Munich, 16. October 2013 – chrysler is two months behind schedule with production of the jeep cherokee. Around 10.000 cars are waiting for completion. According to chrysler, this is due to the lengthy process of fine-tuning the transmission software for the transversely mounted nine-speed zf torque converter automatic. In the usa, sales were scheduled to start in july, in europe at the end of 2013.
As some european automotive media reported with reference to the detroit news and wall street journal chrysler is working on reprogramming the control system of the 9hp nine-speed automatic transmission from german supplier zf. Particularly in conjunction with the 2.4-liter, 184-horsepower gasoline engine, problems are said to be occurring with eighth and ninth gears. There is talk of overly jerky gear changes.
Electronics take over
We are not surprised, since zf did not provide these two gears with the usual multi-disc brake clutches, which can more or less gently wear down every shift due to friction. In order to save installation space, hydraulically operated claw clutches are used here, which can only be controlled with a control system that is really very well matched to the respective engine so that there is neither jerking nor cracking when shifting gears.
This solution, which is unique in series production vehicle construction, is a prime example of the takeover of power by electronics in drive technology. The difficulties confirm the age-old insight of off-road vehicle drivers that the technology in an off-roader must be as simple as possible.
With the new cherokee, chrysler has also radically changed its target group. Irony of fate: the jeep cherokee with all its high-tech is a great hope for chrysler. Group ceo sergio marchionne said in july that without a successful launch of the cherokee, chrysler could forget its goals for 2013.
It’s interesting that in the case of the cherokee it’s apparently not the transmission: in the land rover evoque, it already impresses with refined, almost imperceptible and fast gear changes.