Broken Shock Shaft - Causes?

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Broken Shock Shaft - Causes?

Post by Herbie »

Hey all. Interesting to see the new forum format. Hope there's still some folks around.

I was out having fun in the mountains this weekend. I was on a fairly easy Forest Service road, but somewhere along the line I think I gave the rear end of the van a little too much of a thump because it turns out I broke the shaft of a rear Bilstein.

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Shit happens on the trail, and I'm not terribly upset, but I want to make sure I understand the failure mode so that I can hopefully address the issue rather than just throw another shock in there. I *think* maybe I know what happened, but wanted to check with others to be sure.

I believe this is a coming together of too-much weight on the rear, plus a sagging rear lift, plus raised lower shock-mount. I strongly suspect that I just over compressed the rear over a bump and the shock bottomed out.

Specs: My van is currently pretty heavy. I'm right at the rating for the rear axle (3100lbs) and at several points in the last couple of years I've been well over that limit by a few hundred pounds. I'm running the old Overland Vans 4" lift with the 22-687ME springs (S-10, 3/1 leaf, 1350lbs rating), with stock-length shocks with the relocated axle tabs to move the shock-mount. When originally fitted, these springs gave a LOT of rear lift, even with the stock shackles, (currently with lift shackles +1 hole vs. stock), but they've settled (sagged) quite a bit over the last 10 years. (Checks photos, HOLY CRAP I've had this lift kit on the van for 10 years.) From the spring rating alone, you can see I've probably got a problem.

I've previously raised the issue that I think maybe relocating the lower shock-mounts is not a great idea because it changes the geometry such that the bump stops may not do their job. I'm pretty sure this weekend proves me right...

As it happens, I've already got the 22-687HD (4/1 leaf, 1750lb rating) springs sitting in the garage - as I said, I've been aware that the rear of the van is heavy. At the very least, I think I need to get off my ass and fit the heavier springs, but I'm also thinking the whole shock situation needs to be revisited. Anyone got suggestions? Is anyone running the HD springs and have a good shock combo? Thoughts on shock mounting?

Thanks!
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Re: Broken Shock Shaft - Causes?

Post by WoodButcher »

Did you use a taller bump stop when you lifted the van?
I would think as long as your shock absorber travel limits are greater than the axle travel max the geometry wouldn't matter much. It may affect the quality of ride as they wouldn't perform as well but they should not break.

If you lifted the rear 3", the shock mount 3" then the bump stop would need to be 3" taller as well to maintain / limit the suspension travel to stock numbers or you will be hitting the shock limits and they are not made for that.
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Re: Broken Shock Shaft - Causes?

Post by Herbie »

WoodButcher wrote: Mon May 03, 2021 10:03 am Did you use a taller bump stop when you lifted the van?
I didn't. It wasn't on my radar back in 2011. I had some thoughts on the subject a few years later in this thread, but didn't completely follow through:
Herbie @ What's up with my ride quality? (Long)

I even went so far as to fab some bumpstop spacers, but got distracted and didn't install them. Needless to say, they''ll get fitted before I replace the shocks. :D
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Re: Broken Shock Shaft - Causes?

Post by MountainManJoe »

maybe weak springs + axle wrap.

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Re: Broken Shock Shaft - Causes?

Post by Astrophysics »

Hi Herbie,

I put Monroe coil over rear shocks on my 2003 AWD Astro .
I have Bilstein on front.


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Re: Broken Shock Shaft - Causes?

Post by WoodButcher »

Herbie wrote: Mon May 03, 2021 12:46 pm

I didn't. It wasn't on my radar back in 2011. I had some thoughts on the subject a few years later in this thread, but didn't completely follow through:
Herbie @ What's up with my ride quality? (Long)

I even went so far as to fab some bumpstop spacers, but got distracted and didn't install them. Needless to say, they''ll get fitted before I replace the shocks. :D
I would say we're on the same page but you read and skipped over that chapter, lol.
Like Joe mentioned, weak springs, axle wrap certainly would contribute. Not to mention bump stops and the fact your shock ain't new.
You said Bilstiens? I think they are lifetime warranty, check that out. Looking at my rear end makes me think that by moving the shock mount you aren't changing the geometry a whole lot, they should behave like stock IMO. Except for bottoming out w/o the bump stop they are pretty much the same.
'93 Safari shorty, 350 swap
'05 Astro AWD, lifted, 6 liter, cammed, ported and programmed for fast.
'69 G10, straight 6, 3 onatree, jumped at me when I had a pocketful of cash looking for a spare astro. :)
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Re: Broken Shock Shaft - Causes?

