BER Berkley W R Cp

Caterpillar Inc.'s (CAT) railcar products and services unit has agreed to buy diesel-electric locomotive maker Electro-Motive Diesel from private-equity firms Berkshire Partners LLC and Greenbriar Equity Group LLC for $820 million.

Electro-Motive Diesel's 2009 revenue totaled $1.8 billion. The deal is expected to close by the end of the year and comes as signs of life emerge for orders of new train cars. Tens of thousands of existing ones were idled last year during the recession.

Sliding demand for construction machines has weighed on Caterpillar's sales of late. The heavy machinery company swung to a sharply higher-than-expected profit in its latest quarter following prior-year restructuring charges, though revenue fell.

Caterpillar shares were down 1.1% at $45.50 in premarket trading as stock-index futures were down about the same amount.

-By Matt Jarzemsky; Dow Jones Newswires; 212-416-2240, matthew.jarzemsky@dowjones.com