'76 mack R power divider

[quantum500]

Trying to figure out if my power divider is good. It is the automatic lockup style. I broke one axle shaft and the power divider will not lock up to move the truck. I'm assuming it has problems. Can anyone clarify?

 

[Iron Horse]

Ive never heard of an automatic type , usually there's a switch on the dash . Which axle did you break , front or rear ?

On Edit , Mack's have automatic "cross locks" , is this what you mean ? As in the cross locks , lock the adjoining axle together and the power divider locks the front and rear diffs together .

 

[Iron Horse]

I should correct myself there , they aren't really automatic cross locks , they work more like Detroit lockers , no spin etc .

 

[lgammon]

all i can remember about when we rebuilt ours is they have these little peanut shaped buggers in there that kind of roll over them selves let the front and back set of axels slip. i think that it is on the output shaft of the front axel. i would think that if you broke an axel in the font one it may have broken more than an axle and is not getting the power to the power divider. or that the divider has been out of it for a while and you were pulling on one axle which is what lead to it breaking the axle

 

[rino]

If I remember correctly the camel back axles on a Mack don't have power dividers. They run full time well actually one axle runs full time until the wheel spins then you get the 1/4 rotation out of each wheel in a cross pattern until the traction is regained! If you have a Mack that handles real well in the mud, this is likely the set up!

 

[quantum500]

I think you are all right. It has one of those little peanut limited slip diffs for the center diff or the "power divider". My question is if there is a broken axle will it destroy the center diff also? To give you an idea of what happened to make the story more rounded. My sister in law did not release the parking brake and kept hammering it untill there was no resistance. Nice huh? Now I get to fix it and I would like a parts list before I take it all apart.

 

[Iron Horse]

I see , are you sure it has broken an axle ? Does the tail shaft turn when you let the clutch out with the engine running while it is in gear ? If not , your trouble maybe further up the line . She would have to have been really giving it a hard time to break an axle . Did it go off with a bang ? Is it possible the transmission has just neutralised ? If it is a Road Ranger , there is a little valve called a Humphrey Valve that can cause this . I don't know about Mack boxes .

They are Mack diffs aren't they ? SP40's had a bad habit of breaking the power divider through shaft without much provocation .

 

[quantum500]

I'm sure the axle is broken. I can send a picture if you would like

 

[Iron Horse]

There's no doubt then , she's a hard man on gear .

 

[OneWelder]

i've run them - if the axle is broke it will not move - it does not work like a lock up power divider
also will not always lock up when you are on ice

 

[td25c]

Sounds like you need an axil and check the power divider Quantum500.I would think the truck would try to move if the p-divider was working.It's possible when the axil broke it shucked the power divider at the same time.Sometimes you can get by cleaning the p-divider up & just replacing the"peanuts".If it chewed the p-divider differetial case up bad that the "peanuts" lock in to,Then it also needs replaced.Hope this helps & good luck repiaring the Bull Dog.

 

[amscontr]

I think the Mack I had the power divider had a filtration system on it and when the filterwas dirty the axles wouldn't lock or maybe the vent.