mack R model odd story

[lgammon]

now in the other post we were talking about the rearends on the macks it came back to me why we where in ours. well i;ll start at the beginning. we bought a 86 mack r model at an auction in Atlanta. it was a road tractor, 300 hp two pole 6 speed. we brought it home and had a dump bed put on it. we started using it as out primary truck. we pulled a 943,941,580sl, and hauled rock and such. well some times when you really loaded it down, a big wet load of dirt or shale. you would hear a loud banging, like some one hitting the bed with a hammer, when in a HARD pull. mmm well we start looking, checked the magnets in the rear ends and trans plugs, nothing. we could not find anything. so we lived with it for a few years. about 3 years later i was fixing a yard, it had a lot of rocks in the yard, which i loaded them in the truck, about 3/4 full. i had the 943 and a 236 skid there which i loaded them both on the trailer behind it. i know this is WAY over loaded but the we where just going 10 or 15 miles down the road to the next job and we needed both machines and it was a good place to take the fill. in the way there was a good hill we had to pull. going up the hill it sounded like you where taking a backhoe bucket and beating the side of the dump bed!!! but it kept pulling so we went on to the site. so now i am going to let you guess what it was that was wrong. i will tell in a day or so

 

[heavylift]

torque arms and bushings....
walking beams...
bent driveline...

 

[lgammon]

nope but on the right end of the truck

 

[WesternStar]

Was a rim spinning on the hub? Had an old Mack once with the 5 spoke wheels, the nuts weren't kept tight and the hub spun inside the rim.

 

[Steve Frazier]

Was the pinion jumping on the ring gear? I had this happen on an old Mack once, it made a horrific noise until it let go altogether.

 

[RTSmith]

Going to be a long day or two. My curiosity is running already! By the way- I'm with wheels on this one too. I am curious to hear more about Steve's pinion. Would think that with that much clearance somewhere, it would never work at all....Unless the pinion had a bad bearing letting it walk fore & aft....

 

[Steve Frazier]

I wasn't around when the truck was tore down to see what actually caused it, I was the driver. I was climbing a slight hill with a load of gravel on and it made a few bangs and lurches. There was no place to pull over so I tried to get to a spot I could get out of traffic but it let go before I could. The pinion snapped on the front rear, it was all rounded off like it had spun before snapping.

 

[Steve Frazier]

I also was in a truck where the axle broke, but it was at such a jagged angle that it held in place for a while before it spun. I was bobtailing with that one, someone who had it before me must have broken it.

 

[Orchard Ex]

someone who had it before me must have broken it.

Where have I heard that before?

 

[OneWelder]

pawls slipping by

 

[td25c]

My buddy has a mack log truck that has made a popping noise in the rear ends for awhile now on hard pulls,and he keeps using it .We havent tore into it yet but we are guessing it's the automatic locking power divider locking in on a hard pull then slipping out making the popping noise.Thats my guess on your truck lgammon.

 

[John C.]

You didn't mention what kind of suspension. I'm assuming it's a camel back. An 86 model would probably have standard diffs instead of the worm wheels.

I'm guessing the suspension has set down low enough to let the drive lines straighten and now they have lost all their clearance. Possibly the rear drive line has spun through all the splines?

Just guessing here.

 

[Dominion 410]

R model

I've run across the odd wore driveshaft spline that might cause the noise.Mack rears are generally pretty tough but have seen broken axles in them.Mainly in 38,000lb.,never in the 44's.Usually crack them loaded,finish them off empty-especially when just starting to reverse.

Dominion:canada

 

[lgammon]

ok now for the part that i wouldn't have believed on less i counted the ring and pinion myself!! you guessed it to different rear ends!!!! the first axel started leaking around the top and we pulled it off to reseal it and i told dad lets count them to see what the gear is, and that got us thinking .........well we pulled the other and it was a different rear end. i don't remember what the numbers were but they were fairly close, one size off. now who would think that the truck would make it out of the lot much less over 3 years of driving.

 

[lgammon]

who thinks there pete or kw would do that?? i love these ole rough and tough macks.

 

[Dominion 410]

Mack

I've heard of that problem once before.Must have been some strange noises happening there.Did you manage to correct it?
With regards to Mack durability,they are still at the top of my list.Can't seem to wear out those old R models.I just saw an old R-600 with Maxidyne engine and six speed trans the other day.Tri-axle block truck with boom,pulling a tandem wagon with a converter.Fully loaded front to back.44,000lb Mack rears on camel-back suspension.Had the two piece axles-the flanged end of the axle is seperate from the axle shaft itself.That truck must have been a good 25 years old and still doing a day's work.Used to call those things the "mortgage maker".Never win a race,but at the end of the month it will make your mortgage payment".
A wise man once told me ''You don't buy a truck from someone who makes cars or farm tractors.You by a truck from someone who builds trucks.

Dominion:canada

 

[Mack185]

We had an old 84 Peterbilt that would clunk every time you would give it throttle, after shifts mostly. The Driveline was so old and wore out you would have to give a little throttle to tighten it up before you gave it anymore juice. If you didn't, it would pop and clunk like a mother. I would just look everything over, something is probably just loose and/or worn out.