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Was moving my R-612ST around yesterday and found it strange I could not back up a slight incline around the rear of the shop where I park a lot. It was raining and slick, but the tire slippage was a bit more than I'm used to. Adjusting my spot mirrors so I could see the drives from the seat, it was clear the automatic power divider was not operating and the noise of it slipping was evident with the window down. Don't really have time to work on it right now but will need to before going back to work with the truck later in the summer. I'm planning to haul sod for my part time employer and will need both axles driven when off road.

Never been into the rears of this truck so know nothing about the innards conditions. I'll probably pull it apart before ordering anything to ensure the outer cam and cage condition before tying up the spot in the shop.

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I did install the inner cam, peanuts, (wedges) and an O ring seal for the housing and the problem appears to be repaired. I can back up both the original hill, and a much steeper one without tire slippage on dry ground now. Never could back up the steep hill in the past so an improvement for sure. Gone is the noise from the slippage also. Pretty easy job once the driveshaft is out of the way.

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Hey! I got a 1996 Mack CH613 from my grandfather just before he passed away last August, he didn’t really tell me a whole lot about what was wrong with the truck but he did tell me that it had been sitting for 11 years and he had parked it beside his garage when he thought the peanut gear or peanuts went in the differential and he told me that a Mack mechanic told him it was the peanut gear, so just recently me and my dad went to see if we could get it going again, long story short after changing the fuel filters and making sure it wasn’t seized it fired up and when we tried to move it, I put it in gear and nothing happened so I flipped my power divider on and it would move but seemed to be slipping and about every 25-30ft it would make a loud Bang noise and feel like something was binding in the read end, I don’t know much about Mack differentials but if it is a peanut gear what would a peanut gear cost? and what exactly does a peanut too? 

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Theres 2 styles of power divider locks on Mack trucks. Both styles are mounted on the front drive axle housing where the driveshaft mounts. The style rob has is an automatic engaging type, no switch to hit it works when it's needed. Assuming you have Mack rears, you have a style that you need to engage manually via the dash switch. Never engage it when you have a wheel spinning, great way to tear it up. 

The "peanuts" are what engage in the power divider to require the rear axle to get power. They could be shot, but you could also have a blown rear differential bearing. There are inspection windows on the left side of the differentials. Open them up and see if there's junk inside. Ring gear could be missing teeth. You could have a broken axle shaft too. 

When the PD is engaged on Mack rears, at least one wheel on each axle has to spin for you to get stuck.  Some ABS systems take offroading a step further and will engage the brake on any individual wheel that starts to spin faster than the other drive wheels. This helps force power to wheels that aren't spinning because they have better traction. 

I've never worked on a power divider, I just know they're great.

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