Why do tow vehicles "sag" in the rear, under a load they were designed to accommodate
09-02-2015, 04:31 PM
#21
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I want to thank everybody that took the time to add their comments and experiences regarding towing. It helps. So here's a little more info on the my Avalanche 2500 and trailer. By adding another leaf spring to the Avalanche rear suspension as I mentioned in my first post, the height of the hitch was raised in the air app. 6 inches. When the weight of the 9,000 trailer with likely 1000+ pounds is added to the hitch, the hitch goes down maybe 8". When I add the weight distribution bars on the trailer and then lower the trailer weight onto the hitch, I'd say it goes down by only 5-6 inches. The truck and trailer are really leveled out nicely when the weight distribution bars are in place. I have never used the sway control arm that is is part of the Reese weight distribution system. Do they really work?
The front end does get "light" as I said before when going over bumps and highway heaving. I'm sure most of you guys have experienced that heaving at some time or another. It isn't a dangerous amount of heaving, it's more the front end gets lighter for a moment or two and there is a little porpoising effect. I have 2 year old, call them 10K miles old Bilstein HD shocks, on all four corners. They seem to be good shocks. The truck rides pretty much the same unloaded or with the 9,000 lb trailer hitched up. I do NOT have one of those steering arm shocks that you see on off road trucks occasionally. I almost wish the shocks had a little more anti-rebound damping effect so that there would be more resistance to shock absorber "lift" on up motion on the porpoising stroke. Does that make sense?
Many of you suggested air bags as a supplement. It seemed that the consensus is to keep the springs where I'm at, with the 1 spring that I added, because I am getting the tow vehicle and trailer level with the extra spring I put in, and the weight distribution hitch. So naturally, my next question is, does anybody have any recommendations on an air bag system? And I'd like to confirm that we are only talking about a rear bag set up. How difficult is it to install? Should I add a 2nd battery to the tow rig to make sure I am not taxing the primary battery? And beside, I know diesels typically have dual batteries, so why not a gasser with a big tow commitment? So I think I answered my own question on the battery! But if there are some thoughts on air bag systems, and which brands are reliable, and what stores are reputable, such as, I have had great experiences which etrailer.com, I'd appreciate that info.
Yeah, the day will come when I'll have to trade the Avalanche 2500 in for a new tow rig, and I'll likely go diesel at that point in time, because who can resist 750 ft lbs of TQ, and a tranny that can tow a space shuttle, but I really do like the cost efficiency of upgrading something I already own, and not signing up for a new truck payment at this particular time. When I do decide to get a new rig, I'll definitely want to listen to all your points of view and glean some knowledge from you guys.
Again that's for all the comments, and please keep the info coming. I appreciate your advise and help.
The front end does get "light" as I said before when going over bumps and highway heaving. I'm sure most of you guys have experienced that heaving at some time or another. It isn't a dangerous amount of heaving, it's more the front end gets lighter for a moment or two and there is a little porpoising effect. I have 2 year old, call them 10K miles old Bilstein HD shocks, on all four corners. They seem to be good shocks. The truck rides pretty much the same unloaded or with the 9,000 lb trailer hitched up. I do NOT have one of those steering arm shocks that you see on off road trucks occasionally. I almost wish the shocks had a little more anti-rebound damping effect so that there would be more resistance to shock absorber "lift" on up motion on the porpoising stroke. Does that make sense?
Many of you suggested air bags as a supplement. It seemed that the consensus is to keep the springs where I'm at, with the 1 spring that I added, because I am getting the tow vehicle and trailer level with the extra spring I put in, and the weight distribution hitch. So naturally, my next question is, does anybody have any recommendations on an air bag system? And I'd like to confirm that we are only talking about a rear bag set up. How difficult is it to install? Should I add a 2nd battery to the tow rig to make sure I am not taxing the primary battery? And beside, I know diesels typically have dual batteries, so why not a gasser with a big tow commitment? So I think I answered my own question on the battery! But if there are some thoughts on air bag systems, and which brands are reliable, and what stores are reputable, such as, I have had great experiences which etrailer.com, I'd appreciate that info.
Yeah, the day will come when I'll have to trade the Avalanche 2500 in for a new tow rig, and I'll likely go diesel at that point in time, because who can resist 750 ft lbs of TQ, and a tranny that can tow a space shuttle, but I really do like the cost efficiency of upgrading something I already own, and not signing up for a new truck payment at this particular time. When I do decide to get a new rig, I'll definitely want to listen to all your points of view and glean some knowledge from you guys.
Again that's for all the comments, and please keep the info coming. I appreciate your advise and help.
09-02-2015, 05:17 PM
#22
Search some of my old posts.
I too had a 2500 Avalanche, and did a lot upgrades to improve it's towing stability along the lines of:
-airbags
-solid steel rear wheel spacers
-8 & eventually 9+ wide wheels and tires
You can't use the 3rd sway control arm on a trailer that has a Surge Brake System.
