Update 5/2/21 - Bounce and Porpoising - Especially Towing

[corvette744]

Without having looked it up - where do the airbags go with the leaf springs In back? Had previously considered on my 1/2 ton but those went inside the rear springs. Thanks for the input.

I have seen them mounted 2 diff ways either on top of your rear spring and into predrilled holes in your frame,or directly over your axle housing.

 

[George B]

I am no towing expert but I have been following this to learn. A few questions came to mind:

1. If towing with a half ton truck produced better results why look at adding more load capacity to a 3/4 ton?
2. Is the bounce due to excessive suspension travel or do you mean the ride is "harsh" and the rebound is faster than the 1/2 ton.
3. What if you don't use the load leveling hitch or reduce the tension on it?
4. What about tires and pressures compared between the 1/2 and 3/4 ton trucks? It's not apples to apples.

Just thinking...

 

[norcalboon]

I am no towing expert but I have been following this to learn. A few questions came to mind:

1. If towing with a half ton truck produced better results why look at adding more load capacity to a 3/4 ton?
2. Is the bounce due to excessive suspension travel or do you mean the ride is "harsh" and the rebound is faster than the 1/2 ton.
3. What if you don't use the load leveling hitch or reduce the tension on it?
4. What about tires and pressures compared between the 1/2 and 3/4 ton trucks? It's not apples to apples.

Just thinking...

Great questions George, happy to answer because I'm trying to get this figured out myself. I probably should have mentioned it's not a new trailer - I've towed it with my 1/2 tons over 7,000 miles the last 4 years with no issues other than under power with the 5.3L/3.42 combo on my previous 2005 - the 2012 Denali pulls it fine. I wanted to get this rig to last the next 10-15 years that my family will be camping until the kids are grown and not wear out the Denali because we love that vehicle too, but it's my wife's DD, and I just wanted my own

1. Not looking to add load capacity, added the Timbren's to try and soften the bounce, but it turns out they are too big so they may be contributing. Timbren is sending shorter versions at no cost (their support has been terrific BTW). Frankly I'm surprised that a vehicle with a 9400lb stock towing capacity needs anything to be honest, and the rear shocks are new. It was thoroughly inspected with significant maintenance performed at the GM dealer where I purchased it - and again when the water pump went out I had a different dealer inspect it and both did not note that the front shocks needed replacement, but I'm doing it since anyway the rears were shot. It only had 91K miles (now 93K).
2. Both right now, harsher I expected due to the stiffer suspension, but it's an uncomfortable ride and bumps in the road cause it to bounce a few times, and when loaded with the trailer it becomes worse - that when I get the porpoising effect.
3. I haven't tried pulling without WDH, but I've adjusted it to where it is BARELY distributing anything (likewise I've also tried cranking it up to distribute more up front). Hardly any difference in ride quality between those scenarios.
4. I did upsize the tires to 265/70/16 (vs. 245/70/16) and run General Grabber ATS load E inflated to 72 psi rear and 50 psi front. The Denali has Michelin 275/55/20 load D, the previous '05 had Cooper load E at 80 psi rear, forget the exact size. I'll reduce the rear more and see how that feels.

I'm surmising that my front shocks are bad and therefore do not dampen the rebound, and the longer than should be Timbren's are exacerbating that effect currently adding extra rebound in the rear. I saw someone post that they put Bilstein 4600 all around on their GMT 900 and it solved the same issue. So once the front shocks are in I'm hopeful that takes care of it. I mentioned the GM shock part number just to see if anyone else had poor performance from them - seems silly to replace brand new rear shocks that are made for this vehicle that's why I'm only doing the front right now.

Keep the idea flowing I really appreciate the input from everybody!

 

[fasteddy]

LOL....That 5.3/3.42 combo must have been crying it eyes out going up grades with a 28ft trailer.

Every tow vehicle needs needs to be tuned to the application.
Keep working on it....I'm sure you'll get there.
You should be towing in comfort, not getting bounced around.

