Auto leveling on tow vehicle...

[ROBERT CROSS]

Some more autoride info


AutoRide is actually 2 separate systems, depending on whether a 1500 or 2500. On the 1500 models, AutoRide uses an onboard compressor with air shocks to help level the rear when under a load. There are procedures in the owners manual for hitching with a weight distributing (WD) hitch on Suburbans that have the AutoRide option. The compressor can be a few hundred $$ to repair if it goes out.

On the 2500 models, AutoRide is a real-time damping (RTD) system, controlled by a separate ride control computer (RCC). Special shocks are used with a ferrous fluid that changes viscosity when an electric current is applied. There is a ride height sensor at each wheel that measures suspension travel, in turn providing input to the RCC that varies the current sent to each shock to stiffen/soften them as needed to optimize the ride. This happens something on the order of 100 times per second. Note that NO leveling function is provided by AutoRide on the 2500.

The AutoRide on the 2500 Suburbans is optional with the 6.0L but was a "mandatory" option with the 8.1L, so ALL 2500 Suburbans with the 8.1L will have AutoRide.

[wannaB]

Hello Everyone. I am considering the purchase of a new AS, so I've been trying to figure out exactly what my truck has on it (a 2004 Avalanche Z66). I can't seem to figure it out even by talking to the guys in the dealerships. When I first bought the truck I noticed a reference to air ride suspension and checked it out. I left with the impression that early Avalanches had true air ride suspensions with air bags and compressors. Mine, on the other hand only had special rear shocks that leveled out after a bit of driving. They were part of the Z66 Premium-Ride Suspension package. More recently, by acquiring a copy of the build sheet for the truck, I found out it has the Z82 trailering suspension to go with the HD trailering package. I now assume that the Premium Ride shocks were replaced by the HD suspension components, but the dealer can't tell me if that's the case. I've e-mailed chevy about it, but no response so far. Any idea how I can sort this out? I'd like to know exactly what I have to work with before I buy the trailer.

[arm4]

Thanks for all of the imput. When the dealer set up the system the key was off in the TV. Both the TV and the AS were level with final adjustment. When I turn on the ignition the auto level runs for just a moment. On my next adventure I will pull the fuse and see what the result is. Great idea HowieE. Again thanks to all.

[moosetags]

We tow a 25FB with an '05 2500 Suburban with Quadrasteer. All Quadrasteer Suburbans are 2500's and have Autoride. We have almost 30,000 miles with this TT/TV combo. We have never noticed any illeffect from the Autoride.

[Inland RV Center, In]

Originally Posted by arm4

I have a chevy avalanche...when I connect the hitch the auto leveling pump engages and levels out the truck. How does this effect the towability of the AS and TV and the weight distributing hitch. Any insight? Thanks, Randy

Based on a 10 year plus study by the old insurance division of Airstream, (2/3) two thirds of all loss of control accidents, were caused by tow vehicle rear end modifications.

That list included, amoung other things, air shocks improperly inflated, air bags improperly inflated, Monroe load levelers, overload springs, and automatic inflation systems.

The automatic inflation system is about the # 1 killer of the purpose of a load equalizing hitch.

It destroys the proper shifting of weight.

Unfortuantely, just because the trailer and tow vehicle are level, is no sign of proper load eqauliziation.

Andy

[ROBERT CROSS]

Originally Posted by ROBERT CROSS

Some more autoride info


AutoRide is actually 2 separate systems, depending on whether a 1500 or 2500. On the 1500 models, AutoRide uses an onboard compressor with air shocks to help level the rear when under a load. There are procedures in the owners manual for hitching with a weight distributing (WD) hitch on Suburbans that have the AutoRide option. The compressor can be a few hundred $$ to repair if it goes out.

On the 2500 models, AutoRide is a real-time damping (RTD) system, controlled by a separate ride control computer (RCC). Special shocks are used with a ferrous fluid that changes viscosity when an electric current is applied. There is a ride height sensor at each wheel that measures suspension travel, in turn providing input to the RCC that varies the current sent to each shock to stiffen/soften them as needed to optimize the ride. This happens something on the order of 100 times per second. Note that NO leveling function is provided by AutoRide on the 2500.

The AutoRide on the 2500 Suburbans is optional with the 6.0L but was a "mandatory" option with the 8.1L, so ALL 2500 Suburbans with the 8.1L will have AutoRide.

NOTE: AUTORIDE DOES NOT= AIR RIDE

MY 06 2500 BURB HAS AUTORIDE BUT NO AIR RIDE

[BillTex]

From GM owners manual;

Level Control

Automatic Level Control

The automatic level control rear suspension is available
on C/K 1500 vehicles and comes as a part of the
Autoride™ suspension, if equipped.
This type of level control is fully automatic and will
provide a better leveled riding position as well as better
handling under a variety of passenger and loading
conditions. An air compressor connected to the rear
shocks will raise or lower the rear of the vehicle
to maintain proper vehicle height. The system is
activated when the ignition key is turned to RUN and
will automatically adjust vehicle height thereafter.
The system may exhaust (lower vehicle height) for
up to ten minutes after the ignition key has been turned
off. You may hear the air compressor operating when
the height is being adjusted.
If a self-equalizing hitch is being used, it is
recommended to allow the shocks to inflate, thereby
leveling the vehicle prior to adjusting the hitch.

