8-98025313-0 SPRING; RETURN,SHIFT FORK ISUZU for NPR75/4HK1

Precision Positioning for Shift Fork Return

The shift fork return spring provides the necessary force to return the shift fork and selector mechanism to a neutral or default position after a gear change . Isuzu Genuine Springs are manufactured to exact OEM free length and spring rate specifications, ensuring consistent shift feel and positive detent action, which is essential for preventing vague engagement or gear pop-out . Aftermarket springs with incorrect tension characteristics can cause difficulty in gear selection or incomplete return to neutral .

 High‑Grade Spring Steel for Fatigue Resistance

Shift fork return springs endure continuous compression and release cycles, sliding friction, and sustained exposure to transmission oil and heat . Isuzu Genuine Springs are formed from high‑grade spring steel, precision‑coiled and heat‑treated to achieve optimal tensile strength and fatigue resistance . For applications such as the F‑Series commercial truck, the standard detent spring length is 37.8 mm (1.488 in.), with a minimum service length of 34 mm (1.3385 in.) . This robust construction, available in genuine part number variants such as 8-98025314-0 (4KH1/NKR77)  and 1-09585053-1 (6HK1/FVR34) , maintains consistent spring tension over thousands of shift cycles, eliminating the loss of shift quality common with generic aftermarket springs .