One thing I do pay attention to is "loaded" weight centered OVER the trailer axles....as much as possible.
I don't know if that is a toy hauler or not.
Do you have a rock buggy, quads, motorcycles or heavy stuff in the back?

Since the 1500s towed it "in comfort" it sounds like you have a tow vehicle issue...So keep working on it.
Because that Yukon XL 2500 with 6.0 / 4.10 is a BadAss tow vehicle....and in the snow? OMG its a tractor especially with chains.
I am so missing mine now.

I don't know how much you paid for it, but out west here, clean 02-06 2500/6.0 subs with < 100K mileage are fetching like $15K-$20K.
I see contractors using them for their work trucks, just pop out the rear seats and you have a secured, enclosed long bed.

 

[norcalboon]

LOL....That 5.3/3.42 combo must have been crying it eyes out going up grades with a 28ft trailer.

Every tow vehicle needs needs to be tuned to the application.
Keep working on it....I'm sure you'll get there.
You should be towing in comfort, not getting bounced around.

One thing I do pay attention to is "loaded" weight centered OVER the trailer axles....as much as possible.
I don't know if that is a toy hauler or not.
Do you have a rock buggy, quads, motorcycles or heavy stuff in the back?

Since the 1500s towed it "in comfort" it sounds like you have a tow vehicle issue...So keep working on it.
Because that Yukon XL 2500 with 6.0 / 4.10 is a BadAss tow vehicle....and in the snow? OMG its a tractor especially with chains.
I am so missing mine now.

I don't know how much you paid for it, but out west here, clean 02-06 2500/6.0 subs with < 100K mileage are fetching like $15K-$20K.
I see contractors using them for their work trucks, just pop out the rear seats and you have a secured, enclosed long bed.

Appreciate it - my thoughts exactly and precisely why I bought it. Had been looking for about a year. Wanted something I can keep for the next couple decades. Wife approved The trailer is not a toy hauler, dry weight 5,500 and scale verified 6,420 loaded. Yes, the 5.3L did not like hills, but towed in flat lands just fine.

Paid $9K out the door from a SoCal dealer who took in on trade and was going to send it to auction, caught it before they did and worked out a deal. Also negotiated below maintenance for $3K and then about $2K for tires/tow mirrors/Timbrens/floor mats/fog lights, and a new water pump so I'm all in about $14K but expect minimal maintenance going forward. Almost all engine seals done, including new oil pan/gasket, valve cover gaskets, timing cover gasket, differential seal, new oil and transmission lines, new radiator and hoses/connections, new rear shocks, new cluster, new MAF, new windshield, new wiper blades, new exterior bulbs as needed, new driver side window switch, air filter, all fluids (brakes, transmission, coolant (obviously), power steering, differential), new airbag module and sensors.

Will do plugs and wires next but not in a hurry, runs great.

 

[avalonandl]

The airbags go on the axle with the help of a bracket right above the LeaF springs. I had good luck with them. Do you have something heavy on the front of the trailer?

 

[Bill 1960]

Timbren is essentially riding on a bump stop. Not what I’d associate with an improved ride. I don’t see any need, considering you’ve towed this with better results using 1500’s.

It sounds like you’ve been sampling different hitch settings, but it’s not best approached by trial and error.

Get the tongue weight right 12-15% (measured not estimated).
Set the hitch head so the trailer is level at tow vehicle loaded ride height.
Set the bars to maintain the same front suspension height on the tow vehicle when towing as it sits not towing (some vehicles will vary on this, go by what your manual says).

 

[livingez_123]

On thing you need to remember is the ½ tons use coil springs and the ¾ ton use leaf springs. They tow totally different. I pulled my Cadillac SRX4 on a u-haul trailer and my 99 ¾t rode great.
What kid of tire pressure are you running in the rear tires? 20in wheels or 17in? Does the trailer sway side to side at all? I would run an adjustable Rancho shock in the rear, that way you can change the rebound and air bags might help.

