ALLEGRO RV 37' pusher rear end noise

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Old 04-10-09, 09:37 PM
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ALLEGRO RV 37' pusher rear end noise

I need help on figuring out how bad of a problem I'm facing. I appreciate any advice...5.9 Cummins with Allison 6
My RV starting out from parked, vibrates some in first gear and when I'm going down the highway and going down the hills or when I take my foot off the pedal, I hear a somewhat of a load what seems to be road noise but I know is not because when I press the excellator, the nosie goes away. This just started coming back home from Florida couple of days ago. Thanks for youor help.
 
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Old 04-11-09, 06:34 AM
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First check the U joints. They would act just like that. Past that point it could a carrier bearing on the drive shaft, then a differential problem, then a transmission problem, then a motor mount.

Over half the time it's the u joints.
 
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Old 04-11-09, 07:01 AM
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Thanks for responding. I'm assuming like other cases, I would be looking for loose joints that have a play. Where is the carrier bearing?
 
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Old 04-11-09, 11:18 AM
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For the u joints: Block your tires to prevent rolling, take it out of gear with emergency brake off (some have the drum on the drive shaft). Then go to each ujoint, hold one side and twist the other side. Any play in the ujoint would require replacement.

The carrier bearing (if you have one - some shorter drive shafts won't) is on the drive shaft to support it along its run to the differential.
 
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Old 04-11-09, 11:55 AM
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Thanks again. I'll see where I can get with this. It's a pretty big(diameter) drive shaft but short. It seems it will take a lot of force to twist it.
Some of the repair shops are unbeleiveable. Just recently they charged me 5 labor hours to change a brake calliper for me on just the front driver side. If I had the tools, I think it would be 1 hour max including the bleeding the brakes...
I can't imagine what they would charge for something major.
 
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Old 04-11-09, 01:48 PM
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Short driveshafts with a good dogleg are candidates for taking out ujoints.

If you change them, make sure you get those with the grease zerk.
 
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Old 04-11-09, 04:54 PM
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Do you know how much I should torque the retaining bolts that hold the U-joint? Also, If I get two new ones, do I have to balance the drive shaft after?
PS; I do plan to marke the drive shaft before I take it out and install it the same way but was not sure if new joints made a difference. thanks
 
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Old 04-11-09, 05:39 PM
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The torque on the half clip bolts would depend on the size of the bolts and that would depend on the chassis that was used in that camper. You could get that information from a Chevy, Ford, or whatever make of chassis it is.

The ujoints are balanced within themselves = no balancing the drive shaft. A drive shaft typically has a balancing weight on it, independent of the ujoints. Marking things of that type is always a good idea for reinstalling it, but in your case it shouldn't matter.
 
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Old 04-12-09, 07:24 AM
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After jacking up the rig and looking at it more closely, I see what my problem is and actually can't beleive it. My rear suspension although it has leaf springs but it has this failry large tube bar that goes from the front of the back axcell to the back of it and has these what seems to be large layered rubber dampers that stack three up and the shock attaches to it.
I see that the bottom stack(rubber) on both sides of the rig has come apart(it looks like ripped apart) that's why the rear sits approx 4 inches lower and this also creates a sever angle for the drive shaft and that explains the noise I have been hearing. Have you seen this type of suspension? do youo know if I have to change the entire unit or does it come in parts? it looks very weak for a rig this heavy to rely on rubber dampers in my opinion. thanks
 
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Old 04-12-09, 07:40 AM
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I'm not familiar with that type of suspension. It's not something used in heavy trucks and is probably specific to the camper industry. Something like that could have been added at the camper manufacturer.

Without seeing a picture of it I couldn't offer an explanation of its purpose - it could be a vibration damping device or it could be for a clearance issue.

As far as replacement parts I suspect you would have to go to the camper manufacturer rather than the chassis manufacturer.

Sorry I can't offer any first hand information on it.
 
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Old 04-12-09, 09:52 AM
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I did a bit of googling and think this kind of suspension is called Hendrickson Block Rubber Suspension. I'll call the frieghtliner counter tomorrow and see what they know about this.
Thankk youo for your help.
 
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Old 04-12-09, 11:36 AM
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There is a Hendrickson suspension used on some grain wagons on rear tandems. That has a center block of rubber for the pivot/attaching point, then a long rocker from the front axle to the rear. The block of rubber sits vertical. It's amazing - the block of rubber is bonded to the metal mounting plates. The rubber supports all the weight.

That suspension is certainly durable for heavy loads.
 
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Old 04-12-09, 06:50 PM
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Yes. That's what I got and the block closest to the back has come apart on both ends of the Axel. Other than the name, I can't find any info or where to call for parts. the hendrickson website does not have it listed as one of their product.
 
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