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Stock Markets June 30, 2026 05:19 PM

Allison Transmission Added to S&P MidCap 400; Goodyear Shifts to S&P SmallCap 600

Index rebalancing ahead of July trading session follows scheduled bank acquisition that triggers seat changes

By Priya Menon
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Allison Transmission Holdings Inc. will be incorporated into the S&P MidCap 400 index, while Goodyear Tire & Rubber Co. will exit the MidCap gauge to join the S&P SmallCap 600. The moves take effect before trading opens on July 6 and are tied to a pending acquisition that reassigns a slot in the small-cap index.

Allison Transmission Added to S&P MidCap 400; Goodyear Shifts to S&P SmallCap 600
GT PB MID ALSN SPCY
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Key Points

  • Allison Transmission will be added to the S&P MidCap 400 effective before trading opens on July 6.
  • Goodyear Tire & Rubber will move from the S&P MidCap 400 to the S&P SmallCap 600 on the same effective date, taking the slot associated with Stellar Bancorp.
  • The reallocation is linked to Prosperity Bancshares' acquisition of Stellar Bancorp, which is scheduled to close on July 1; sectors affected include industrials, consumer discretionary, and financials.

Allison Transmission Holdings Inc. is set to join the S&P MidCap 400, with the change scheduled to take effect before trading begins on July 6. At the same time, Goodyear Tire & Rubber Co. will be removed from the S&P MidCap 400 and will enter the S&P SmallCap 600, with the index transfers effective on the same date.

The seat vacated by Goodyear in the MidCap 400 will be filled by Allison Transmission. Goodyear's move to the SmallCap 600 will effectively replace Stellar Bancorp Inc., which is the company currently occupying that position.

The reallocation follows a corporate transaction in which Prosperity Bancshares Inc., a constituent of the S&P MidCap 400, is acquiring Stellar Bancorp. That acquisition is scheduled to close on July 1, a development cited in connection with the index adjustments.

Industry classifications for the companies involved are noted as follows: Allison Transmission is classified within the industrials sector; Goodyear Tire & Rubber is categorized under consumer discretionary; and Stellar Bancorp is listed in the financials sector. The article's timeline identifies the acquisition closing date of July 1 and the effective date for the index changes as before trading opens on July 6.

This piece reports the announced index reconstitutions and the corporate transaction that precipitates the slot swaps. It does not provide additional commentary on market reactions or trading implications beyond the effective dates and sector classifications stated above.

Summary of the changes

  • Allison Transmission will join the S&P MidCap 400 effective before trading on July 6.
  • Goodyear Tire & Rubber will leave the S&P MidCap 400 and enter the S&P SmallCap 600 effective the same date.
  • Stellar Bancorp's position in the SmallCap 600 is being vacated as Prosperity Bancshares, a MidCap 400 member, acquires Stellar in a transaction scheduled to close on July 1.

The article sticks to the announced index changes, the scheduled closing date for the acquisition, and the sector classifications provided for each company.

Risks

  • The index changes are tied to the acquisition of Stellar Bancorp by Prosperity Bancshares, which is scheduled to close on July 1 - if that transaction does not close as scheduled the planned seat adjustments could be affected.
  • The article does not provide information on market or trading impacts resulting from these index moves, leaving uncertainty about practical effects on liquidity or flows for the companies involved.
  • Timing sensitivity: the effectiveness of the reassignments is specified as before trading begins on July 6, so any change in schedule could alter the planned index compositions.

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