 

[fasteddy]

The airbags go on the axle with the help of a bracket right above the LeaF springs. I had good luck with them. Do you have something heavy on the front of the trailer? View attachment 277369

Look at that boat just dwarf that avalanche and not even sagging, even looks jacked up.
What's that weight like 7Klbs + and then a 2K trailer?
Nice drives.....


He's got a rock buggy in there, I betcha.

 

[avalonandl]

The boat and trailer weighed 10,800 and avalanche was rated for 12k. It was the 2500 w a 8.1 and 410 axls. Trailered well.

 

[adventurenali92]

Reading through this thread I’m so jealous that I’m only rolling in a half ton Denali, especially for my towing requirements. Lol. I would love to be able to tow with a 2500 XL.

 

[fasteddy]

Reading through this thread I’m so jealous that I’m only rolling in a half ton Denali, especially for my towing requirements. Lol. I would love to be able to tow with a 2500 XL.

Bro,
You have the right ride....6.0L and don't denalis have auto-leveling.

I bought this sub a few years back to go on Jet-Ski camping trips (where they don't have hotels).
6.2, 10spd and it hauls butt.
Its only a 1/2 ton but it has auto leveling and when I realized it could easily tow my 25ft trailer with another car in it (about 8Klbs) I sold
the 2500 RAM cummins, which just sat around waiting for a tow job. I sheet you not, the sub tows just as good as the RAM did
Gets a little worse gas mileage when towing (10 vs 13), but when not towing it gets like 27mpg on the highway. GM-techno-magic.



I ripped the seats out and slid in a queen so I can cool down and sleep back there.
I'd rather camp with A/C and Bose than pitch a tent...especially when its 95 at night.



And I fit this bubble insulation stuff from Home Depot in the windows for cooling and privacy.
It works really good....except I don't have bug screens (to crack the windows)....still have to figure that one out.


But its only a 1/2 ton and it tows really well.

 

[adventurenali92]

Bro,
You have the right ride....6.0L and don't denalis have auto-leveling.

I bought this sub a few years back to go on Jet-Ski camping trips (where they don't have hotels).
6.2, 10spd and it hauls butt.
Its only a 1/2 ton but it has auto leveling and when I realized it could easily tow my 25ft trailer with another car in it (about 8Klbs) I sold
the 2500 RAM cummins, which just sat around waiting for a tow job. I sheet you not, the sub tows just as good as the RAM did
Gets a little worse gas mileage when towing (10 vs 13), but when not towing it gets like 27mpg on the highway. GM-techno-magic.

View attachment 277556

I ripped the seats out and slid in a queen so I can cool down and sleep back there.
I'd rather camp with A/C and Bose than pitch a tent...especially when its 95 at night.

View attachment 277557

And I fit this bubble insulation stuff from Home Depot in the windows for cooling and privacy.
It works really good....except I don't have bug screens (to crack the windows)....still have to figure that one out.
View attachment 277558

But its only a 1/2 ton and it tows really well.

Oh I know my Denali tows well. Lol. I pull a 4300lb sea ray speed boat up and down the mountain for a close family friend. My Denali is an NBS though with a 6.0 and a 4L65E trans. Wish I had a 6 speed.... but it’s ok. I have the factory Z55 air suspension. I’ve replaced arnott shocks and they work quite well. I did add airlift 1000 air bags in my rear coil springs for added stability and leveling. Best mod ever. My one complaint is that going up the mountain I’m not winning any races. Lol. Granted I’m not trying to haul ass, but i wish it had just a little more get up and go umph when it comes to going up the mountain. Although I read up above the OP has the same 6.0 in his 2500 but he has 4.10s and he said he really likes that combo. I may look into re-gearing, purely for the sake of towing, for this year. That may help with the grades and the mountain parts of my towing.
Here’s my towing set up:

 

[fasteddy]

