Breaking Spring Brake tubes

[simp5782]

Ok so over the past 2 months I have broken 6 of the tubes that hold the spring brake to the brake backing plate. 1 was due to a blowout. then I lost two over about a 4 week period and not on this past 1200mile trip I broke off 3 along with 3 of the mount/hold tabs. last Monday I pulled and replaced both wedges on the front tandem and installed the tubes correctly and made sure they were secured with the u bolts. the tabs were in good condition. Somewhere after the Monteagle mountain and Paducah KY I noticed my brake pedal was hard on applying it but stopping was slow. So I got out and saw that atleast 1 of them was broken then. After continuing up into Illinois and then returning home I was slow and careful even at night with no traffic. Upon inspection all 3 of the holding tabs were broken at the tops.

So what could be causing this? I have spoken with both 73M819 and CSMDavis and we are out of ideas. Backing plates are on tight. tabs were good. u bolts were tight. Excessive hard braking? or just the road pounding from all the bumps? I have discussed having a heavier duty holding tab made as well as installing shocks. I don't think there is any axle walk while driving. It has become so frequent that now I carry cap off plugs for the air lines so when it brakes off I can simply cap the lines and remove the chamber so I have air pressure.

 

[gimpyrobb]

Loose screw between the seat and steering wheel...






















Just sayin.

 

[doghead]

Is the ubolt support as close to the can as possible?

NOTE: Support brackets must be used on traileraxles where the chambers have tubes equal to orlonger than shown in Figure 4.10. Weld thebracket to the axle. Attach the tube with a U-boltand saddle bracket as close as possible to thechamber. For information on welding, refer toMeritor Maintenance Manual No.

http://manuals.chudov.com/Grove-Rough-Terrain-Crane/Meritor-Wedge-Brakes.pdf

I would fabricate new heavier brackets(possibly welded to the axle housing.


Maybe check your drums for run-out?

 

[gimpyrobb]

Seriously though, have you thought about using a pair of the steadying brackets instead of 1? Maybe there is some kind of twisting going on, that 2 would eliminate. I don't mess with air brakes, so It might be a dumb idea.

 

[doghead]

How many different locations/positions have they broken from?

 

[Floridianson]

You said installed correct. Thought the install of tube was all the way in back out one turn?

 

[simp5782]

Drivers front tandem side 2x. Front tandem Pass 3x. Rear tandem Pass 1x. I have set the ubolt as close to the can with the cylinder as tight as I can get it while being able to access the air ports facing the top then I run the nut down. I have them tight. I am also carrying roughly 5 tons of things in the bed as well. I haven't measured the drum run out yet. shoes are at 70%. Wedges were free. One had a broken spring the first time. Replaced it.

 

[simp5782]

You said installed correct. Thought the install of tube was all the way in back out one turn?

I tighten them down till they stop then back out till the air port faces the top so it can be accessed.

 

[Floridianson]

If it is one turn out then one turn it should be. To get ports right then just adjust the top canister with clamp loose with brakes caged.

 

[simp5782]

If it is one turn out then one turn it should be. To get ports right then just adjust the top canister with clamp loose with brakes caged.

The one port is actually made into the tube.

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[Swamp Donkey]

I got a good look at the underside of your truck at the rally and formed an opinion of why the things that were broke had broken, which were both rear main leaf springs and the torque rod mounting bolts. I think I hit on it a little while we were talking.

Now you have the spring brake tubes breaking repeatedly. There are two common things between all these parts, aside from them all being in the rear of the truck.

1. They all require friction to work properly and stay secured. This includes the leaf springs, in both instances.

2. Every suspension part behind the transmission has been saturated in transmission fluid for an extended amount of time due to the leak.

Without friction, things move. When you have movement, you have forces being applied to things not designed to take them in that manner. Leaf springs should never be lubricated because they require friction to withstand the forces they endure. Bolts and mounts on the axle require friction from the axle tube to stay in place. Lock nuts for the brake tubes require friction to keep the tube tight.

The rear underside of your truck is saturated with oil. You've already had a torque rod mount come completely loose. All the brake tube brackets are mounted to the torque rod mounts. I would bet you have a lot of things moving back there due to the oil. It wouldn't take much movement to break a tube. I'd suggest a super thorough steam cleaning with degreaser of everything in the back. Then go back and retorque all the suspension related stuff to spec.

I dealt with this same thing on an 85 Chevy K10. It started with a small powersteering leak from the steering box that saturated the front left leaf springs. I had problems with those U-bolts staying tight then 2 of the springs broke about a month later. Repaired all that but didn't fix the leak. It eventually got bad enough that it started saturating the rear of the truck. The transmission mount kept getting loose, then the rear U-bolts on the left side wouldn't stay tight and finally ended up with left rear spring failure while pulling a heavy trailer. Repaired everything again, cleaned it spotless and replaced the steering box. Never had anymore issues.

I think the transmission leak is the problem, the heavy loads are aggrevating it and everything else is the result of being saturated in oil. Feasible?

 

[73m819]

I still think it is a axle issue, this is the same axle that you had the torque rod mount come loose, along with major vibration you feel, I truly feel that you will keep breaking stuff around #2 axle till you find out where the vibration is coming from, I will guess you WILL find that #2 axle is the source, this could be internal or external (a bent axle tube, axle, hub bearing, ect.),, internal could be a bearing, chipped tooth, ect., #2 axle carries the drive load for both rear axles, I am guessing that the first reduction is where you will find the vibration source.

