UPDATE 1-ArvinMeritor sells shock unit, stock gains

*ArvinMeritor sells third auto part business unit

*Private equity firm OpenGate Capital buying Gabriel unit (Adds detail, background, share price movement)

DETROIT, June 29 (Reuters) - ArvinMeritor Inc (ARM.N) on Monday said it had completed a deal to sell the U.S. operations of a unit that sells shock absorbers and struts, its third deal to sell parts of its unprofitable auto parts business in the past week.

Shares in ArvinMeritor closed up by almost 13 percent on Monday extending a rally that has seen the stock more than quadruple in value since early April.

ArvinMeritor said it completed the sale of the U.S. operations of Brentwood, Tennessee-based Gabriel North America to Los Angeles-based OpenGate Capital, a four-year-old private equity firm that also has operations in Paris. It said itexpects to complete the sale of a Mexican subsidiary of Gabriel within two months.

Terms of the transaction were not announced.

Last week, Troy, Michigan-based ArvinMeritor sold two other businesses selling parts such as shocks and springs that it had held in its light-vehicle chassis business.

Taken together, the three deals mean that ArvinMeritor has sold businesses representing about 72 percent of the sales of its chassis operations.

Barclays Capital analyst estimated that the Gabriel unit had about $200 million in revenue in 2008 and said the sale price would have reflected the depressed market for auto parts at a time when production has been slashed and U.S. auto sales are near 30 year lows.