Valve body repair JF402E JF405E (Daewoo Matiz / Kia Picanto)

JF402E / JF405E is a four-speed automatic transmission developed in 2000 by Jatco for small cars Daewoo, Kia and Suzuki (Japanese market only) with a transverse engine arrangement. In our market, it can be found on Daewoo Matiz and Kia Picanto paired with 0.8L and 1L engines.

Like all 4-speed automatic transmissions, the JF402E is structurally very simple and fully studied by repairers, but earlier in the field of automatic transmission repair there were no solutions for repairing valve bodies, in case of problems with it, the valve body was simply changed to a new or more "live" used version. Now everything is different, we have developed and launched into production a series of overhaul valves and tools for their installation, which will make it easy and simple to refurbish JF402E valve bodies.

You can diagnose a valve body malfunction by the following symptoms:

Slips in all gears
Power-on delay D or R
There is no self-starting in D or R mode when you take your foot off the brake, you need to additionally step on the gas

The reason for such symptoms is the upper plate of the valve body, namely the batteries located in it.

If the box overheats, there is no torque converter lockup, and computer diagnostics show error P0741 - the reason lies in the middle plate of the valve body, namely in the main pressure valve and the torque converter lockup valve.

Repair beginning - disassembling 

Valve body disassemble

We start the repair of batteries that are installed in the upper plate. Structurally, the accumulator consists of a valve body channel (acts as a sleeve) and a spring-loaded piston. The piston reacts to changes in oil pressure and moves inside the liner, while the spring acts as a damper to prevent sudden, abrupt pressure changes. The failure of the pressure accumulator is most often associated with the destruction of the valve surface as a result of exposure to contaminated hydraulic fluid - transmission oil. Oil contamination occurs mainly due to the destruction of clutches, while fragments and surface material of parts gets into the oil and causes abrasive wear of the valve bodies parts.

One of such units is the pressure accumulator. In case of malfunctioning of the battery, problems arise with the level of the working oil pressure in the valve body, as a result, the process of controlling the mechanical part of the automatic transmission is disrupted. As a result, there are shocks when shifting gears, slipping of the clutch drums, indistinct gear changes, and the absence of a torque converter lockup.

                                                                                                        The photo below shows a battery with a damaged anodized layer

The repair algorithm for the top plate is as follows:

• On a milling machine, the battery hole is bored to the size of the repair sleeve
• The repair sleeve is made and installed
• own production new accumulator isinstalled inside the sleeve, the coating is cold hard anodizing, resistant to wear.

This video shows the process of boring a hole in the body of the valve body, making a repair sleeve and installing it. The video is partially not relevant, now we use modern CNC machines for the manufacture of bushings, but the principle of repair has not changed.

New accumulators are installed

Vacuum testing and valve replacement in the middle plate

                                                                                             There are 2 modulator valves in the plate, we check the channel + valve pair for tightness, the indicators are low

We  install modulators which are 0,02 mm larger than standard ones  and we get such a vacuum, this is an excellent result.

We are testing the torque converter lock-up valve, it also needs to be replaced.

Lock up valve is replaced for oversized valve +0.02 mm, problem is solved

We check the Main Pressure Regulator valve, one of the most important in the valve body, since the quality and stability of gear shifting and the overall operation of the transmission depend on its correct operation

The vacuum readings are very low, in this case there is only one repair option, the installation of a repair valve. We produce and use ourselves at our service stations and also sell repair valves and reamers for JF402E:

• Oversized valve  Main Pressure Regulator Valve JF402E JF405E
• Reamer for installing Main Pressure Regulator Oversized Valve JF402E JF405E

We fix the plate on the slipway for fastening valvebodies plates and ream the channel:

We install a new valve

We managed to raise the tightness to the required level. That's all, the valve body can be assembled.

Such repair takes 1 working day and for valve body repair we give a 1 year warranty with no mileage limitation.

The parts and tools that we used for this repair can be viewed on the links below:

• Neutral Control Oversized Valve 09A JF506E | Clutch JF402E JF405E (size +0.015mm)
• Lockup Control  Oversized Valve (size +0.015)mm JF402E JF405E
• Main Pressure Regulator Oversized Valve JF402E JF405E
• Reamer for installing Main Pressure Regulator Oversized Valve JF402E JF405E
• Retainer for automatic transmission valve bodies repair 

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