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Old 06-08-2019, 06:27 PM   #1
mister.freeze
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'71 trailing arm questions

I have a '71 longbed that was made into a trailer. From the get-go, it was bouncy as a trampoline. I put some Monroe Gas Magnum shocks off a Suburban on, thinking the heavier truck had stiffer shocks. They weren't any better. Could have been bad to begin with as the Suburban was just sitting around. My Blazer has a 3/4 ton suspension kit on it, and when I replaced the Pro Comp shocks on it with Bilstien's I warrantied out the Pro Comps and put a new pair on the trailer. Still just a bouncy house on wheels. What gives? The original coil springs are on there, is that the problem? I wouldn't think so. Is it just too light? I wouldn't think that would be the problem either. Thoughts? Thanks in advance.
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Old 06-08-2019, 07:19 PM   #2
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Re: '71 trailing arm questions

Does it trail straight ? I would load a few hundred lbs in it as far forward as possible and see how it acts ? Are the tires balanced ? pick a point on each side of the axle and measure to the hitch and see if it measures the same ,Sometime home built trailers can be a little off center and wander
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Old 06-08-2019, 08:32 PM   #3
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Re: '71 trailing arm questions

It pulls and tracks just fine. The problem is when crawling around inside it or loading it. It's like it has no shocks at all!
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Old 06-08-2019, 09:34 PM   #4
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Re: '71 trailing arm questions

My truck was the same way (coil springs) even with new shocks. It didn't get better until I did the shock relocation kit. Now it's like a modern truck . The relocation kit has the shocks shooting toward the back, rather than the center of the truck. Much better geometry. No more bouncy-bouncy...
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Old 06-10-2019, 11:32 AM   #5
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Re: '71 trailing arm questions

surely these things didn't bounce like that new. Is it a spring problem more than a shock problem? Is there a 3/4 ton coil spring?
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Old 06-10-2019, 03:29 PM   #6
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Re: '71 trailing arm questions

It’s still a weight problem too. With no added weight, it’s always going to be bouncy
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Old 06-10-2019, 04:24 PM   #7
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Re: '71 trailing arm questions

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Originally Posted by mister.freeze View Post
surely these things didn't bounce like that new. Is it a spring problem more than a shock problem? Is there a 3/4 ton coil spring?
Now that you mention it, I did a spring replacement when I did the shock relocation kit, so I don't know if it was the shock relocation or the new springs that fixed it. My original springs were 3/4 ton springs that were horrendously worn out from the owner hauling literally TONS of material in the bed over the years, so it could have been that they were worn out.

I agree with others that it will tow a lot better if you had a couple of hundred pounds in the back of it.
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Old 06-10-2019, 05:54 PM   #8
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Re: '71 trailing arm questions

I guess I just had more faith in what shocks can do.
Would it be worthwhile to convert to leaf springs?
Could I do both, like the old squarebody HeavyHalf?
Any stock-height springs laying around?
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Old 06-11-2019, 01:38 PM   #9
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Re: '71 trailing arm questions

Quote:
Originally Posted by saxart View Post
My truck was the same way (coil springs) even with new shocks. It didn't get better until I did the shock relocation kit. Now it's like a modern truck . The relocation kit has the shocks shooting toward the back, rather than the center of the truck. Much better geometry. No more bouncy-bouncy...
Hey like 60-62 does from the factory!
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Old 06-12-2019, 07:24 PM   #10
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Re: '71 trailing arm questions

You think it needs the suspension? If it’s like a pogo stick it’s surely got to be a dampening issue
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Old 06-13-2019, 08:24 AM   #11
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Re: '71 trailing arm questions

That was my thinking. I guess there's a big difference in when I'm loading and unloading vs going down the road. I'll have to drag it around and have the kids watch it. Maybe its just bouncing on the big tires when empty. I plan to camp in it and they way it rolls around on the suspension is no good. If anybody swapped out some c20 springs to lower theirs I'd be interested...
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Old 07-27-2019, 03:01 PM   #12
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Re: '71 trailing arm questions

New springs. Much better, and taller! Settles down fster, but stillbouncy. How bad would it be to add limiting straps to add some preload?
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Old 07-27-2019, 03:17 PM   #13
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Re: '71 trailing arm questions

