Transmission Disassembly Inspection

Disassemble the transmission per the procedure outlined in the appropriate Service Manual.

When disassembling the NP 2500 manual transmission the following items must be inspected to ensure you have correctly diagnosed and repaired the transmission.


^ Check the detent spring and bullets for wear or damage.

^ Check to see that the reverse blocker spring is in the proper position (long end forward).

^ Remove the shift fork pins as outlined in the Service Manual. Do not drive the pins through the shift rails. Driving the pins through the shift rail will bend the rail. Bent shift rails will cause high shift effort.

^ Check the shift rail interlock plates for wear or damage.

^ Check fork pads for wear and shift rails for fit and free movement.

^ Before disassembling the main shaft check for proper assembly of the gears, synchronizer assemblies, snap rings, and thrust washers.

^ Check snap rings, thrust washers, anti-spin pins, and retaining ring for wear or damage.

Figure 1:

^ Measure the individual synchronizer stop ring clearance. Minimum stop ring clearance is .025 inch (.6 mm), Figure 1. When the clearance is less then .025 inch the synchronizer assembly must be replaced.

Figure 2:

^ Check the stop ring threads. Threads should be relatively sharp with only a small land surface on the top of the threads and should be consistent around the inner circumference of the stop ring, Figure 2. The synchronizer assembly must be replaced if the threads are worn unevenly.
^ Inspect all bearings for wear and roughness. The races, balls, and rollers must be free of chipping, pitting, flaking, brinelling and etching. The bearing must not bind on the shaft or fit loosely in their bore.

^ Inspect the gear tooth contact pattern. The contact pattern should be centered on the tooth and have a width of approximately 75% of the tooth. A tooth contact pattern which is too low, too high or localized in the front or back of the tooth may be contributing to gear noise.

NOTE: DURING THE GEAR MANUFACTURING SMALL IMPERFECTIONS SUCH AS PITS, NICKS, BURRS OR CHIPS ARE REMOVED BY A GRINDER. THE SMALL GRINDING MARKS LEFT BY THIS PROCESS ARE LOCALIZED AND SHOULD NOT BE CONSIDERED AS A SOURCE OF GEAR NOISE.


^ Measure the counter shaft end play (.001 to.005 inch)