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Vari-Drive on AC T-811


LesH

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Could someone give me advice on the adjustment of the Vari-Drive on the AC Model T-811?? I did it by the instruction book but I cannot get the ground speed to change. I checked the Vari-Drive sheave and it is not "frozen up". Thanks, Les
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Hello Les, My first guess is that there is a problem with belt length. First item to check, start tractor with clutch depressed and latched (Parking Brake On) run for 30 seconds then shut off. Primary belt should be slack on the variator, and the secondary belt should be "deep" down in the variator (Slow position) Reach up and pull down the idler arm on the secondary belt untill it is slack on the variator. You should then be able to slide the center sheve of the variator up against each of the outer sheves, just spinning it on the shaft is not a sufficient check. If it works freely, move on. Start tractor in neutral and let up the clutch, wait 30 seconds then shut off the tractor (Leave clutch engaged) and get under it for a look. The primary belt should be pulled "deep" into the variator, and the secondary belt should be "up" with the outer surface of the belt flush with the outside edge of the variator. This is the "Fast" position. The variator "shifts" as it swings on the mounting arm, controlled either by the clutch pedal or the varitor lever which simply restricts how far back the arm can swing. Under load, such as plowing, the force of tension in the rear belt can force the varitor to open up against the clutch spring, and you can actually watch the clutch pedal drop as it shifts. If the variator sheve is free to slide, and the rear idler spring is working, it all depends on the length of the belts. Report back on what you find, I'm certainly curious.
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