Transfer case input shaft splines regeneration VOLVO, Hyundai, Kia , Mazda

In our practice of repairing and refitting automatic transmissions and transfer gearboxes, it is not uncommon to encounter the problem of wear or breakage of spline joints, both in the transmission and in transfer cases, power take-off shafts (PTO - Power Take Off), bevel gears and other variations of transfer cases.

The reasons can be very different:

• Driving style.

Aggressive driving, sudden starts from a standstill, off-road driving. Increased loads provoke premature wear of unit components.

• Overheat.

Extreme load increases friction between components by heating them. Elevated temperatures affect the physical characteristics of metals, which leads to possible deformation, the formation of gaps, which entails premature wear of connections and components.

• Routine maintenance (TO).

Failure to comply with maintenance regulations leads to wear and tear of dust and moisture-proof components that prevent the influence of the environment on the protected components.

If a worn or damaged oil seal or boot is not detected in a timely manner, it leads to direct penetration of dust and moisture into the spline joints, forming corrosion which leads to degradation of the metal and its gradual destruction.

How does a car behave with worn transfer case spline joints?

It all depends on the degree of wear of the splined coupling:

• Spline wear is less than 15%.

In the initial stages, as long as the gap between the splines remains within acceptable values, no significant changes in the dynamics of the car’s behavior are observed.

• Spline wear is 30-45%.

Significant wear of the spline connection, the connection does not form a rigid connection, free play is formed (play at the connection point). The car loses dynamics, shocks and impacts are felt when all-wheel drive is engaged.

• Spline wear is greater than > 60%.

Critical wear and gap between splines, threat of breakage of remaining splines. When the spline clutch rotates, the transmission of torque to the all-wheel drive differential stops. All-wheel drive is not possible.

In TF-80SC and TF-81SC transmissions, the splines wear out more often on the transfer case input shaft than on the differential. The connection between the input shaft of the transfer case and the differential is made through a splined coupling (2712-XC90D5RH FEBEST).

The connection point with the shaft is located on the outer part of the transmission and is more exposed to the external environment and, as a result, to corrosion.

Regeneration process:

1. A shaft with damaged splines is fixed in a lathe.
2. Damaged splines are cut off, and a seat is formed for a new spline bushing.
3. A splined sleeve made of hardened steel is pressed onto the shaft.
4. After pressing, the bushing is laser welded.
5. We get a transfer case shaft with regenerated splines.