Autoride™

If equipped, the Autoride™ feature will provide a
superior vehicle ride and handling under a variety of
passenger and loading conditions.
The system is fully automatic and uses a computer
controller to continuously monitor vehicle speed, wheel
to body position, lift/dive and steering position of the
vehicle. The controller then sends signals to each shock
absorber to independently adjust the damping level to
provide the optimum vehicle ride.
Autoride™ also interacts with the tow/haul switch that,
when engaged, will provide additional control of the
shock absorbers. This additional control results in better
ride and handling characteristics when the vehicle is
loaded or towing a trailer. See

Tow/Haul Mode Light on
page 3-54 for more information.

4-64

[funkill]

As I am researching how to properly adjust my Draw-Tite WD hitch (and considering purchase of additional cam arm/Reese from Hitch-It), I found this thread.

After purchasing my new TV (2000 YukonXL), I spent hours trying to set the hitch. I couldn't seem to get anything to work out right - levelness of rig, front/rear loading, etc. I got frustrated and just left it as best as I could - expecting to readdress it later. Later is moving forward. After reading Andy’s Towing Myths article, I realize I need to move this to parallel priority of getting new TV tires.

So, I noticed BillTex’s entry here on the auto-leveling concern. I retrieved my owner’s manual for the YXL as it has the original window sticker tucked inside. The sticker shows “Self-Leveling Rear Shocks” under standard equipment, no Autoride option. The owner’s manual shows three options:

· Level Control (If Equipped)

o Self-Adjusting --- available on C/K 1500 vehicles and is available with the premium smooth ride suspension package
o Automatic Level Control --- available on C/K 1500 vehicles and part of the Autoride suspension

· Autoride (If Equuipped)

My local GMC dealer verified the build for my VIN has “premium smooth ride suspension with level control, manual, self-adjusting” and no Autoride.

Below is an excerpt from my owner’s manual regarding the unique adjustment for setting equalizing hitches with Self-Adjusting Level Control. My instructions for Automatic Level Control and Autoride are the same as BillTex posted. I’m posting the details below for the third option (of hydraulic shocks) for others, if interested. From page 2-33:

Level Control (If Equipped)
Self-Adjusting
The self-adjusting rear suspension is available on C/K 1500 vehicles and is available with the premium smooth ride suspension package.
This type of level control will provide a leveled riding position as well as improved handling under a variety of passenger and loading conditions. A hydraulic pump inside each rear shock absorber raises the rear of the vehicle to the proper height, based on inputs from the road surface, while the vehicle is being driven. It takes approximately 2 miles (3.2 km) of driving for the leveling to complete, depending on the road surface conditions.
If the loaded vehicle is not moved for approximately twelve hours, the leveling system may bleed down to a lower height. This can be especially apparent is a trailer is left attached to a parked vehicle for long periods of time. The vehicle must be driven to re-level the vehicle.
If a self-equalizing hitch is being used, the vehicle should be driven approximately 2 miles (3.2 km) with the trailer prior to adjusting (leveling) the hitch.

I don’t think I traveled over a mile to where I worked on setting my hitch. And I drove there with the WD hitch/bars engaged. I only recently noticed a high pitched sound from my TV when hooking up --and started to wonder if there is some auto-level device on it! Do you think that the sound I’m hearing is the hydraulic pump in my shocks? I only notice it when I’m hooked to the trailer at the start of my trip. Don’t recall hearing it as I’m unhitching at a CG site…

I guess I need to verify both the rear shocks are operating correctly. Would measuring the wheel well heights at rear and comparing them (left-to-right) be evidence enough?

According to another truck forum, I’ll need to replace them with, “a very high pres. self leveling shock that is about the size of a small tree trunk. If you have this option you can only go back with these units. They are supplied to GM by Sachs and are very, very expensive.” Great, over $300 each at http://www.partsgeek.com/mmparts/shock_absorber/gmc/yukon_xl_1500.html

I called Hitch-It (authorized dealer for DrawTite/Reese) and they verified that I can purchase the dual cams to add to my existing hitch. They also sell the DrawTite round bars in 600, 800 and 1200 lbs. I think I have 800’s. After reading Andy’s Towing Myths article, I wonder if I am okay. He suggested 750 for ½ ton that is not overloaded. Guess the CAT scales will tell!

OH – I found a good presentation for installing and adjusting dual cam hitch on this website: http://store.drawtite.com/wedi.html -- click on Link for tips on installing a
weight distribution setup


Laura – who intended this to be shorter but the details just got away from me.

