Pete Luban, the technical supervisor for ATSG, took the initiative several years ago to implement a safety protocol procedure for those who would call in for hybrid help. This was done for good reason, as this type of car could seriously injure if not kill someone if proper safety procedures are not known and followed. And those who were calling in had very little or no training at all in this regard.
Now, as a result of Luban’s efforts, when we receive a call for hybrid assistance, we fax a release form to be signed before we provide any tech support. The release form includes essential safety precautions such as the proper type of meter, meter leads and gloves needed to check high voltage (HV) wires as well as having an insulated pull off pole readily available. This release form also states that formal hybrid training should be sought out and attended.
With reference to repairing automatic transmissions in hybrid vehicles, I think that with time, we might see shops shake out into several categories. The first being shops who are resolved to never working on hybrids at all. The second will be those who will learn to safely work on the vehicle, so as to remove and overhaul transmissions that are not tied in with the HV system, as well as to perform various fluids and filter services. The third category will learn to safely diagnose and repair the HV systems including HV transmissions.
After a hybrid seminar I recently presented, I received many positive comments due to clarifying basic differences of transmissions used in hybrid vehicles. This clarification helped many become better oriented to hybrid work as it relates to transmissions.
Honda hybrids, for example, use a typical CVT transmission, which can be removed and worked on in the same way as if it were in a conventional gas powered vehicle. This CVT transmission is not used in the HV voltage system. It is the HV IMA (Integrated Motor Assist) system and gas engine that sits in front of the transmission which is used to input torque into the transmission, nothing more. This type of hybrid is often times referred to as a mild hybrid. Another example similar to this is the BMW ActiveHybrid 7 vehicle. It uses a ZF8HP automatic transmission behind a gas engine and electric motor like the Honda. This ZF8HP transmission still continues to use a hydraulic torque converter with a lock-up clutch. Once removed from the vehicle it’s a typical ZF automatic transmission sitting on your bench.
The next style hybrid transmission is a system that uses both clutch pack assemblies and motor generators internally. This means three phase HV wires from an inverter go to and enter the transmission for the motors located inside the transmission. GM’s two-mode front wheel and rear wheel drive transmissions as examples of this type of arrangement.
The technology that went into designing this type of transmission was a joint effort that included Daimler, Chrysler and BMW. If my facts are right, this alliance was established in 2005 and ended around 2009. This is in part why you will find this style transmission in GM vehicles as well as BMW and Mercedes. This is a fully automatic variable speed transmission having the ability to shift through gears like a conventional transmission and go into a CVT type ratio change.
The last example of a type of hybrid transmission to mention is used in Toyota and Ford vehicles. Both manufacturers refer to their transmissions as an eCVT type. These transmissions contain electrical motors and a power splitter gear set. There are no clutch pack assemblies inside these transmissions only the electrical motors and gearing to produce variable speeds.
It was this personal observation that I shared that several of the seminar attendees said they really enjoyed. For after I made these clarifications, I then had a platform from which I could further elaborate what a shop would need to know and do to repair, rebuild or replace a hybrid transmission. The highlights of this portion of the seminar can be read in an article I wrote inside this second edition of POWERTRAIN PRO called “Hybrid Transmission Diagnostic and Repair.”
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