BMW; ZF 6HP26

Transmission general data

This 6-speed automatic transmission was designed by ZF jointly with BMW. Since 2001 this transmission has been used for all high priced vehicles with rear-wheel drive and engines with the capacity of up to 6 litres. The list of brands using this transmission includes Bentley, Aston Martin and Maserati. Since 2006 this transmission has been used in Ford, Hyundai, Jaguar, Land Rover.The 6HP26A modification found application on FWD Audi and VW models. It has the torque capacity of up to 600Nm.This 1-st 6-speed automatic transmission from ZF triggered the start of production for next generations of this family - 6HP19 -21 intended for engines with lower torque (up to 420 Nm) and 6HP32 – for max torque (up to 750 Nm).

6HP26 Specs

The gearbox is controlled by a revolutionary for that time TCM (transmission control module) named the ZF 6HP Mechatronic / Mechatronik. The 6HP26 torque converter boasted an innovative lockup system with a peculiar mechanism, which facilitated lockup in all 6 gears. Multiple gear ratios in the ZF 6HP26 transmission were housed inside a small area, using a conventional planetary gearset and a gear assembly designed by P.Ravigneaux. Power transfer actions are covered by 5 clutch packs. At that, compared to its predecessor, the ZF 5HP, this 6-speed transmission used fewer parts and was lighter

6HP26 Typical problems, technical issues and repair guidelines

Typical problems for this transmission family includes: vibrations which lead to wear of bushings and drum Е resulting in problems with 4-5-6 gears shifting; issues with other speeds caused by wear of solenoids and torque converter lock-up result in problems with the pump and seal leakage, slippage of frictions (slow acceleration) which leads to overheating, burnt oil and necessity for automatic transmission reassembly with the use of repair kits.

6HP26 Mechatronic problems

The mechatronics unit is similar to the one used in 6HP19 and they have the same problems. There are two generations of valve bodies.VFS (Variable Force) solenoids frequently become the source of numerous issues. Intensive operation on cross-section in the environment of contaminated fluid and high temperature leads to premature wear and abnormal operation. Mechatronics in these ZF automatic transmissions are sensitive to static electricity, even when touching contacts with your hands.

6HP26 Mechatronic Seal Issues

Issue: a range of common 6HP26 transmission are frequently due to loss of pressure from the required level caused by the wear or failure of the small seal between the 6HP26 transmission mechatronic controller and the transmission case. If it fails, the following 6HP26 transmission problems will manifest themselves:

• Unexpected 6HP26 clutches failure,
• Transmission pump malfunction,
• Failure of the torque converter clutch.

Solution: replacement and reinstallation of the 6HP26 Mechatronic adapter seal.

6HP26 Pump problems

Worn pump bearing and pump stator are frequently replaced during maintenance services. Problems of both abovementioned parts are related to worn components of torque converters and related vibrations. Typical replacement operation of the first priority is related to the overheating and aging of the rubber: - Separator plate of the valve body, 6HP26/ 6HP19.Overdrive Е package with frictions, steel and thrust discs gets burned first from clutch packs. The same problem is typical for structurally similar 6HP19.The problem in winter time – replacement of the adapter to the solenoid assembly.

6HP26 Torque converter problems

The torque converter is a common problem for powerful vehicles equipped with this transmission. If repair specialists order bushings, then it means the torque converter repair as well.After the overhaul it is required to reset computer settings. This family of ZF6HP transmissions is in great demand in the repair business and at the same time is considered to be as repairable as its predecessor - 5HP19. The service life of this transmission can reach 1 “million” kilometers under the condition of timely and accurate overhaul of the transmission (as well as maintenance).

Excessive wear of the TC clutch in the 6HP26 torque converter due to active lockup triggered even at as low as 1st gear. Subsequently, drivers can experience the following problems:

• Delays in engaging the right gear,
• Slipping gears,
• Unpredictable up/down shifting,
• Excessive heating of the transmission,
• Unusual noises from the transmission.

Solution: key to remedying the ZF 6HP26 torque converter problems is installation of a new / replacement torque converter unit. Torque converter repair specialist might effectively use certain special tools helpful in the remanufacturing procedure. It is also important to remember to address replacement of the excessively worn transmission fluid and issues with cooling.

6HP26 Solenoid Issues

Issue: different gear ratios are controlled by 7 solenoids and if one of these 6HP26 solenoids becomes damaged or worn out, following problems arise:

• Delays in shifts,
• Sticking gears,
• Refusal to turn a gear,
• Slipping gears.

Solution: a serious number of common problems with 6HP26 transmission is due to valve body solenoids failures. The right approach to remedy this is replacement of the faulty 6HP26 solenoid. Solenoid testing equipment is recommended to identify the damaged one.

6HP26 E Clutch failure

Issue: wear out of the 6HP26 clutches, which are key in power transfer from one gear to the next. Friction material used in the clutches is important for grabbing. Improper maintenance or reckless driving will wear them out prematurely. The common 6HP26 clutch failure symptoms are as follows:

• Clutch slipping,
• Delays in shifts,
• Harsh shifts,
• Failure of gear engagement,
• Excessive heating.

Solution: rebuilding or replacement of the transmission unit corrects this common 6HP26 transmission issue.