December 22, 2017 at 11:54 am #10143
My 07 Jeep Compass was quite quick and zippy when I first got it. Now it seems to hover around revs as if its sturggling to find the next gear, is doesn;t accelerate as quickly anymore and feels as though it’s being held back. No noises or smells, has just ‘slowed down’
96000 km on the odometer
CVT transmissionDecember 24, 2017 at 12:43 am #10151
Your problem is with the CVT. The initials stand for a continuously variable transmission. It is quite a different device than a standard automatic transmission. On paper, of course, they look like the same type of device because their usage is only to move the power from the engine to the wheels and then to move the vehicle up to speed.
In a normal automatic transmission there are a number of standard items that most drivers know or should know about. For example, when the engine spins up to speed, the power generated is transferred to the transmission via the torque converter and impeller and then on to the solenoids (responsible for choosing the proper gearing) and valve body where the transmission fluid travels through a series of galleries that enable the choice of gears.
As all of this is going on, the input shaft continuously supplies the transmission with power so that all the devices named function full-time. Meantime, a series of clutches engage to enable the vehicle to move up to the next gear as the bands tighten making it happen. At this point, the power flows to the planetary gears so that they can assume the configuration that has already been ordered solenoids.
If this sounds complicated, it is, but, the transmission control module and other electronics know when things are supposed to happen so everything stays in order and the transmission functions properly.
Once the gearing is chosen, the power is routed to the proper gears and then on to the output shaft which spins up the differential as the power is split between either front wheels or rear wheels or both.
A CVT is a complexly simple device. Its goal is to move your Jeep and usually it does quite nicely. The issue with CVTs is that over time — usually more than 62,000 miles or the 95,000 km that is on your SUV — CVTs tend to wear out because of the fact that they are constantly engaged. In other words, there is no gearing choice. When you push on the gas pedal of a CVT, the engine supplies power and the CVT — a large multi-turbine-like device — uses only those bands that it needs tightened so that the particular turbine is engaged as the CVT moves up to cruising speed.
Think of the CVT as a long barrel-like device with a series of turbines that are engaged by a series of bands that tighten up as they are called on to move your SUV up to speed. Since they are continuously engaged, your transmission has no discreet gears — Park, Reverse, Neutral, Drive, Low, for example — other than Drive, Reverse and Park.
This enables you to press the gas and the SUV should rocket ahead, as you said. What I think is happening to your Jeep is that the one or more of the band-like device that engage and and keep things moving has failed or is on its way to failing. Because it is, your Jeep is no longer operating very efficiently. Instead, it’s pretty much not working at all.
You will have to get to a service area, if you can drive it or you may have to have it towed or trucked in, so the techs there can run a diagnostic to see where the problem is and what it will take to fix it. At this point, I don’t know how extensive the damage to your CVT might be so I won’t venture a guess as to cost other than saying that if you have to replace it, the cost should be comparable with replacing a normal automatic — about $4,000. Let me know what happens.
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