Should this be straight?
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Old 07-27-2019, 03:36 PM   #14
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Re: '71 trailing arm questions

Pan hard bar is usually strait, more important are the tires centered in the wheel well?
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Old 07-27-2019, 03:40 PM   #15
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Re: '71 trailing arm questions

Yes, pretty close. Should I try to straighten it? The passenger side is a touch more inboard than the driver side.
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Old 07-27-2019, 10:42 PM   #16
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Re: '71 trailing arm questions

If you really want to cure the bouncy-bounce, do the rear shock relocate. Makes a WORLD of difference.
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Old 07-27-2019, 10:51 PM   #17
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Re: '71 trailing arm questions

Not family with that: is it easy to do?
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Old 07-28-2019, 01:13 PM   #18
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Re: '71 trailing arm questions

Straitened panhard bar will help Center your tire better side to side.....Are those shocks intended to mounted that way, gas shocks can be mounted upside down I think...Oil filled not so much...Look for arrows pointing up?..mounting bracket for shock can be reworked to move the center back an inch or so.
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Old 07-28-2019, 01:41 PM   #19
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Re: '71 trailing arm questions

What springs did you use?
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Old 07-28-2019, 03:14 PM   #20
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Re: '71 trailing arm questions

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Straitened panhard bar will help Center your tire better side to side.....Are those shocks intended to mounted that way, gas shocks can be mounted upside down I think...Oil filled not so much...Look for arrows pointing up?..mounting bracket for shock can be reworked to move the center back an inch or so.
Mounted the shocks that way for clearance, guess I could flip them. Didn't give it much thought.

Which shock mount can be reworked?

Springs came off the front of a Lincoln Navigator. Bottom retainers worked just fine, had to fab the tops. They're 14" long, which is what I thought a C20 spring was, and for a 3/4 ton vehicle.
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Old 07-28-2019, 05:06 PM   #21
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Re: '71 trailing arm questions

well crap. Won't fit the other way around. Not without some "adjustment."

EDIT- A quick call to tech support at Pro Comp said I can mount them either way...
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Old 07-29-2019, 07:54 PM   #22
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Re: '71 trailing arm questions

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Springs came off the front of a Lincoln Navigator. Bottom retainers worked just fine, had to fab the tops. They're 14" long, which is what I thought a C20 spring was, and for a 3/4 ton vehicle.
The springs are not right for what you seem to be doing. They are meant to have the weight of the front of the Navigator on them. The trailer has nowhere near the amount of weight that the front end of a 5,500 lb Navagator has. I would guess that they are so stiff that the tires are actually the suspension. I suggest finding a pair of used 1/2 ton springs and then the trailer should ride much better.
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Old 07-30-2019, 08:26 AM   #23
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Re: '71 trailing arm questions

You're probably right. But they were free and I figured I'd give them a go. I thought about the tire suspension thing too, and I assure you that is not the case. I have a feeling the original springs were just weak from time and maybe somebody trying to lower the truck by heating them. They are not as long as they should have been originally. I decided to try the current springs because of their stiffness. I can push down on the tailgate and it's still a lot softer than it should be. I suspect there just isn't enough preload weight to get the stiffness I want. That's why my question about limiting straps. The ride has improved with the current springs, but still bouncy. Perhaps the swingarm setup is just too independent for my needs. Unfortunately, I have neither the time nor resources to abandon it in favor of leaf springs.
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Old 07-30-2019, 10:41 AM   #24
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Re: '71 trailing arm questions

I don't think the shock mod will help all that much. The rear suspension on a pickup was engineered to have the entire weight factored in how the rear springs work. Obviously the weight bias on a unloaded pickup is heavier in the front...

I am dismantling a LWB trailer I've had too long. It's a bounce house too. The spings have no compression on them
Monroe used to sell shocks with springs on them, might help your deal...if they make them for that pickup...
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Old 07-30-2019, 10:59 AM   #25
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Re: '71 trailing arm questions

adding coilovers to the current setup might work, except for cost and clearance! I'm hoping adding some preload is all I need.
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