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Camelback Question


TRUE GRIT
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When i bought my 84 r model the rear 38k camelback suspension was shot. I replaced the rubber trunion bushings with urethane, replaced all 4 saddles that house the bushing,new ubolts that torque to 1800 ft lbs. then replaced upper and lower spring pads at each end of leaf spring.the trouble i have still is the axles track off during turning short with a load of about 18 ton of rock on.I also replaced front and rear torque rods. then i talked to a local guru, he says that a 38k rubber trunion suspension should have a side to side or a track bar to keep from off tracking. my truck shows no signs of ever having a track bar. mack dealer said to check for broken frame or trunion. no problems found there.they didnt know about a track bar. i am currently using the truck.i have no driveability problems on the road. it drives and tracks good going down the road. do i need a track bar to fix this, or is this just the nature of the beast? it will only track off at the most a couple of inches. but it is enough for the driveshaft to rub the air dryer. any input would be appreciated.

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I dont know the exact set up you have but most camelbacks were pretty simmilar.

I have seen the track bar mounted on some superliners with camelback. On a single frame, a thick stiffner plate was used on the outside of the rail to help take up the stress from the bar pushing and pulling on the frame.. The track bar is almost the same style that would be used on some air ride set ups. Most of the R models I have seen do not have the track bar.

A little movement is normal. Mack designed it to take up some of the stress that the tandems see on dry pavement turning. I have a broshure on camelbacks and it shows that the rubber bushings allow the tandems to "steer". My rubbers are worn and they move about 2" on a hard turn. If your drive shaft is moving so much to rub the air tank or drier I would think your rears are moving more than 2"?? I have seen some rebuilt camelbacks that move just as much new as before they were rebuilt??

do they move farther one way than the other??

Trent

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I dont know the exact set up you have but most camelbacks were pretty simmilar.

I have seen the track bar mounted on some superliners with camelback. On a single frame, a thick stiffner plate was used on the outside of the rail to help take up the stress from the bar pushing and pulling on the frame.. The track bar is almost the same style that would be used on some air ride set ups. Most of the R models I have seen do not have the track bar.

A little movement is normal. Mack designed it to take up some of the stress that the tandems see on dry pavement turning. I have a broshure on camelbacks and it shows that the rubber bushings allow the tandems to "steer". My rubbers are worn and they move about 2" on a hard turn. If your drive shaft is moving so much to rub the air tank or drier I would think your rears are moving more than 2"?? I have seen some rebuilt camelbacks that move just as much new as before they were rebuilt??

do they move farther one way than the other??

Trent

no not really, looking in youre mirror when turning youll see the outside tread of one of the tires stick out past the other, about the same both ways. if you stop with the truck like this you can actually see the saddles twisted a little on the trunion shaft. i dont know if it is supposed to be or not but my air dryer is mounted inside the frame rails, within a couple inches of driveshaft. i have thought about moving it to fix the interference problem,and maybe someday changing over to a 44k or 60k camelback setup, to my understanding the 44 is on bronze and the sixty is on steel, that doesnt allow any twist. you dont see any dumptrucks around here on 38s mostly 44s

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the camelback system is allowed approx. 3/8" movement when turning. after turning the bogies should align back up. you can help the suspension by putting on a transverse torque rod. you will have to drill and tap the carrier housing to adapt the bracket that the rod bolts to and drill the frame for the rod on the other end. if the bogie still off tracks mack makes offset trunnion pads to install. hope this helps.

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  • 2 weeks later...

hey, my 82 r686st does the same thing on short turns and i have been runnin it for a while like this and i hav had no problems so im not goin to change anything. i have had no problems with the drive shaft hitting anything so im not sure i guess u could do something about it if u want.

Chad

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When you rebushed the trunion, did you replace the retainer rings? There are 2 rings on the trunion bar inside of the caps, did you replace these also. These are there to keep the caps from moving too far and when worn will let even new bushings walk. Even new caps with worn rings will walk.

Jeff

1971 Mack R600 Toterhome "Superdawg"

living the life of leisure pulling

1999 NuWa Snowbird 34+2 SE102 "Dawghouse"

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When you rebushed the trunion, did you replace the retainer rings? There are 2 rings on the trunion bar inside of the caps, did you replace these also. These are there to keep the caps from moving too far and when worn will let even new bushings walk. Even new caps with worn rings will walk.

Jeff

yes, it had about a 3/8 ring on the inside, and about a 1 3/4 ring on the outside, that a bolt goes thru to hold it on. local suspension shop says that when going straight, youre running on the rubbers, when you turn the saddles contact the rings making a metal to metal connection, allowing a little movement, which kinda makes sense. i have had hendricksons and raycos before, and this camelback is very smooth, quiet, and goes better off road than any of them that i have had. which brings up another subject, this is my first mack so i am still learning about them, but this truck has no power divider. both axles pull all the time to my understanding. makes it go off road better im sure. other trucks ive had i would unlock power divider as soon as i got to blacktop. seems like it would be hard on something on the mack. thanks for everyones input on this subject. doug

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It has a power divider. It doesn't have a manual control. The power divider will engage itself as needed and provide power to the front axle. Running on the road there is only power to the rear axle.

