Dongfeng Fengxing S50EV Drive Unit Assembly Removal and Installation Guide

Fault Background

The drive unit assembly of the Dongfeng Fengxing S50EV (1468 manual) is mounted on the subframe system's mounts: the splash shield is installed below, and the motor controller, on-board charger, high-voltage distribution box, air conditioning compressor, engine compartment trim cover, and corresponding accessories are assembled above in sequence — therefore, removing and installing the drive unit is essentially a "linked removal and installation of multiple engine compartment systems." The manual clearly states three iron rules: the drive unit as an assembly must not be internally disassembled (disassembly of drive unit related components is prohibited during repair); before removal and installation, remove the key + disconnect the traction battery service disconnect switch (MSD) + disconnect the 12V battery negative ground cable, and ensure the drive unit and motor controller are reliably grounded; the lubricant specification is unified ATF type 1.7L, with the drain/fill plug tightening torque at 47±5N·m and thread sealant (Loctite) applied. This article is organized as a removal and installation work guide.

Precautions and Preparations

1. Read the relevant instructions before removal and installation and wear personal protective equipment;
2. Without permission, do not open or reassemble the drive unit, do not replace with a drive unit from another manufacturer/model, and do not replace parts of the original drive unit;
3. During removal and installation, remove the key, disconnect the MSD and the 12V battery negative ground cable;
4. Before repair, ensure the drive unit and motor controller are reliably grounded;
5. During repair, it is prohibited to disassemble or decompose components of the drive unit assembly;
6. It is strictly forbidden for repair personnel to directly touch the high-voltage parts of the system with their hands.

Tools: Megohmmeter (to check drive unit insulation resistance), multimeter (to check wiring harness resistance), insulating gloves (for high-voltage connector removal and installation), lifting equipment.

Removal Procedure (9 Steps)

1. Pre-removal preparation: Drain the drive unit coolant completely (to prevent leakage during removal from contaminating the work area); open the drain plug (1) to drain the lubricant completely, then tighten the drain plug into the housing — torque 47±5N·m; apply a layer of Loctite to the plug threads before each retightening to ensure sealing;
2. Open the front hood and secure it with the support rod, remove the engine compartment trim cover (1);
3. Unplug one by one the high/low-voltage wiring harnesses connected to the high-voltage distribution box, on-board charger, motor controller, and drive unit — the 3-phase wiring harness (1) connecting the drive unit and motor controller is temporarily not removed; insulating gloves must be worn when removing wiring harnesses;
4. Disconnect the water hoses (2) connected to the on-board charger inlet/outlet nozzles (1) and the drive unit outlet nozzle, and disconnect the piping (3) connected to the air conditioning compressor;
5. Raise the vehicle with a lift to a suitable height — operators must wear safety helmets, and non-operators must not enter the work area; remove the splash shield (1) below the drive unit, and remove the front wheels and front brake discs (2);
6. Place a height-adjustable workbench flatbed cart under the subframe, adjust the height to support the subframe assembly, remove the fastening bolts, and slowly lower the flatbed cart to remove the subframe assembly from the engine compartment and transfer it to the assembly work area — if any component interferes with the assembly removal, remove the interfering component first to avoid damaging other components during lowering;
7. Separately remove the high-voltage distribution box (1), on-board charger (2), air conditioning compressor (3), 3-phase wiring harness (4), coolant hoses (5), motor controller (6), left and right half shafts (7), and their accessories from the subframe assembly — when removing the motor controller, the drive unit breather tube fixed to its housing must be pulled out; the 3-phase wiring harness cannot be removed from the drive unit before the mount bracket is removed;
8. Remove the 3 mounting point nuts securing the mount bracket to the subframe, and use lifting equipment to transfer the drive unit assembly to another work area;
9. Remove the 3 mount brackets and the 3-phase wiring harness from the drive unit.

Installation Procedure

1. Install each component in the reverse order of removal; the tightening torque for each component's fastening bolts/nuts refer to the corresponding system's service manual;
2. Complete the lubricant filling before assembling the drive unit assembly into the engine compartment: fill with unified ATF type lubricant 1.7L, and after filling, tighten the fill plug — torque 47±5N·m (keep the fill plug surface clean when removing; apply Loctite to the threads before retightening if not a new part);
3. After the vehicle is fitted with a new drive unit assembly, the motor controller must update the initial position angle information of the new drive unit into the software program (refer to Chapter 9 of the Motor Controller Service Manual) to ensure proper matching control of the motor system.

Common Fault Quick Reference

Safety Warnings

• This article is for technical reference. Drive unit removal and installation is high-voltage/heavy component work, must be performed by professionally trained personnel, with insulating gloves throughout, and it is strictly forbidden to directly touch high-voltage parts with hands.
• Three prerequisites: remove the key, disconnect the MSD, disconnect the 12V negative ground cable; ensure the drive unit and motor controller are reliably grounded.
• During lifting operations, wear safety helmets, non-operators leave the work area; lower the subframe slowly and remove interfering components first; check that lifting equipment is secure before lifting and transferring.
• The drain/fill plug threads must be coated with Loctite, torque 47±5N·m; after replacing with a new drive unit, initial position angle update is mandatory.

Repair Insights

The core of S50EV drive unit removal and installation is the "assembly mindset": the manual repeatedly emphasizes that the drive unit is not to be internally disassembled, not to be replaced with parts from other manufacturers, and repair means "separation from the vehicle" — this treats the drive unit as a black box, and the removal path becomes "strip the engine compartment peripherals (trim cover → wiring harnesses → water hoses → compressor piping → subframe → distribution box/OBC/compressor/half shafts) → remove the 3 mount points → lift away". Three easily overlooked details: the 3-phase wiring harness must "follow along" twice — not removed at the engine compartment stage, removed at the subframe stage, and cannot be removed from the drive unit before the mount bracket is removed; if the order is wrong, either the harness will be pulled and damaged or removal will be impossible; drain the oil before lifting — after the drive unit is off the vehicle, the drain plug is hard to access, and 47±5N·m + Loctite is the key to preventing oil leaks; after replacing with a new drive unit, the motor controller initial position angle must be updated — this is the other half of the same thing as MCU initial angle flashing, and if missed, resolver/position-related faults will be reported. Finally, remember the first row of the troubleshooting table: "Fault alarm cannot run → temporary stop, wait for motor to recover" — first wait for the protection to exit, then determine if it is a real fault.

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【This article is for reference only】