BMW Transfer Case Service

BMW Transfer Case Service

The transfer case is a rather unique design in the way that it operates a clutch pack mechanically, not hydraulically.

A customer who had a 2007 BMW X3 was having an erratic problem with the check engine light coming on and an issue with the transfer case 4W operation. The AWD vehicle had a 3.0L engine and 6L45 transmission with 65,000 miles on it.

The Bimmer was driven with a scanner to see what was up. In addition to an inconsistent AWD, the check engine light would reappear each time that it was cleared, indicating something more than just software. There were three different trouble codes that would set, which were manufacturer codes: 2A32, 2A37 and an eccentric 2A45.

  • Code 2A32 (P1014) refers to an eccentric sensor issue
  • Code 2A37 (P1017) also refers to an eccentric sensor issue
  • Code 2A45 (P103A) refers to an actuator motor malfunction

The transfer case is a rather unique design in the way that it operates a clutch pack mechanically, not hydraulically, somewhat like a GM. It’s called an Active Torque Control transfer case, and there are several models based upon the vehicle. The E83 requires an ATC 400, E53 an ATC 500 and the E70 requires an ATC 700. The differences have to do with capacity and hookup. (Figure 1).

Figure 1

Although there were several different issues, the main item responsible for all of it was the actuator motor that is bolted to the side of the transfer case. Once the actuator motor was removed, the motor’s drive gear was found to be partially stripped. The worm gear that contacts the motor drive gear appeared to be in good shape. In addition, the electrical part of the motor including sensors, etc. seemed to function well.

The reason that the actuator motor drive gear was only partially stripped is due to how it operates. When 4WD is called for, at whatever stage, the actuator motor turns the worm gear, which in turn applies the internal clutch pack providing the necessary slippage in 4WD, (Figure 2). The only movement of the actuator motor drive gear is enough to accommodate clutch pack clearance. The gear may strip only 25-30% of the teeth, meaning to take the cheap way out, rotate the gear 180°.

Figure 2

The traditional way to effect repair would be to purchase a new gear; however, the gear is not available from BMW. Only the entire actuator motor assembly is available from BMW, and it’s not cheap (it’s almost a grand).

The upside is a new gear is available in the aftermarket from the company Odometer Gears (odometergears.com) and it’s less than $100. The gear fits 2004-2010 models, (Figure 3). Log on to the website to view a video concerning gear replacement. When servicing this transfer case, make sure to use the proper fluid TF0870 (part number 83 22 0397 244) to avoid apply issues.

Figure 3

Inexpensive fixes do exist, although they can be few and far between.

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