How Do Secondary Clutches Play A Role In The CVT?

Harvey repairing a primary clutch

How Do Secondary Clutches Play A Role In The CVT?

APRIL 8, 2022

The continuously variable transmission (CVT) is a brilliant piece of machinery. Unlike a geared transmission, CVTs provide power to the drivetrain without manual or computerized shifting. This transmission design allows for a smoother, more powerful ride in most any driving conditions. 

We’ve already taken apart and explained the mechanics behind the primary “drive” clutch, but what about the secondary “driven” clutch? How do ATV/UTV secondary clutches operate in a continuously variable transmission? Harvey’s is here to break it down for you.

How Do Secondary Clutches Play A Role In The CVT?

A CVT is made up of three parts: the primary clutch, a belt, and a secondary clutch. You can think of the secondary clutch as the “catcher” of the continuously variable transmission. 

As the engine accelerates, the drive clutch squeezes on the belt, engaging it and driving it up its tapered plates. This creates a larger “gear” ratio on the front end. The secondary clutch operates in mirror image, giving or receiving belt slack and driving the transmission. 

How does a CVT clutch work? The Secondary Clutch - Overview

Instead of starting in an open position like the primary, the sheaves of a driven clutch begin flush. As the drive clutch begins to shift the belt higher along its sheaves, the tension of the belt pulls down on the driven sheaves, forcing them to spread apart. This means the belt is spinning around a smaller diameter at an increased gear ratio, giving the transmission more speed and power. When the secondary sheave is forced all the way open, the vehicle is in its highest shift state. 

Of course, the secondary clutch is responsible for more than picking up slack and transferring power from the primary to the transmission. It’s sensitive to the vehicle load (how much weight you’re carrying) as well as speed and engine power. 

Parts of the Secondary Clutch

Of course, without any resistance, you would slam open the clutch up all the way each time you revved the gas. That’s 0-100 with no control, which is gonna make for some rough riding.

To compensate for this, a powerful spring holds the primary clutch open. It pushes back against the clutch side sheave. This keeps the shifting of the sheaves and weights to a controlled rate. We’ve already covered the different sheaves, but there are a few more parts crucial to the driven clutch’s inner workings. 

The sheaves are drawn together by a powerful “secondary spring,” which is responsible for keeping a consistent grip on the belt regardless of acceleration. The rating of this spring is also key to proper shifting, as it adds or resists pressure to prevent belt damage or slippage. 

The mobile outer sheave is attached to the rest of the assembly by a cam/helix. This part’s major function is to keep belt squeeze proportional to vehicle load and to resist upshift. Rollers and bushings are attached to a component that compresses the second spring. These resist the movement of the helix’s angled portion. 

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Secondary to None

Harvey’s Mother Clutcher OEM style Polaris secondary clutches come correct and ready for bolt-and-ride action. No need to balance or fine-tune, Harvey himself designed each type of clutch for smooth, responsive performance. With a 1-year guaranteed warranty, Harvey’s comes in clutch for your clutch. 

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