Power Divider

[charlie]

I have an air lock power divider and I've tore the cam and the peanuts up twice in a year to where it overides and slams on the peanuts. Do any of you know what could be causing this? Getting expensive!!! This last time I forgot to back up when I unlocked it and it unlocked about 5 miles down the highway with a slam. Might have messed it up then don't know, but didn't think they would be that weak.I haul logs, so it takes a beating anyway,but I've run macks along time and never had this kind of trouble with them.

[HK Trucking]

I have an air lock power divider and I've tore the cam and the peanuts up twice in a year to where it overides and slams on the peanuts. Do any of you know what could be causing this? Getting expensive!!! This last time I forgot to back up when I unlocked it and it unlocked about 5 miles down the highway with a slam. Might have messed it up then don't know, but didn't think they would be that weak.I haul logs, so it takes a beating anyway,but I've run macks along time and never had this kind of trouble with them.

Mismatched tire diameters on one drive axle vs the other drive axle?

Contrary to how it's done with "generic" trucks where you would keep tires matched across each drive axle, on a Mack with the cam & wedge power divider you keep all the larger tires on one side of the tandems and all the smaller ones on the other side of the tandems, so as not to cause a great discrepancy in revs per mile on front vs rear drive axle.

In the US, where we drive on the right side of the road, keep the larger tires all on the right, and the smaller tires all on the left to compensate for the crown of the road.

.

[Lmackattack]

hmm. on all the air lock power dividers I have used all you had to do was get some slack in the drive train to have it release. If I had it in and was going through mud then exit on to a street, the PD would unlock as soon as I let off the power or the truck coasted a little.(switch in the off position) Backing up will also do the trick but I have never had to as long as I unloaded the stress on the drive line and was not in a turn.? most times I turned it off 10' before I hit the pavement unless I needed it to get out.

A few rules I have learned and told about with air power dividers.....

never put it in with the tires spinning

Most times the truck should be stopped or rolling in a straight line at slow speeds to put it in.

dont drive on pavment with it in

turn off before you reach hi speeds.

dont put in at high speeds.

tire size across the axel is important but hurb had just pointed out a great example that I did not know about mack power dividers.(thanks Herb)

[Packer]

I've always been told that:

A)Measure all the tires around, then match them within an inch.

B)As Herb said, biggest on right hand front drivers

Next biggest on right rear drivers

Then left rear

Smallest two tires on left front.

That system worked for years, for me.

Good mileage from tires with little scuffing or funky tire wear.

Make sure the tire pressure is checked as you measure the tires.

Somewhere, in a 'Operating Manual' I got from the Mack Museium, that's how it was discribed.

Might have to take a look and find it again.

Packer

[charlie]

Thank you! I'll check the tires. This is getting to be a headache.

[charlie]

Think I'll find me an R model mack rear with no air divider and put in it!

[HK Trucking]

Having or not having an air operated lock out on the power divider would have no effect one way or the other on wear of the "peanuts", except that when the air lockout is "locked" there is no wear on the peanuts because with the power divider locked there is no relative motion of the cams vs peanuts. Locking the power divider will cause torsional "wind up" of the diffs & axles when on a hard surfaced road however.

Something is going on if the power divider is wearing out twice within a year.

Besides the mismatched tire scenario, is there a possibility that the ratio of the front diff is slightly different than the ratio of the rear diff? I've seen that happen where someone would inadvertently install the wrong ratio when rebuilding a diff, then when the truck was operated the power divider would clunk and bang (and wear quickly) trying to compensate for the discrepancy in revs per mile of front diff vs rear diff.

[Gambi80]

I'm gonna have to print this out. I would just swap the back drives to the front and vice versa. How much difference does it make, if any, if I always buy 8 new matched drives instead of having mis-matched tires?

[Lmackattack]

Gambi..If you have a matched set your fine. The diffrence is that when the tires are of diffrent sizes the Diff spider gears are compensating by spinning all the time. Its normal in a turn to have those gears spin on a open axel but just driving down the highway it puts more wear on them when they should be doing very little. The power divider will also wear out as the rear axel may be slower than the front (or vise versa). the Divider components will try to compensate for the speed diffrence and wear early as they should not be needed when driving down the highway. I notice some old macks can spin all 4 corners in the mud on a rebuilt tight drive line where worn out rears will spin 1-2 wheels and the powerdivider may not lock in as it should.