Just because something is wet with oil is NOT a reason for mounts, bolts, ect. coming loose, proper torque will keep things tight, vibration WILL loosen and break everything, just think of how a air impact wench works, once a bolt, mount, ect is loosened by viberation, they WILL not stay tight no matter what you do because the bolt WILL be stretched, the mount holes WILL be wallowed, the metal around the vibration looseness WILL be fatigued due the pounding caused by the vibration. The longer the vibration exist the more damage and the seriousness of the damage keeps multiplying on itself.

 

[doghead]

I didn't see any mention of vibrations.

 

[simp5782]

I still think it is a axle issue, this is the same axle that you had the torque rod mount come loose, along with major vibration you feel, I truly feel that you will keep breaking stuff around #2 axle till you find out where the vibration is coming from, I will guess you WILL find that #2 axle is the source, this could be internal or external (a bent axle tube, axle, hub bearing, ect.),, internal could be a bearing, chipped tooth, ect., #2 axle carries the drive load for both rear axles, I am guessing that the first reduction is where you will find the vibration source.

Vibration has been sourced Ron. It is the transfer case.

 

[simp5782]

I got a good look at the underside of your truck at the rally and formed an opinion of why the things that were broke had broken, which were both rear main leaf springs and the torque rod mounting bolts. I think I hit on it a little while we were talking.

Now you have the spring brake tubes breaking repeatedly. There are two common things between all these parts, aside from them all being in the rear of the truck.

1. They all require friction to work properly and stay secured. This includes the leaf springs, in both instances.

2. Every suspension part behind the transmission has been saturated in transmission fluid for an extended amount of time due to the leak.

Without friction, things move. When you have movement, you have forces being applied to things not designed to take them in that manner. Leaf springs should never be lubricated because they require friction to withstand the forces they endure. Bolts and mounts on the axle require friction from the axle tube to stay in place. Lock nuts for the brake tubes require friction to keep the tube tight.

The rear underside of your truck is saturated with oil. You've already had a torque rod mount come completely loose. All the brake tube brackets are mounted to the torque rod mounts. I would bet you have a lot of things moving back there due to the oil. It wouldn't take much movement to break a tube. I'd suggest a super thorough steam cleaning with degreaser of everything in the back. Then go back and retorque all the suspension related stuff to spec.

I dealt with this same thing on an 85 Chevy K10. It started with a small powersteering leak from the steering box that saturated the front left leaf springs. I had problems with those U-bolts staying tight then 2 of the springs broke about a month later. Repaired all that but didn't fix the leak. It eventually got bad enough that it started saturating the rear of the truck. The transmission mount kept getting loose, then the rear U-bolts on the left side wouldn't stay tight and finally ended up with left rear spring failure while pulling a heavy trailer. Repaired everything again, cleaned it spotless and replaced the steering box. Never had anymore issues.

I think the transmission leak is the problem, the heavy loads are aggrevating it and everything else is the result of being saturated in oil. Feasible?

Transmission leak has been fixed. Leaf Springs have been fixed. New u bolts . They are still dry. The mounting tabs actually mount to the stop plates for the leaf springs and not to the dogbone. I honestly think the rear dogbone clamp was just not tight from the get go since the truck was fresh out of rebuild when I got it in 2015. 3hrs and 30miles to be exact on the truck. I replaced it and installed nylon lock nuts and have not had a problem since. I replaced the hold down brackets for the brake tubes when I did the leaf springs since two of them had been hit by the leaf spring walking out. They were not saturated nor were the u bolts on this instance. The one spring chamber had some grease left over on it. Two of the brake tubes broke off with the tab still attached and the u bolt still attached. Just right near the backing plate. You couldn't even tell unless u looked at it close.

As far as the vibration. It has been sourced to the transfer case. one bolt has stripped out. causing a slight dip in the case. This is about to be swapped out. The nut is actually trying to pull thru the metal mounting plate. I assume this is the result of torque.

I did put the impact on ALL suspension bolts when I did the leaf springs to ensure everything was tight. Maybe they just got too tight? I am going to evaluate the 20 degree angle that the meritor catalog Doghead posted says.

 

[Floridianson]

and the plot thickens. Good to know info above.
Ron Swamp Donkey got a good look at the truck. I would start at the trunnion bearings and work out the spension with all good useable stuff replace bad. No bad anything then see what you find.

 

[simp5782]

and the plot thickens. Good to know info above.
Ron Swamp Donkey got a good look at the truck. I would start at the trunnion bearings and work out the spension with all good useable stuff replace bad. No bad anything then see what you find.

Don't let Ron fool ya. He wasn't doing much looking around. He just sat in the bed of the truck and lectured me and swampdonkey for about an hour. While Swampdonkey and I haggled over what I wanted for a fan clutch.

 

[Floridianson]

Yea got to keep the suspension system tight and right, front and rear never fear.

 

[Jbulach]

Het Simp,
I just realized your U-bolt plates are completely different than my A2, kind of hard to tell by the pictures but it looks like yours may allow more flex

. I wonder if was a revision due to your problem?

 

[Csm Davis]

Het Simp,
I just realized your U-bolt plates are completely different than my A2, kind of hard to tell by the pictures but it looks like yours may allow more flex

. I wonder if was a revision due to your problem?

Ding ding ding! We have a winner! Never have noticed that type mount before. Dude your mounts are not the same as all the rest I have seen. And they don't look like the would stop the problem, you need the newer mounts.

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