more

5 terms

s&p midcap 400 financial

"July 6, 2026 | S&P MidCap 400 | Addition | Allison Transmission"

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

"July 6, 2026 | S&P SmallCap 600 | Addition | Goodyear Tire & Rubber"

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 500 financial

"home to iconic financial market indicators, such as the S&P 500® and the Dow"

The S&P 500 is a broad stock market index that tracks the performance of 500 large U.S. companies, weighted so bigger firms have a larger impact. Investors use it like a thermometer or benchmark to judge how the overall U.S. stock market or a portfolio is doing; movements in the index influence investor sentiment, fund performance, and many passive investment products that aim to match its returns.

View in glossary

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.

View in glossary

gics sector financial

"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.

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.