Like Jprovence and JIMBO said, the ZF 8-speed itself is a sweet rock solid transmission. The ones I’ve driven shifted very nice and solid without a whole lot of noticeable hunting like the GM 6L90’s do. ZF has always been known to be a top shelf high precision supplier of gear boxes, hydraulic pumps, etc. to the manufacturing world. We use a lot of ZF products on the vehicles my company builds where issues are practically unheard of.
After doing quite a bit of research in to the 8HP45 (Chrysler 845RE) over the past few weeks and found what posted back in 2013 in post 9 is not accurate as there wasn’t much information available when it first came out as to exactly how it worked. I mentioned the transmission used an Encoder motor on the side of the trans to shift the range selector shaft like how the electric 4x4 transfercases work. As it turns out, that is not the case. The 8 speed is truly fully electronic where it doesn’t have a mechanical range selector shaft with a mechanical park pawl like pretty much every other automatic in the world. The 8-speed park pawl is still throws a mechanical pin in a cog but it is spring loaded and electric actuated without any true mechanical linkage to the actual shifter. The lack of a truly mechanical linkage from the shifter to the safety devise (park pawl) is one major shortcoming of design of these 8 speeds in my opinion with potentially risky consequences as we are seeing take place now with FCA’s recent NHTSA investigations, lawsuits and recalls.
Many are quick to blame the user for these roll-aways and to certain degree that may be true, but there should be safety checks and balances in place to prevent issues if the operator doesn’t use the dial properly. To blame the driver for not using the Park Brake is ludicrous. The reality is most people do not use the park brake in automatic transmission equipped vehicles. I know I don't. Despite the questionable design of the ZF park pawls I’m also of the opinion there should be a FMVSS regulation to standardize the PRNDL operation instead off all these goofy dials, buttons and oddball shifters that Chrysler, BMW, Mercedes, Audi, Range Rover and so many are starting to use. When the manufacturers changed the operation of the transmission range shifting process some people have a hard time changing their subconscious routine from what they have known all their driving life. For that reason, Chrysler should have more safety checks and balances engineered into the system or better yet…use the same method of a truly mechanical linkage/cable operated park pawl like the industry has used for over 60 years.
Again, back in 2014 Chrysler voluntarily recalled a whopping 159 RAM 8 speed trucks for a problem with the park pawl pin where it wasn’t engaging which would cause roll aways. Given that they already acknowledged a previous issue (without placing blame on the driver) sure makes one wonder if the issue from 2014 wasn’t much broader than they first though or if there is an inherent design defect in that transmission. I feel it is all of above including some driver error but driver error alone shouldn’t be excuse. Then in April of 2015 they had to recall the Chrysler 200 with the same design for the same issue where the electronic park rod would bind also resulting in roll aways. No matter how you look at it, I feel there is a huge safety issue with the design of these ZF transmissions related to the park pawl operation. ZF is a great supplier but they are not perfect either and Chrysler has not done a good job of adding check and balances into the integration of the ZF park pawl design into their vehicles. Given Chrysler’s recent trend of roll away issues (200 ZF transaxle pins, 159 trucks in 2014, recent Jeep monostable shifter that killed the actor as well as other manufactures that use the ZF transmissions) and now this new investigation I would hate to be the compliance engineer at FCA and ZF trying to talk their way out of this mess with NHTSA. FCA cannot deny the RAM 8 speed roll away complaints started surfacing literally right after they hit the road. A media outlet commented on a potential issue back in a test truck before the launch but I can't remember which media outlet it was now.
BTW, I am not bashing on Chrysler or ZF. I am a huge Chrysler fan although I don’t own one at the moment but if I had a pile of money I would have a Power Wagon or AEV RAM in an instant.