[wannaB]

Funkill, thanks for doing all that digging. I, too, have the load leveling shocks (2004 Avalanche, Premium Ride) and have had difficulty getting a good read on what to do about it. As many "It'll be OKs" as "No Ways"s. Most people assume it's a conventional load leveling system. I found all of the GM instructions you refer to, but credit Andy R with knowing a thing or two about this and have been skeptical (thanks for all of your contributions, Andy). The old data is probably referring to load-leveling "systems", not just shocks - still.... Andy's article seems to suggest that even if you get everything set up properly, the truck will find a way to foil you over time. Could the simplest solution be to just replace the shocks with non-leveling ones? None of my GM sources would buy into any kind of change to the truck or suggest a specific shock to replace the current ones with. What could be wrong with just using the ones that come with the regular truck? Is there something else to that Premium Ride option that isn't apparent? (Already replaced the factory tires with LT, E load range tires.)

[Inland RV Center, In]

Originally Posted by wannaB

Funkill, thanks for doing all that digging. I, too, have the load leveling shocks (2004 Avalanche, Premium Ride) and have had difficulty getting a good read on what to do about it. As many "It'll be OKs" as "No Ways"s. Most people assume it's a conventional load leveling system. I found all of the GM instructions you refer to, but credit Andy R with knowing a thing or two about this and have been skeptical (thanks for all of your contributions, Andy). The old data is probably referring to load-leveling "systems", not just shocks - still.... Andy's article seems to suggest that even if you get everything set up properly, the truck will find a way to foil you over time. Could the simplest solution be to just replace the shocks with non-leveling ones? None of my GM sources would buy into any kind of change to the truck or suggest a specific shock to replace the current ones with. What could be wrong with just using the ones that come with the regular truck? Is there something else to that Premium Ride option that isn't apparent? (Already replaced the factory tires with LT, E load range tires.)

The basic problem with an automatic leveling system, is that it will continually fight what the load equalizing hitch is trying to do, namely, move weight.

If the system decides to add air, then it also adds weight to the rear end of the tow vehicle, and takes it away from the steering axle. If that added weight to the rear gets high enough, which will vary for each different rig, then loss of control, could happen.

Andy

[HowieE]

Government Motors will never learn.

Back in the 70s they had a leveling system on the Suburbans that changed the braking ratio between the front and rear brakes. When the Suburban was sitting level with a WD hitch, and lots of weight on the rear wheels, the rear brakes were at min.

Most people disconnected the system as soon as they realized they had no rear brakes.

The best thing to do with the load leveling system while towing is disconnect it.

[funkill]

[quote=HowieE;705814]Government Motors will never learn.

Back in the 70s they had a leveling system on the Suburbans that changed the braking ratio between the front and rear brakes. When the Suburban was sitting level with a WD hitch, and lots of weight on the rear wheels, the rear brakes were at min.

Most people disconnected the system as soon as they realized they had no rear brakes.

The best thing to do with the load leveling system while towing is disconnect it.[/quote]


How do you disconnect hydraulic, self leveling shocks while towing?

After reading my manual, it appears as though the addition of an equalizing hitch was understood and a method for adjustment was provided. Since my initial attempt to adjust my WD hitch on this TV were ineffective, I'll see what driving for a few miles before attaching does for it! And my initial thought is that if the shocks were increased, it would apply more load to the steering axle?? I'd think more about that, but I'll probably forget after my meeting in 10 minutes... I'm going to do al little work at the CAT scales soon. I report my findings and notes on how it rides, if the shocks appear to re-adjust (maybe it will be evident by the new angle that would impose at the hitch point???), etc.

[HowieE]

How do you disconnect hydraulic, self leveling shocks while towing?

I have not seen this system but I have to assume it has an electrical component. If that is the case I would assume there is a fuse that can be removed while towing.

Hydraulics alone could not be self adjusting.

[funkill]

the catch to my question was *while towing*. My attempt at adding some humor. Future attempts will be refrained. I was imagining me trying to do something other than just reading the paper *while towing*. Sorry. Refrain didn't last long.
Laura

[Tom Nugler]

Originally Posted by HowieE

Hydraulics alone could not be self adjusting.

Add some valving, differential hydraulic chambers and a pump. I've seem these on Volvos, didn't know it was the same system as used on the GMs.
Brake & Front End: The Complete Undercar Service Magazine - Nivomat Shock...

om.

[funkill]

Originally Posted by HowieE

How do you disconnect hydraulic, self leveling shocks while towing?

I have not seen this system but I have to assume it has an electrical component. If that is the case I would assume there is a fuse that can be removed while towing.

Hydraulics alone could not be self adjusting.

After my recent trip to the shop, I found that the shocks are fully mechanical. No electrical component what-so-ever. The mechanic even demonstrated by jumping on the bumper for quite awhile times to show how the shock became more *rigid* and pumped itself up a bit to overcome the bouncing. At least that's how he explained it. Though I couldn't discern a change in final bumper height after the bouncing!
Laura

[funkill]

Originally Posted by HowieE

I have not seen this system but I have to assume it has an electrical component. If that is the case I would assume there is a fuse that can be removed while towing.

Hydraulics alone could not be self adjusting.

After my recent trip to the shop, I found that the shocks (self-adjusting level-control) are fully mechanical. No electrical component what-so-ever. The mechanic even demonstrated by jumping on the bumper for quite awhile to show how the shock became more *rigid* and pumped itself up a bit to overcome the bouncing. At least that's how he explained it. Though I couldn't discern an increase in final bumper/hitch height after the bouncing!
Laura