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Clunk from rear when climbing hills


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I've noticed a loud clunk that is heard and felt from the rear of the coach.  It's intermittent and rare but when it does happen it seems to be when climbing a hill and you let off then go back on the throttle.  I don't think it's a hard shift...I'm well versed in the Allison hard shifts!  Maybe more like a driveline issue or something in the suspension loading up then slamming?

Has anyone experienced anything like this with the Roadmaster Chassis?  2004 Windsor 40PKD with 16,000 miles.

 

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Have you checked the u-joints on both ends of the driveshaft?  They sometimes get overlooked when greasing the chassis.  Some of them have 2 zerks, so be sure to grease both if your u-joints have 2.  If they haven't been maintained regularly, the grease might have gotten hard and you might only be getting fresh grease into one or two of the 4 cups.  In that case, I would recommend removing  the, driveshaft and u-joints.  Take them apart and thoroughly clean them before filling them with fresh grease.  Be careful not to lose any of the needle bearings.  Of course you could just buy two new ones and install them.

Carey

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I agree with Ray, broken welds can be a potential source for the sound.  You might also check bushings. 

If you are not capable of crawling under the rig with a good light I'd take it somewhere and have them inspect. 

I've been seeing more and more of these posts then show cracks in welds on the main axle supports or trailing arms.  I do my own maintenance and every time I'm under my coach I drag a shop light underneath and closely inspect the main supports and anything else I can see.  If a problem is caught soon enough it is much easier to repair then if there is a complete failure. 

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Could be the U joints. Only 16,000 miles. Have they been ever greased. When I bought my motorhome in Indiana we drove straight home to CA. When I went to grease it the u joints would not take grease at all. When I pulled them out they had something other than grease in them. Hard and stiff. Surprised we got home, Just replaced them. Although u joints make a pretty constant vibration if going bad. Would really check mountings on rear axle.

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27 minutes ago, Oregon04Windsor said:

Thanks for the input, I'll take a closer look this week.  I have lubed the shaft and joints.  It's so intermittent and that's what makes it annoying.  I've tried to replicate but can't do it at will.  

Busted shock mount?? I think it's a structural issue. U joint would be constant and the vibration would be horrendous.

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I was getting a hard shift in my 2000 Dynasty, cruise control and jake brake do not work well with each other in up and down rolling hills. When approaching up and downgrades try turning either the cruise off OR the Jake brake. 

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As several other highly regarded posters mentioned, check your rear support uprights.  They are generally 3" square tubing.  Initially, cracks may be hard to see, but if you don't have "buttress" plates welded onto your main frame rails, you will want to add them, EVEN IF THAT IS NOT THE REASON for your noise.  They are a well-known failure item.  Although no facility in the country probably has more experience dealing with correcting this problem than Josam's in Orlando, FL, there are no doubt countless heavy-duty truck shops (and even more talented "amateurs") who can deal with this problem.

Dave Pratt, our founder, has had intimate knowledge of repairing this failure.  Hopefully, he will chime in...even though he is a traitor and is one of the SOB group. 😄

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Crawled under tonight for a cursory look and didn't see anything obvious.  Naturally I'll do a full inspection when it's not 30 degrees out.  

I did have a thought:  I was towing our Chevy Tracker and I wonder if what I heard and felt was the tow car taking up slack then pulling back hard when I got on the throttle?

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8 hours ago, Oregon04Windsor said:

Thanks for the input, I'll take a closer look this week.  I have lubed the shaft and joints.  It's so intermittent and that's what makes it annoying.  I've tried to replicate but can't do it at will.  

When you say shaft, do you mean the slip joint on the drive shaft? Is the Windsor the Monaco version of the Holiday Rambler Endeavor?

Gary 05 AMB DST

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I gave the rear chassis a thorough going over today and I'm happy to report there's no cracked welds, broken mounts or broken shocks.  The trailing arms are in excelletn condition too.  I gave the driveline a thorough lubing and we will keep an eye on it.  I'm really hoping it was just the tow car slamming around back there.

 

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10 hours ago, Oregon04Windsor said:

I'm really hoping it was just the tow car slamming around back there

That's a reasonable next area to suspect, but you may want to look further into the towbar & base plate especially where it bolts to the car.  There have been cases where the base plate becomes loose, some even becoming completely detached. Better hope those safety cables hold if that happens, but the cables are attached to the base plate, that's what just came detached from the car, Hum.

You would think if the drive line ( u joints etc ) were worn / loose enough to make a clunk that you would be able to feel the looseness when under the coach, but I certainly can't say that's the case.  As Chuck stated a dropped drive shaft can dig into the road causing extensive damage.  That actually happened to a past memebr.

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Good points Ray and Chuck.  I did give the tow bar a cursory check but I'll go through and tighten everything up there as needed.  I did order new u-joints for the drivelines as a precautionary measure and will install before our next voyage.

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