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jeffw

How do you know when shocks are shot?

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We're out for our first trip this weekend and I'm wondering if we need new shocks. The truck has 735k on it and we didn't get any service records with it. We did replace the cab shock absorber and stay rod when we bought it last year.

When we go over really bad bridge joints the cab tends to oscillate a few times before it settles down. 

Thoughts?

Edited by jeffw

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#1: Are they leaking?
#2: You would need to take one end off and check if the still have damping or if there is radial play.

It would be good to know what a new shock feels like before you get the wrenches out

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Since you replaced your cab shocks recently, just get used to the cab rocking a bit.  It's normal.

Did you stay tandem?  If tandem, I would only replace one set of shocks.

If not tandem, you might want to replace that set now if you don't know how old they are.

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Change them!  Shocks do not last long on these "Big Toys"  If you are going to remove one to "check it out" why not change them while you're there.  Replacement OEM shocks are available from various sources and are not very expensive.  New shocks do make a difference in ride quality just dont expect it to ride like your Chevy.  

You also didn't happen to mention if you have an air ride front suspension. If so look at the air bags and the leveling valves for proper operation and ride height.  Suspension bushings may need replacement.  Cab bushings don't last forever. Lots of parts wear on these trucks and are never replaced by the previous owner(s). A big problem with no maintenance records is no "base line" exists to see if parts were ever replaced. 

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Good suggestions...thanks.

We are tandem, and it has air front suspension. Shocks weren't leaking last time I looked...will put eyes on them again. They were Volvos, which makes me wonder.

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If you pull one, change it. Takes big wrenches or a good air wrench (not a harbor freight. Mine was not powerful enough) and I ended up cutting one bolt off with a reciprocating saw because the bottom bolt was seized to the bushing.

 

Brad 

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I would preemptively change them. And it may be time anyway. That way you know what you have, and they are not expensive, and are generally pretty easy to change. If you have front air suspension make sure the bags are functioning properly. You will get some sway int he cab - that is normal. It is hard to say what is excessive from just a description. But I'd change the shocks since they are an unknown and cheap.

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If you don't have to fight rust, figure about $75 each and 5 minutes to replace the front ones with a good impact wrench.  No need to jack it up, take off a wheel, or anything like that--just open the hood.  Just like the shocks on a car, every 100,000 miles or so a new set will make a difference.

If I had a rusty truck, I might be tempted to leave them alone.

Edited by Nuke-E

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2 hours ago, Nuke-E said:

If you don't have to fight rust, figure about $75 each and 5 minutes to replace the front ones with a good impact wrench.  No need to jack it up, take off a wheel, or anything like that--just open the hood.  Just like the shocks on a car, every 100,000 miles or so a new set will make a difference.

Are the rears that easy too?

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On ‎4‎/‎11‎/‎2017 at 11:09 AM, Alie&Jim's Carrilite said:

For the price of a set of Monroe's.... replace them.  

How do you go about buying the correct shock (Monroe or other brand)?  I am guessing my local auto parts store does not have a cross-referenced chart for a Volvo.

Edited by Refuzn-To-Grow-Up

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When I built my off-road truck, I measured what I wanted for the limits of full open, full close, and normal position, and then seached through a couple different web sites and found the shocks I wanted. The measuring was the longest part and the searching was quite easy.  In your case, since you have an existing shock and the ability to get a part #, just see what the specs are for your existing shock and buy one that matches/exceeds.

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7 hours ago, Refuzn-To-Grow-Up said:

How do you go about buying the correct shock (Monroe or other brand)?  I am guessing my local auto parts store does not have a cross-referenced chart for a Volvo.

 
 

Shocks pretty much go by Generation on our trucks.  Class 8 truck parts is great to deal with as well.  Do a search on their website and your part numbers appear.  You can cross reference the part numbers.  Or your local HDT supplier should be able to work off of the last 6 of your VIN number.  NAPA can usually find them.