That is a common ideal that I have see and told by truck driver for my 42 years of working on trucks that it will pull on the rear only. It pulls on bothl rear equaly because it has a power divider with a air lock or not.

Glenn

glenn akers

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on a side note. I found that I can engage the power divider (in the mud) by taping lightly on the brake pedal. an old trucker told me to try it and it works pretty well if you are not stuck badly. I have used that a few times to get rolling in some slick (*&^. It works good as long as you are doing it safely at a slow rpm.

anyone else do this?

Trent

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I drove a 1970 vintage R model tandem at Dakota County Vo-Tech back in '77 that had Mack rears with no power divider on camelback suspension. Mack claims that the camelback flexes like railroad car trucks, bringing the inside wheels closer together and spreading the outside wheels as the spring compresses from the swaying load. Thusly the inside and ouside wheels turn at about the same spped and reputedly no interaxle differential is needed. When Mack started offering their tandems on other's suspensions they had to develop an interaxle differentilal, and the overrunning pawl design they use is a most elegant one.

I drove a 1970 vintage R model tandem at Dakota County Vo-Tech back in '77 that had Mack rears with no power divider on camelback suspension. Mack claims that the camelback flexes like railroad car trucks, bringing the inside wheels closer together and spreading the outside wheels as the spring compresses from the swaying load. Thusly the inside and ouside wheels turn at about the same spped and reputedly no interaxle differential is needed. When Mack started offering their tandems on other's suspensions they had to develop an interaxle differentilal, and the overrunning pawl design they use is a most elegant one.

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  • 2 months later...

When i bought my 84 r model the rear 38k camelback suspension was shot. I replaced the rubber trunion bushings with urethane, replaced all 4 saddles that house the bushing,new ubolts that torque to 1800 ft lbs. then replaced upper and lower spring pads at each end of leaf spring.the trouble i have still is the axles track off during turning short with a load of about 18 ton of rock on.I also replaced front and rear torque rods. then i talked to a local guru, he says that a 38k rubber trunion suspension should have a side to side or a track bar to keep from off tracking. my truck shows no signs of ever having a track bar. mack dealer said to check for broken frame or trunion. no problems found there.they didnt know about a track bar. i am currently using the truck.i have no driveability problems on the road. it drives and tracks good going down the road. do i need a track bar to fix this, or is this just the nature of the beast? it will only track off at the most a couple of inches. but it is enough for the driveshaft to rub the air dryer. any input would be appreciated.

Well my brothers put about 5K in our R model camelback last summer counting the springs-sure made VDOT happy and it off tracks a fair amount doesnt seem to hurt anything-its 38ks with no diff lock and it will hang up with 1 wheel in the air-however my exboss had 2 -88' r's with bronze bushings &38's +no diff locks& will pull both axles and these things would shed rubber rather then offtrack and yes they pulled tags and spent most of the time offroad overloaded[ didnt like the 300L's but those things sure had some grunt] one school of thought around here is dont tight turn if you dont have to[but who doesnt run lock to lock?-Kevin

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  • 10 months later...

I was told the same thing as Lmackattack. Light pressure on the brake pedal or trolly will engage the divider. I have tried this when opposit axels are spinning, sure enough the others start to rotate. Very handy piece of info to have, especialy around this time of year. Use common sense! under low power at a crawl to avoid any damage. This tip has helped me walk out of some mud holes that other brand trucks would have needed a wrecker to get them out!

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  • 12 years later...
On 1/14/2006 at 5:54 PM, TRUE GRIT said:

When i bought my 84 r model the rear 38k camelback suspension was shot. I replaced the rubber trunion bushings with urethane, replaced all 4 saddles that house the bushing,new ubolts that torque to 1800 ft lbs. then replaced upper and lower spring pads at each end of leaf spring.the trouble i have still is the axles track off during turning short with a load of about 18 ton of rock on.I also replaced front and rear torque rods. then i talked to a local guru, he says that a 38k rubber trunion suspension should have a side to side or a track bar to keep from off tracking. my truck shows no signs of ever having a track bar. mack dealer said to check for broken frame or trunion. no problems found there.they didnt know about a track bar. i am currently using the truck.i have no driveability problems on the road. it drives and tracks good going down the road. do i need a track bar to fix this, or is this just the nature of the beast? it will only track off at the most a couple of inches. but it is enough for the driveshaft to rub the air dryer. any input would be appreciated.

A transverse torque rod (1RY48P23 or equivalent 1RY351P11 - 2 different vendors of same) was not originally deemed necessary for on-road highway models with 38k suspensions. It simply isn't necessary, like it is for vocational. That said, we wrote a service bulletin outlining how to add a transverse torque rod if desired. It obviously will extend the life of the trunnion insulators. You need a 44RU11192 spacer plate behind the frame-mounted bracket with single frame trucks.

Always apply 20 weight non-detergent motor oil, per the Mack service bulletin on the subject, when installing Mack trunnion insulators.

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  • 2 weeks later...
On 3/24/2020 at 10:11 AM, amck said:

About how much time does it take to rebuild a camelback suspension?

I made a youtube video depends on what you got to do and what capabilities and tools you are working with, the video will tell you.

 

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Robert

"I reject your reality and substitute my own."

 

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