Herb, please Correct me if im worng but with macks power divider you only get 2 drive wheels "locked" in? One wheel on the FR and the other on the RR axel?

With a diff lock and power divider you should have 3 wheels locked in?

Trent

[HK Trucking]

I'm gonna have to print this out. I would just swap the back drives to the front and vice versa.

That wouldn't solve anything, you'd still have the same discrepancy in tire diameters, only in just the opposite wheel positions. You have to keep all 4 on the same side of the tandems as nearly matched as possible.

How much difference does it make, if any, if I always buy 8 new matched drives instead of having mis-matched tires?

That would be the best case scenario, although even a set of 8 identical drive tires could still be slightly different in diameters.

.

[Gambi80]

Well...I've never had any trouble I guess.

I do buy all 8 at the same time and 'rotating' them front to back, back to front gets them worn evenly and enough so that I can put 8 new tires on at once...though I don't like the bill for that.

[charlie]

I'm using after market parts and someone told me to use mack parts instead, there better. Said that's why I'm having trouble!

[Arvin Cristi]

hey guys, an additional question regarding the lockers and power divider... is it possible to buy just the peanut looking thing and the cam inside the shaft? because i'm currently rebuilding my superliner, which my old driver screwed up( had to replace the rear-rear pinion drive and worm gear, replaced fifth wheel, had to re work the entire cab)considering that i am all the way in the Philippines, i just want to be sure of the things that i buy, since shipping all the way here cost an arm, leg, and a waist!

[rhasler]

hey guys, an additional question regarding the lockers and power divider... is it possible to buy just the peanut looking thing and the cam inside the shaft? because i'm currently rebuilding my superliner, which my old driver screwed up( had to replace the rear-rear pinion drive and worm gear, replaced fifth wheel, had to re work the entire cab)considering that i am all the way in the Philippines, i just want to be sure of the things that i buy, since shipping all the way here cost an arm, leg, and a waist!

From the Mack service manual 13-105:

"The frictional forces created by loads imposed on the cams and wedges cause moderate scoring on the highly stressed rubbing surfaces of cam tracks. This is a normal condition. Replace the affected cam and wedge items only if working surfaces are badly worn, pitted, scored or cracked. Replace the driving cage member if it is damaged or the wedge hole diameter has worn more than 0.010 inch (0.25 mm) over the original limit.

Never run new wedges against a used inner cam or vice versa. It is permissible, however, to use slightly worn outer cams and driving cages during rebuild. Always replace wedges in matched sets. Do not mix wedges from different sets."

[Arvin Cristi]

From the Mack service manual 13-105:

"The frictional forces created by loads imposed on the cams and wedges cause moderate scoring on the highly stressed rubbing surfaces of cam tracks. This is a normal condition. Replace the affected cam and wedge items only if working surfaces are badly worn, pitted, scored or cracked. Replace the driving cage member if it is damaged or the wedge hole diameter has worn more than 0.010 inch (0.25 mm) over the original limit.

Never run new wedges against a used inner cam or vice versa. It is permissible, however, to use slightly worn outer cams and driving cages during rebuild. Always replace wedges in matched sets. Do not mix wedges from different sets."

hey rhasler, thanks for the quick reply, well the wedges are all worn out and some are even chipped, so i guess that means having to buy a new set, as for the outer and inner cam's for some reason these escaped with just some very minor pitting. and the cage seems just fine... i found my parts book, but there is no number on the wedges. it seems these are sold as a set with the driving cage. do you have any leads as to where i can find just the wedges?

[rhasler]

hey rhasler, thanks for the quick reply, well the wedges are all worn out and some are even chipped, so i guess that means having to buy a new set, as for the outer and inner cam's for some reason these escaped with just some very minor pitting. and the cage seems just fine... i found my parts book, but there is no number on the wedges. it seems these are sold as a set with the driving cage. do you have any leads as to where i can find just the wedges?

The wedges should only be replaced as sets along with the inner cam. Wedges were available as a matched set w/o cage. I think the part number for a CRDPC92 rear end is 30KN112, that part number has likely changed, but I think the wedge set is still available.