Edited by Alie&Jim's Carrilite

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8 hours ago, Refuzn-To-Grow-Up said:

How do you go about buying the correct shock (Monroe or other brand)?  I am guessing my local auto parts store does not have a cross-referenced chart for a Volvo.

I haven't looked for shocks specifically, but NAPA does have heavy duty truck listings (on a clunky website), and O'Reilly's has HDTs in their catalog (good website, but probably not as extensive of part offerings).

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The existing shock absorber has a part number on it likely. That number will cross to other manufacturer models that will fit. I wouldn't be afraid to source this at an Amazon or Ebay, as long as the product being purchased is a recognized name brand. 

One of my favorite sources of HD truck parts:  https://www.ryderfleetproducts.com/ryder/

 

 

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34 minutes ago, beyerjf said:

The existing shock absorber has a part number on it likely. That number will cross to other manufacturer models that will fit. I wouldn't be afraid to source this at an Amazon or Ebay, as long as the product being purchased is a recognized name brand. 

One of my favorite sources of HD truck parts:  https://www.ryderfleetproducts.com/ryder/

 

 

Jeff:

I just checked out this website.  Excellent resource.  THANKS!

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Hi Everyone,

I have a question about shocks myself. What shock would work best for are application. Volvo brand, I believe is an oil filled shock or a shock like a Monroe which I believe is a gas shock ?

All opinions welcomed,
Al

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A gas shock still has the conventional oil damping valving, typically 50-50, meaning the valving is set to be equal on extension and compression . Add a compressed gas chamber to the mix and as an example the gas shock will extend all by itself to the top of the travel when uninstalled. All most all shocks available now are gas shocks. Someone out there who has the prerequisite engineering degree can explain why gas shocks are supposed to be superior. 

A video from my favorite program, "How it's Made"

 

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I could be wrong, it was a long time ago when I read a technical article in a motorcycle mag about the latest thing, Gas Shocks........  I believe the word "gas" is used because nitrogen is used in place of air within the shock body.  This is because nitrogen won't aerate the oil as it's forced through the metering orifices.  Foamy oil doesn't do much to dampen the motion.  Some "Gas Shocks" have a remote reservoir to help keep the oil and nitrogen separated.  Mostly seen on high performance applications.

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Don't be scared to check pricing on maintenance parts at your Kenworth or Peterbilt dealer - they sell an all makes line from Paccar Parts called TRP. 

Edited by noteven

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On ‎4‎/‎15‎/‎2017 at 4:52 PM, beyerjf said:

A gas shock still has the conventional oil damping valving, typically 50-50, meaning the valving is set to be equal on extension and compression . Add a compressed gas chamber to the mix and as an example the gas shock will extend all by itself to the top of the travel when uninstalled. All most all shocks available now are gas shocks. Someone out there who has the prerequisite engineering degree can explain why gas shocks are supposed to be superior. 

A video from my favorite program, "How it's Made"

 

Hi Jeff,

Thank you for posting the video. Now I know how shocks are built. I had to idea how they where manufactured.

Al

Edited by alan0043

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13 hours ago, noteven said:

Don't be scared to check pricing on maintenance parts at your Kenworth or Peterbilt dealer - they sell an all makes line from Paccar Parts called TRP. 

The other thing is...if you have a Volvo and there is a Mack dealer near you, it is possible to get the identical Volvo part far cheaper. At least on most things that cross over.

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19 hours ago, beyerjf said:

A gas shock still has the conventional oil damping valving, typically 50-50, meaning the valving is set to be equal on extension and compression . Add a compressed gas chamber to the mix and as an example the gas shock will extend all by itself to the top of the travel when uninstalled. All most all shocks available now are gas shocks. Someone out there who has the prerequisite engineering degree can explain why gas shocks are supposed to be superior. 

A video from my favorite program, "How it's Made"

 

The sole purpose of the gas, is to reduce foaming of the hydraulic fluid within the shock reservoir.  That is what makes them superior to non gas. 

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