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Adjusting Eaton Positraction

Last month, I talked about the strengths of the new Eaton positractions. This month I am going to talk about rebuilding an Eaton positraction to be more or less aggressive to suit the needs of the user, and give a few tips on how to set the clearance. By using different clutch pack designs and different spring rates, a positraction or limited slip can be made to act differently. Using a clutch design with more or fewer plates, or plates with different friction characteristics, can alter the behavior of the unit. The characteristics can also be adjusted by using stronger or weaker springs, which will increase or decrease the preload on the clutch plates. A stronger spring will help the unit hook up better in situations where extra power transfer is need, but too much spring pressure can cause clutch chatter.

The new Eaton positractions come stock with carbon fiber clutches and 400 lb. springs. This combination gives good power transfer in extreme conditions and does not chatter during everyday driving. Some people, however, may be looking for more aggressive off-road performance, in which case there are several options to make the unit hook-up even better.

Adjusting Eaton Positractions Adjusting the clearance is the hardest part of setting up an Eaton positraction correctly. Measuring the clearance correctly involves compressing the clutch pack and then placing the dial indicator correctly. I have found that placing the dial indicator plunger on a pinion gear tooth near the side gear gives a fairly accurate indication of what the final assembly clearance will be. Adjusting the clearance involves adding or subtracting shims between the case and the clutch pack. Adding shims will decrease the clearance, and removing them will increase the clearance.

The spider gear clearance can effect the characteristics somewhat, but only a limited amount. For most Eaton positractions with new spider gears and new clutches, I set the side gear clearance at 0.010" to 0.015", with no more than 0.002" variation from side to side. For units where I am reusing partially worn clutches and side gears, I set the clearance at 0.014" to 0.018". Setting the clearance tighter can make the unit more aggressive so that it hooks up better, but if the clearance is too tight it can be very difficult, if not impossible, to assemble. Setting the clearance too loose will cause problems with the tooth contact and can cause the unit to chatter. It took me a lot of practice and experimentation to get good at adjusting these positractions, so be patient and don't expect to become an expert overnight.

There are four different spring rates available for Eaton posi's. They provide 200, 300, 400, or 800 pounds of preload. Eaton makes the 200, 400, and 800 pound designs, each as a complete package with four springs and two plates. GM makes the 200 and 300 pound designs, which come as four separate springs and two separate plates.

There are currently four different clutch plate designs available, three of which are worth considering. We will begin with GM's service pack which uses 18 all-steel clutches with cut-outs for oil. These clutches tend to chatter, and the cut-outs that are supposed to decrease chatter make the plates weak and prone to breakage. The new 14-plate carbon fiber clutches from Eaton are my favorite. This design hooks up very well off-road and does not chatter when used with the 400 lb. springs. There is also an 18-plate, all steel design that does not use cut-outs. This design hooks up very well for off-road use and does not break. However, it does tend to chatter when used with 400 lb. or 800 lb. springs. Use these clutches for drag racing or an extreme off-road application where long life is important and chatter will not bother the driver. The most aggressive design from Eaton uses 22 plates, and chatters with any spring combination. These were designed for GM racing applications and work well until the thin tabs that engage with the case start to wear out. Use this package when extreme traction is needed and the clutches can be serviced often.

Randy's Ring & Pinion carries the full Eaton line of complete units and all of the parts to rebuild or adjust them. Or, for more information and a list of other distributors, visit www.torquecontrol.eaton.com.

The content of this page has been provided courtesy of Randy’s Ring & Pinion