Even though my 2500AV was barely rated to tow my 12,000 lbs. load...
...it's night and day difference now towing with a 1-ton diesel dually.
I too had a 2500 Avalanche, and did a lot upgrades to improve it's towing stability along the lines of:
-airbags
-solid steel rear wheel spacers
-8 & eventually 9+ wide wheels and tires
You can't use the 3rd sway control arm on a trailer that has a Surge Brake System.
Even though my 2500AV was barely rated to tow my 12,000 lbs. load...
...it's night and day difference now towing with a 1-ton diesel dually.
09-02-2015, 07:02 PM
#23
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For the win!: http://www.duramaxsuburbans.com/Conversionpricing.html
Not specifically towing related but I have upgraded the steering on my Avalanche 2500 (which will apply to all GM trucks) with some Cognito parts check them out. http://www.cognitomotorsports.com/ch...ring-upgrades/
Also if your front unit bearings ever go out (which they will) use Timkin ones depending on vendor they have a lifetime warranty and they are what seem to last the longest from the research I have done.
You should not need a second battery for any towing you are doing.
Not specifically towing related but I have upgraded the steering on my Avalanche 2500 (which will apply to all GM trucks) with some Cognito parts check them out. http://www.cognitomotorsports.com/ch...ring-upgrades/
Also if your front unit bearings ever go out (which they will) use Timkin ones depending on vendor they have a lifetime warranty and they are what seem to last the longest from the research I have done.
You should not need a second battery for any towing you are doing.
Last edited by Diamond Dave; 09-02-2015 at 07:10 PM.
09-03-2015, 06:30 AM
#24
The new Denali's have the Magnetic fluid shocks and air adjustable shocks for ride height. I have a Yukon Denali towing 6000lbs and with 6 passengers coolers and a full boat it sits the same as empty. The 6.2 LT1 8 speed automatic pulls like a diesel too, can barely tell your pulling 6000lbs when passing. The new oversize brakes are a big improvement as well. FWIW they have a Denali HD, but I would look at the MAX tow package if your looking at Gas, the 6.2 LT1 has great torque.
09-03-2015, 09:24 AM
#25
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Second battery kit is available- but pricey. I used air bags and trailered my Chris cat with no issue. 11k with trailer. I installed Firestones.
Last edited by wannabe; 09-03-2015 at 09:26 AM.
09-03-2015, 11:01 AM
#26
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Firestone airbags are easy to install and reliable. A second battery is not needed, the pump is not a huge draw, if you choose it. You can do the in cab switch with gauge and your able to adjust the bags from your seat, or a cost effective approach is just a Schrader valve with no pump and fill at the bumper. I installed the rear kit with pump on my old Excursion pulling a 27 Baja and then 353 Fastech. I had added a leaf with sway bar before that and it was just not enough. Even after the bags the truck steered "light", replaced the truck with 6.7 F350 CC long bed single wheel and steering is not "light" anymore. I feel the short wheel base had a lot to do with the feel of the steering.
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09-03-2015, 12:41 PM
#28
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I too have a 2500 Avalanche. The biggest thing regarding the rear squat when loaded is the fact that the hitch is a mile behind the rear axle. Measure hitch to axle on a regular pickup and it is much shorter. The springs should help and you could even install a dual shock system on the rear which would help.
As for the light feeling steering, I know where you are coming from. GM never put a steering stabilizer on the 3/4 ton trucks but the mounts and provisions for them are there. Add one in and it will decrease that light feeling a ton as well.
As for me, I am putting my 2500 AV up for sale and just picked up a 2015 Silverado 1500. Interesting to see how well that tows my 7000 lb boat and trailer. I have heard the 15's are heads and shoulders above the old body style 1500's as far as towing is concerned.
As for the light feeling steering, I know where you are coming from. GM never put a steering stabilizer on the 3/4 ton trucks but the mounts and provisions for them are there. Add one in and it will decrease that light feeling a ton as well.
As for me, I am putting my 2500 AV up for sale and just picked up a 2015 Silverado 1500. Interesting to see how well that tows my 7000 lb boat and trailer. I have heard the 15's are heads and shoulders above the old body style 1500's as far as towing is concerned.
09-03-2015, 12:42 PM
#29
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You shouldnt need a weight distributing hitch. You need to get an accurate tongue weight of the trailer. The bulk of the weight should be on the trailers axles. If your front end of the truck is light you have too much tongue weight. Find a truck scale and weigh get your tongue weight by unhitching the truck from the trailer so only the trailer jack is on the scale. Once you have that adjust the boat on the trailer and weigh it again. 5-600 lbs should work and then go road test it. You want just enough tongue weight to keep the hitch from becoming unweighted on a bump but not so much that it lightens the front end. Short wheelbase trucks such as an avalanche are trickier than a crew cab full size because the longer truck is an effectively a longer lever against the tongue weight that is using the rear axles as a fulcrum to lift the front of the truck.
