The Jatco CVT used in the Dodge Caliber, Jeep Patriot, and Jeep Compass
Chrysler’s first use of a continuously variable transmission (CVT) was on the Dodge Caliber, the first of three similar cars, all of which used the CVT. The early version was criticized and a reprogrammed version, dubbed CVT2, replaced it.
CVT2 had more precise ratio control, and an AutoStick® feature providing manual control with the simulation of six stepped gears. Chrysler claimed the CVT2 brought 6%-8% higher gas mileage than a traditional 4-speed automatic.
The CVT transmission uses two V-pulleys and a steel push belt to vary the input to output speed ratio. The transmission engages the torque converter clutch almost immediately when accelerating, and keeps engaged throughout speed changes, eliminating slippage and increasing efficiency.
Optimized gear ratios, especially in the 30-60 mph range, improve passing and feel more responsive. Continuously varying the transmission ratio allows the engine to stay in its most efficient operating range.
CVT drivers should note that unlike an automatic transmission, there is no part-throttle downshift. To get full acceleration you press the gas down more. The engine will not change rpm as you accelerate so don't be fooled by the sounds - you are accelerating!
Jatco, which makes the CVT, is owned by Nissan and Mitsubishi, and many Nissans use the same basic transmission. Some past JATCO transmissions had been problematic, but the issues were apparently overcome before Chrysler started using them. Chrysler used their own unique electronics with these transmissions.
Dodge Caliber used an electronically controlled all-wheel-drive system with variable torque output, using the CVT as a central component. An electronically controlled coupling managed torque split from front to rear, driving only the front wheels until power to the rear wheels was needed, for better fuel economy. All-wheel drive was also used between 25 and 65 mph for precise handling during performance driving.
In 2010 models, the CVT was given “tip start” and a moderate gas-mileage boost.
Why AutoStick was added
“Having stepped ratios like a conventional transaxle goes against the original purpose of the CVT, but it comforts people who expect a downshift or upshift to occur because of lifelong conditioning to conventional shifting in steps.
The CVT chooses the optimum ratio for the speed, load and throttle position at a given instant. As it s-l-i-d-e-s up through its infinite ratios, it can have the disturbing sensation of a slipping clutch because that is what we are conditioned for, although it's working perfectly and as designed. Software tweaks in 2007 further refined the “feel” for the ratio change.
When DAF pioneered the CVT back many years ago, it was with a ~30 hp engine. There was no software back then. It was mechanical. It was viewed as the transmission of the future.
Ford left CVT development and went to 6-speeds after a couple of years (2006) because of the “feel” and software that they couldn't remedy. I believe that Chrysler's/JATCO's software is close to optimum.
There is no internal transaxle “brake,” the abrupt deceleration that some feel is in the engine/throttle control software. There are no service plans that I'm aware of to change this.
Pat added: “One reason for including Auto-stick with a CVT is for driver control. This allows for a fixed ratio to lower the ratio for hill descent, or pick a higher starting ratio for moving from a stop under slippery conditions like ice or snow.”
Even before AutoStick was added, a “low gear” mode was included.
Four wheel drive CVT
The Freedom Drive II Off-Road Package, when added to the Jeep Patriot, allowed it to be certified Trail Rated. The package included a continuously variable transaxle with a low range (CVT2L) that engaged when the off-road mode is activated; it had a best-in-class 19:1 low ratio, ideal for crawling over obstacles.
Origins of the CVT in Dodge and Jeep cars
Stas Peterson wrote in March 2010:
Chrysler chose the CVT from Jatco as a relatively last minute choice, when the Chrysler 6-speed dual clutch transmission was not coming along as planned. There is nothing wrong with that CVT, except that it has a fairly small overall gear ratio, between 4-5; other transmissions can have overall ratios between 4-7, so a smaller engine can have its power amplified by a wide overall ratio transmission. With the fine fuel economy at final drive ratios, and heavy amplification of the lightly powered, but fuel efficient, engine for acceleration needs in "lower gears," it would be a fine combination.
To make the World Engines sprightly they need(ed) a wider overall gear ratio, and the CVT couldn't deliver that. So the cars came across as noisy, thrashing, machines with little performance. That hurt sales. The (Fiat) dual clutch DCT 635 will cure that problem, as will the arrival of improved WGE engines featuring direct injection, Multiair, and turbocharging.
Jatco has developed a wide ratio CVT with a wide and fixed final gear ratio, in a size suitable for micro-cars; you have to expect similar changes to its entire CVT line. The new Jatco CVTs will offer an overall gear ratio of just over 7:1., instead of the present 4:1.