Post by Herbie »

OK, here's a follow up:

Anyone know the part number for the upper shock mounting bolt? (Passenger-side, if it matters).

I'm talking about the one that mounts to the "rail" of the unibody. Mine got bent during whatever event broke the shaft of the shock...

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Re: Broken Shock Shaft - Causes?

Post by MountainManJoe »

just hammer it straight again :muhaha:
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Re: Broken Shock Shaft - Causes?

Post by MountainManJoe »

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Re: Broken Shock Shaft - Causes?

Post by Herbie »

AWESOME!

Nicely done - I tried all my usual GM parts places and their diagrams didn't go to that detail. Definitely bookmarking that one.

The bad news is that part looks to be long-since discontinued. Pick-a-part here I come. (Or whack it with the BFH, as you say.)
"My minivan is cooler than your bro-truck"
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1995 Safari GTRV Organ donor - gutted and gone.
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Re: Broken Shock Shaft - Causes?

Post by Herbie »

It took longer to drive to the yard than it did to find and pull the bolts from another Astro, but at least the yard let me have everything for only the entry fee.

I'm set to start my repair/upgrade this weekend.
"My minivan is cooler than your bro-truck"
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1995 Safari GTRV Organ donor - gutted and gone.
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Re: Broken Shock Shaft - Causes?

Post by Herbie »

Well, I'm nearly there. Spent Saturday switching over to the 22-687HD springs I should have been running for years anyhow. Maybe it's the stiffer springs, my sloped driveway, or the fact that I'm getting old, but that job seemed a lot harder than the last time! \:D/

I need nut-and-bolt everything, then I'll be able to get it on a flat surface (NOT my driveway) and actually get decent measurements to order replacement shocks.

At that time, I will also go through my options for bump-stop upgrades to see how much taller I can/should make them. I have two options: I have a set of Energy Suspension stops and some 3" riser pucks (very much like what JOR used to sell), and I also fabbed up a pair of rectangular steel tube spacers with a blind nut, so I can just space the OEM bumpstop up. I kinda like the idea of that better, since the OEM bumpstops are a little more progressive than the short/hard Energy Suspension stop.
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1995 Safari GTRV Organ donor - gutted and gone.
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Re: Broken Shock Shaft - Causes?

Post by WoodButcher »

Lol, I know exactly how you feel.
I recently swapped my fiber springs in the '93 for steel and put in a Detroit tru-trac w/ 11" drums.
In '95 I put a rear in my old '87 g-10 it took me about half the day,
somewhere around '06 I did the rear and a franken-pack in my '97 safari in a day and rebuilt the brakes and axle seals while I was there.
The '93 took me 2 1/2 days!!!
'93 Safari shorty, 350 swap
'05 Astro AWD, lifted, 6 liter, cammed, ported and programmed for fast.
'69 G10, straight 6, 3 onatree, jumped at me when I had a pocketful of cash looking for a spare astro. :)
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Re: Broken Shock Shaft - Causes?

Post by Herbie »

Here's a weird follow up: Anyone ever have trouble with the exhaust fouling on the rear leaf spring?

While I was doing some quick measurements for the bump stops, I realized the end of the exhaust piping after the muffler is hitting the rebound clip on the new leaf spring. I think even if the clip wasn't in that exact spot, the exhaust might rub on the leaf.

I didn't think things were in THAT different a position, but I don't recall the exhaust and older/sagged leaf interfering. Not sure how to remedy that short of having an exhaust shop bend or cut/weld that last section...

EDIT: Additional searching reveals that, Yes, this is "a thing". Great, another item for the punch list.
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Re: Broken Shock Shaft - Causes?

Post by MountainManJoe »

Herbie wrote: Wed May 19, 2021 3:13 pm Here's a weird follow up: Anyone ever have trouble with the exhaust fouling on the rear leaf spring?
I had that issue when I lifted my Astro (new HD leaf spring pack from Overland). It was shaking the whole van when stopped at red lights.

I stopped at a Midas shop on my way from work and pointed it out. The manager there flew my van up the lift, put a torch on the bend in the tailpipe , grabbed the end with his hand and pulled it down until it no longer touched. Had me out the door in about 10 minutes. Didn't charge me a dime.
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