TM 10-3930-659-20 7-12. TRANSMISSION THERMAL BYPASS VALVE PRESSURE TEST (Con't). PRESSURE TEST 1. Remove hose (1) and preformed packing (2) from transmission oil sampling valve (9).  Discard preformed packing. 2. Install preformed packing (21) and plug (5) in hose (1). 3. Install preformed packing (8), union (7), adapter (6), hose (4), and pressure gage (3) on transmission oil sampling valve (9). 4. Remove plug (17) and preformed packing (18) from tee (19).  Discard preformed packing. 5. Install two preformed packings (10 and 16) on adapter (11), and install adapter, union (15), adapter (14), hose (13), and pressure gage (12) on tee (19). 6. Warm hydraulic system fluid to operating temperature (see paragraph 2-29) and observe readings on two pressure gages (3 and 12).  Readings on pressure gages must start out low and increase as hydraulic system fluid Is warmed and transmission thermal bypass valve (20) opens. 7. Shift transmission to N (Neutral) and run engine at fast engine idle speed (see TM 10-3930-659-10).  If reading on two pressure gages (3 and 12) is 31-39 psi (214-269 kPa), replace transmission thermal bypass valve (20) (see paragraph 7-13). 8. Shut down engine (see TM 10-3930-659-10). 9. Remove pressure gage (12), hose (13), adapter (14), union (15), and adapter (11) from tee (19). 10. Remove two preformed packings (10 and 16) from adapter (11).  Discard preformed packings. 11. Install new preformed packing (18) and plug (17) on tee (19). 12. Remove pressure gage (3), hose (4), adapter (6), union (7), and preformed packing (8) from transmission oil sampling valve (9).  Discard preformed packing. 13. Remove plug (5) and preformed packing (20) from hose (1).  Discard preformed packing. 14. Install new preformed packing (2) and hose (1) on transmission oil sampling valve (9). 7-36