Truck porpoising when towing..

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  #1  
Old 09-18-16, 08:51 PM
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Truck porpoising when towing..

So I got a newer truck. 2006 silverado 1500 5.3 ext cab LB. 80 k miles.

Old truck was s10 zr2.

Trailer 4500 lb dual axle coachmen 24 ft. 420 lbs TW

My old truck towed the camper fine but of course had lack of power. The WD hitch was set up fine and for the s10 took off 80 lbs off the s10 rear.

Now I set up the WD the same on the silverado. It tows great but side road bumps maks the truck porpoise up and down.

From what I read.

1. Shocks.

S10 has bilsteins from the factory. Truck has 165K miles on it.
Silvy has z85 trailer/towing RPO code. From what I read its just 36mm shock upgrade.

Can shocks be the issue? It is a long bed. I jumpsed up and down on the back bumper and it feels stiff. But when I push down on the front corner I can get that whole truck rocking. It osculates a good 4-5 times before it stops.

2. Read the factory GM receiver round tube with partial bumper mount can be a cause? Not sure why as it still mounts to the frame also.

3. Not enough TW? Maybe I dont need the WD bars engaged. I engage them for the sway control but the silvy probably dont need it. It was mentioned not enough TW so I dont know. I guess Ill go out and tow the trailer around tomorrow with no WD and see what happens.

You would think the opposite would fix it and I should crank the bars up. But I tried that on my s 10 and the back wheels were so light I was able to spin them in gravel like the truck was floating.

4. Tires? Good year wrangler HP's. I am not sure if the are LT's or not. Ill be putting LT's on when these wear, but I probably have 50K miles to go before that.

I have them aired to 35 psi. 44 psi is max. 265-70-17

I cant think of anything else..
 
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Old 09-19-16, 04:20 AM
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What you suggest may work, but I am inclined to think you may need heavier duty shocks for the rear.
 
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Old 09-19-16, 04:50 AM
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I agree, it sounds like the rear suspension is too soft.

But when I push down on the front corner I can get that whole truck rocking. It osculates a good 4-5 times
That would incline me to replace the front shocks as well.
 
  #4  
Old 09-19-16, 05:42 AM
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165 K miles is way past your shock absorber service life.

Replace all four shocks and run your vehicle tires at maximum inflation pressure.
Also make sure the camper tires are also at maximum pressure.

Another thing you could consider is a set of air bag suspension lifts for the rear of the truck.
 
  #5  
Old 09-19-16, 07:15 AM
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I installed a set of coil over shocks to the rear on my Silverado and it made a world of difference.
100% the hitch lines up with the ball?
To high or to low and the tires on the trailer will have uneven pressure.
No way would I be running my tire pressure that low on the truck.
 
  #6  
Old 09-19-16, 01:56 PM
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165 K miles is way past your shock absorber service life.

Replace all four shocks and run your vehicle tires at maximum inflation pressure.
Also make sure the camper tires are also at maximum pressure.

Another thing you could consider is a set of air bag suspension lifts for the rear of the truck.
165K miles is on my s10. I dont drive it anymore and its for sale. The s10 has bilsteins from the factory and towns camper well witout porpoising.

Newer truck is 2006 silverado. long bed. 80k miles and stock 36 mm shocks.. When I tow the same trailer as my s 10 did it porpoises over certain roads and bumps.

Its like the truck is a see saw...

I guess Ill drop the 280 bucks on bilstein 4600's..

Not a fan of ranchos.

Im thinking it may be more the front shocks ... But not sure. why I asked here...
 
  #7  
Old 09-22-16, 05:14 PM
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well Bilsteinns are on.. Big difference.. Ill try the trailer this weekend, but truck alone there is no more floating front end..

I thought the bilsteins would be stiff but they actually ride nice..

I probably would even prefer a firmer shock...

Ill post back after the trailer pull saturday...

Note the other shocks were still good but weak. Plus only 36mm. Bilsteins are 46mm..

Oh what a job getting the fronts off too... Not a job I want to repeat.


I installed a set of coil over shocks to the rear on my Silverado and it made a world of difference.
I wonder if they make them for the front... But I have torsion bars anyway so maybe I can crank them up..

Too late now really as im not spending anymore money for a while on truck upgrades.. ..
 
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Old 09-24-16, 01:32 PM
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Well it was the shocks.. Amazing that the OEM shocks were shot @ only 78k miles..

Truck and trailer ride straight and true now..

Feel sad to sell old red, but shes tired..
 
  #9  
Old 09-24-16, 01:41 PM
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Having trouble posing pics...



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  #10  
Old 09-24-16, 05:51 PM
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Thanks Lawrosa..... I was curious of the fix.
 
  #11  
Old 09-24-16, 06:09 PM
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[IMG][/IMG]

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Had trans gauge added..

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New rear cover on G80

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Im going to miss old red... Hope I can even sell her..

[IMG][/IMG]
 
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