M/T - Difficult Shifting Into 1st or 2nd Gears

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CATEGORY
Transmission


SECTION
4


PAGE
8


ISSUE
05/92-0206


CODE
471


Subject:
Difficult Shifting into 1st or 2nd gears

Application:
Early 1991 900 Models with Manual Transmission


Some early 1991 900 models may develop complaints for difficulty shifting into 1st or 2nd gears, especially if the driver shifts aggressively. Several changes have been made in the production of later transmissions to prevent these problems. Complaints may be expressed as "grinding into 2nd gear," or "hard to shift into/out of 1st gear."

The possible cause(s) and remedy of the complaints are as follows:

A. Chamfers on the inner surface of the splines on synchronizer muff 87 28 487 may be missing or inadequate. As the transmission is shifted into 2nd gear, the leading edges of the splines on the 2nd gear-side of the muff may be deformed inward to form burrs. As the muff is then slid over the 1-2 hub to engage 1st or 2nd gear, the burrs on the muff's splines may cause the muff to bind on the hub.





^ Remedy: Slide 1-2 muff manually over its hub. If it binds, inspect the splines on 2nd gear side of muff. If the chamfer on inner spline surface is missing or the ends do not come to a point, replace the muff (reuse the original hub). NOTE: Improved muffs were introduced as from gearbox serial number A14202-.


B. Poor molybdenum coating on the 2nd (and 3rd) gear synchronizer ring 87 28 461. The coating may not adhere properly to the brass ring so that it flakes off. The surface finish of the coating also may not be coarse enough to effectively brake the rotation of the gear, preventing smooth gear changes into 2nd especially when cold.





Remedy: Inspect the condition of the molybdenum coating on the 2nd and 3rd synchronizer rings. Rings on which the coating has flaked or worn off should be replaced. Rings containing improved coatings were introduced into production as from gearbox serial number A31280. They can be identified by markings located on the inside of the ring. Early rings are marked with 2 raised "dots." Later rings with improved molybdenum coatings have 3 marks, the 2 raised "dots" plus 1 "dimple." 2nd and 3rd gear synchronizer rings without the 3 marks should be replaced as needed.

Also inspect the condition of the engagement splines on the 2nd gear. Gears on which the points on the splines have been severely rounded over should be replaced as needed.


C. The groove for the locking clip used to secure the 1-2 selector fork to the 1-2/3-4 shift rail may have been insuffi ciently hardened. As a result, the groove can wear so that the 1-2 fork no longer fits tightly on the shaft. In some extreme cases, the locking clip may actually dislodge from the shift rail.


^ Remedy: Inspect the 1-2 shift fork and groove in the shift rail for its locking clip for wear. The clip should fit snugly on the rail so that the fork is held firmly in place. If the fork and/or shift rail are worn, replace the fork, shift rail and locking clip as needed.


As usual during gearbox repairs, all gaskets should be replaced, not reused for reassembly. Proper sealants also must be used between the case halves and on all required fasteners. See Service Manual 4:1 for details.

For best gear shift quality, use only 10W-30 or 10W-40 motor oil as the gearbox lubricant (mineral-based oils only).