Oh I know my Denali tows well. Lol. I pull a 4300lb sea ray speed boat up and down the mountain for a close family friend. My Denali is an NBS though with a 6.0 and a 4L65E trans. Wish I had a 6 speed.... but it’s ok. I have the factory Z55 air suspension. I’ve replaced arnott shocks and they work quite well. I did add airlift 1000 air bags in my rear coil springs for added stability and leveling. Best mod ever. My one complaint is that going up the mountain I’m not winning any races. Lol. Granted I’m not trying to haul ass, but i wish it had just a little more get up and go umph when it comes to going up the mountain. Although I read up above the OP has the same 6.0 in his 2500 but he has 4.10s and he said he really likes that combo. I may look into re-gearing, purely for the sake of towing, for this year. That may help with the grades and the mountain parts of my towing.
Here’s my towing set up:

View attachment 277597 View attachment 277598 View attachment 277599

Yeah,
I truly wish GM Performance would offer a 10L90E controller that integrates with earlier models.
All they need to do is build an integration box, probably a few months work for them.
The older models would be faster, able to tow more easily, and more fuel efficient, but it would just kill new model sales.
Why would you want a new $85K Tahoe if you could transform a 20 year old one for $6K.

I gotta figure out a way of getting the L86/10L90E into my Tahoe. Or at least that transmission.
I know it can't be don't but that would be so awesome.
My sub just smokes every Raptor to 100mph....wish my Tahoe could do that.

 

[Jeff O]

+1 on tongue weight comment.
I use Bilstein 5100 with reservoirs on my tow rig. Works great with and without the trailer.
Taz

My '03 Tahoe has Nivomat self leveling shocks. Don't know what years this was a factory option. They work great, but I've not tried them to the full GVW. research how they work by Googling. They are not cheap ~$300 each.

 

[Jeff O]

My '03 Tahoe has Nivomat self leveling shocks. Don't know what years this was a factory option. They work great, but I've not tried them to the full GVW. research how they work by Googling. They are not cheap ~$300 each.

Nivomats have also been discussed in prior forum posts. NAPA is one source.

 

[Tshezz]

I have a 05 escalade which I replaced all the shocks and rear springs with a kit from suncore industries. I bought the kit with the helper springs for the rear shocks. Got rid of stock airbags as they were shot and compressor was shot. I am towing around a 30' travel trailer ~6700 empty.

 

[rzabel]

I tow a similar sized trailer with a similar Yukon XL 2500 all over the west, including Canada and Mexico and don't have that problem. I have an EAZ Lift WD hitch and 4600 Bilsteins, but otherwise stock suspension. I run 285/75/16 Michelin LTX and run them at 50 psi front 80 psi rear, just like the door label. I've always been impressed by the ride, but I don't have a half ton to compare it to. I don't really have any suggestions, sounds like you're doing everything right, just providing another data point.

 

[Mr Dan]

LOL....That 5.3/3.42 combo must have been crying it eyes out going up grades with a 28ft trailer.

Every tow vehicle needs needs to be tuned to the application.
Keep working on it....I'm sure you'll get there.
You should be towing in comfort, not getting bounced around.

One thing I do pay attention to is "loaded" weight centered OVER the trailer axles....as much as possible.
I don't know if that is a toy hauler or not.
Do you have a rock buggy, quads, motorcycles or heavy stuff in the back?

Since the 1500s towed it "in comfort" it sounds like you have a tow vehicle issue...So keep working on it.
Because that Yukon XL 2500 with 6.0 / 4.10 is a BadAss tow vehicle....and in the snow? OMG its a tractor especially with chains.
I am so missing mine now.

I don't know how much you paid for it, but out west here, clean 02-06 2500/6.0 subs with < 100K mileage are fetching like $15K-$20K.
I see contractors using them for their work trucks, just pop out the rear seats and you have a secured, enclosed long bed.

 

[Mr Dan]

For sleeping in the back of our NBS we use a lightweight roll of nylon screen and magnetic tape strips. After a little adjusting, instant window screens.