I recently bought a 2008 Jeep Patriot (2.4/CVT2) with the ?Auto Stick? feature.
I understand you can shift from Drive to 6th gear at highway speeds and it drops the RPMs significantly! Indicating that it is really an additional overdrive to save gas!
I tried it and it really does drop the RPMs.
Any thoughts???
Sounds good, an overdrive gear should help your fuel mileage. Just be careful not to lug the engine at lower speeds, you may have to manually downshift (I don’t know how that system works).
If this is a six speed automatic transmission, when the gear selector is placed in “Drive” it should automatically shift into the highest gear (which is overdrive) when the vehicle reaches the appropriate speed. Can you explain the function of this transmission?
This is a CVT with (apparently) six fixed ratios when you use the AutoStick function.
I think all you are doing is manually forcing the transmission into its highest ratio at lower speeds/greater throttle openings than the TCM’s built-in program allows when in fully automatic mode. As Craig said, the only issue is to avoid lugging the engine. However, I think the TCM will probably override your manual selection to avoid this problem. It does so in my Pacifica (conventional 4-speed automatic).
You should be fine. Double check the owner’s manual to see what Jeep says about it. If the don’t say anything, assume that it is OK. I think that Jeep is clever enough to recognize this as an issue and flag it. Do you have a tachometer? What is the RPM level when you cruise in overdrive?
What is continously variable in a CVT transmission? And if it is continously variable why does it have 6 fixed ratios? Probably a terminology situation. A auto stick only situation?
If this car has a D drive gear and another D drive gear that is surrounded by an O, the D surrounded by the O enables the overdrive gears. You should probably drive in the OD drive setting most of the time, even when you are not driving at highway speeds.
CVT is basically a belt between two pulleys that have different diameters at each size. Because the belt used to be made of rubber you didn’t see CVTs much because the belt could only handle a low amount of power without breaking. The “fixed” ratios are just programmed into the computer there are no actual gears in the transmission. Mainly it’s there because some people are bewildered by a transmission that doesn’t shift and prefer having a traditional option.
There is no overdrive selection with an AutoStick shifter, and the there are no overdrive gears, as this is a CVT. As FoDaddy said, the fixed ratios for the AutoStick function are simply computer-controlled points in the continuously variable range of ratios.
The way I understand a CVT is it’s something like a hydrostatic tractor transmission made for a car.
I have never drove nor dealt with one in a car, but on a tractor you basically set the engine to run at a constant rpm because for the motion, you aren’t using engine speed to control gears, rather hydraulic flow to control the speed. Some of the early hydro tractors had a lever that controlled the flow. Farther forward opened up the valve and gave more speed, pull the handle backward and it reversed the flow making the tractor go backwards. Most current models use 2 foot pedals one for forward and one for backwards. It’s very similar to a lawn tractor that has a hydrostatic transaxle except on a tractor the pump is not built into the transaxle like it is with a lawnmower and is driven by the engine’s drive shaft and not a belt. I’ve got a small Massey that’s built like this, actually, it’s one of the first ones built, early 70’s model. The pump bolts up to the rearend and is driven by the drive shaft off the engine. The rearend itself is a 2 speed. You can select neutral, high and low for the rearend. It doesn’t change the pump volume but it does change the gear ratio. These days you can get tractors 40 horsepower and above with hydrostatic drives on them. The larger tractors will have 3 or 4 ranges on them. Changing the range is changing the final drive gear not the flow of oil that drives the hydraulic motor.
There are advantages to having a hydrostatic drive machine and disadvantages. The main advantage is almost anyone with any sense at all can operate a hydro machine. The other advantage is in tight places a hydro machine is going to be easier to handle speeding up and slowing down and changing directions than a geared machine.
The disadvantage is the hydro system sucks power away from everything else. A hydro machine rated at 40 hp is going to be equivalent to a geared machine closer to 60. Another major disadvantage to a hydro machine is it’s complexity v’s a geared machine, particularly on a tractor. Mainly it has to do with the PTO and how the manufacturer chooses to handle that set up with a hydro transmission. Most of the time it’s some sort of electro hydraulic combination.
Hydro machines need a lot more maintenance. You about have to change hydraulic filters with every oil change and you’ve got a lot of fluid to change when required or to leak out if you have a problem. It’s not uncommon for a hydro tractor to be packing 10 to 15 gallons of hydraulic oil in it. The little Massey I have is tiny and it holds 2.5 gallons let alone the 40 to 60 horse and above machines.
I’ve wondered a long time when someone would try to develop a hydrostatic car. I often wondered how many ranges would be required to achieve highway speeds with a system like this. I assume this Jeep if you say it’s a CVT is set up something like a Kubota hydrostatic tractor. The stick shift probably changes the final drive gears while the engine turns the pump and the foot pedal that used to control the gas now controls the flow gate on the hydro pump. I’m curious, does it have a reverse pedal or have they manipulated that into the shifter somehow?
Skipper
In function it’s somewhat similar to a hydrostatic transmission, but the mechanism is entirely different. See FoDaddy’s post above.