Despite slower automotive sales and continuing pressure to reduce prices, supplier earnings continue to increase in the first three months of 1995 over year-ago figures. Most credit lean manufacturing and operating systems for the growing margins. Some examples: Allied Signal Automotive ups its first-quarter net from $52 million in 1994 to $56 million this year.Seating Corp.'s profit goes from $6.5 million in '94 to $17 million in '95, while competing Johnson Controls Inc. gains 27% to $32.3 million in the period. ITT Automotive increases its earnings 60% over the same period last year, and Inc.'s automotive group celebrates an 82.8% profit improvement over 1994 with $172.9 million in earnings. Rockwell Automotive improves from $656 million in '94 to $815 million in '95; Trinova Corp.'s $22.6 million is its best quarter in six years; Arvin Industries Inc. improves from $479.2 million in '94 to $553.4 million in '95; Walbro Corp.'s net is up 19.5% versus a year ago; Timken Co. reports record first-quarter earnings of $34.3 million, up from $7.7 million in '94, and Textron Inc. boasts a 14% increase in profits to $109 million.