I have been reading up on every GM hitch post on this forum going back 1 year. I am also the proud owner of 3/4 ton new body style 2003 Suburban for my TV. A great Truck.
However the folks who have had hitch failures is concerning. So I took to upgrading and measuring the deflection before and after the installation. I am amazed at what I found. This post is a little long & windy but it has the detail in it and not just gut feel. Well almost none. Hopefully the GM owners who have had failures can chime in here to help with the discussion.
To try to confirm or deny what other forum members have been saying I measured, documented and took pictures that I want to share here for conversation so we can all learn.
I still have a few unanswered questions, but I have learned a whole lot in the process.
Here is some of what I learned.
My spring bars are to light for my tongue weight. Unless you actually measure the tongue weight you have no clue and neither did my TT dealer who said 800 # bars where OK. I used a Tongue Jack with a pressure gage to measure this. I have a 1,100# tongue weight and it increases to 1,400# when I fill up my fresh tank. So far I have not towed with a full fresh tank and good since my hitch is only 1,200# rated.
The amount of deflection of the GM hitch was amazing. This was measured down the centerline of the truck as the hitch would deflect when I hooked up my TT. I did not measure side to side turning deflection. The also amazing part is the Putnam also deflected in this manner as well. The failures I have seen seem to be more side load related than up and down. This may be the week link of the GM.
I basically put a 4 foot level across the top of the bumper as a datum line. I then measured from the top of the level to the bottom of the tail gate, using the tailgate edge as what I thought was a datum that I could use as a reference point.
Here is the shocking part. I started using a dial indicator thinking I was measuring a small number. Well after the 1st time I put the tongue on, I went to get my scale.
After doing the GM hitch I switched to the Putnam Hitch and repeated the same set up. However this time I also had my fresh tank filled so I could increase the load to 1,400# and then go down to 1,100#
I also learned when I went to the Putnam that the receiver tube is about 2 1/2" higher and I needed a new hitch shank. In the end this was a good thing as the pin length was longer and give me more turning radius plus the holes for vertical adjustment are finer in adjustment to level the truck out.
OK now I saw similar deflection in the Putnam. This was an eye opener. My method of using the tail gate has issues. There is nothing bottled to the bumper but yet the bummer to tailgate still changes. I do not know exactly why but the body is on rubber mounts and it may be lifting somehow.
So I added a new dim, D on the chart which measures the deflection of the top of the Putman to the bottom of the bumper which now has no load on it since it is not bolted to the bumper. Here the deflection from a no load state to both spring bars engaged under laod of 1,100# was only 0.047" I could not reproduce this on the GM hitch since the hitch was already off and bolted to the bumper itself.
SO I fell better about only the 0.047" deflection of the Putnam measured in this manor.
This past weekend I was also at a camp where a lot of GM trucks where including my brothers new 2005 3/4 ton Silverado. I went and look at his hitch. GM added a plate in the middle of the hitch that is not on my 03 3/4 ton Burb. I also looked at a lot of 1/2 ton newer trucks 03's and 04's and they had the same no plate design like I had. So GM added something for some reason.
So after seeing all this and seeing the failures on this forum, they appear to be side loaded or twisting the hitch off going around a turn as opposed to an up and down break.
It would be nice to know what their tongue weight was and what WD hitch they had and how it broke the GM hitch. My new Putman is very reinforced in the left to right direction even though it does deflect up and down some like the GM hitch.
Any input of why the truck body is rising when I add a load on the hitch and thought on the twisting failure mode?
Any and all comments welcome.
Hope this helps someone in the future. And oh yeh, check your tongue weight, it's allways heavier than you think...
Happy camping
John & Cindy
2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10
CC, SB, Lariat & FX4 package
21,000 GCWR, 11,000 GVWR
Ford Tow Command
1,700# Reese HP hitch & HP Dual Cam
2 1/2" Towbeast Receiver
2004 Sunline Solaris T310SR
(I wish we where camping!)
I just went to check on my 2005 Silverado with factory tow package and it appears that it is the newer GM style if I follow your post correctly. See hitch
Steve
Steve, Marty, Duke and Duchess
2005 Hornet 25FL
2005 Chev Silverado 1500 4X4 Ext Cab 5.3L 310 HP
Reese Receiver and Sway Bar, WD System
Clear Skies and Happy Camping!
I would say that the difference is because the end of the frame rails are being twisted downward causing a bow like effect on the chassis forward of the hitch . That will give the illusion of the body rising when it is really the ends of the chassis bowing towards the ground.
Rich
Rich, Fern, Bethany, Justin. 2005 Ford F450,Lariat, 6.0 PSD,CC,DWR,4WD, Air Hitch, 100 Gallon Aux fuel tank.
2009 Cardinal 3802BH 5 slide, 2 bath
Our "Condo in the Woods"
Leave no roller coaster unridden!
John, good analysis. Hard to be 100% precise with field measurements like this, but I think you are close enough to illustrate the point. Many RVers on this forum have reported excessive vertical flexing with their OEM receiver, but in my case I believe the weak point was its inability to resist lateral forces. Especially in my case, I think the Hensley hitch may have exerted higher-than-normal lateral forces on the receiver. I have advised Hensley that as a service to their customers, they should warn against using the HA with GM OEM receivers.
The Putnam in your photo looks virtually identical to the Draw-Tite I put on my Suburban. Much stouter than OEM. I think the plate that GM added inside the vertical mount is designed to do just that....resist lateral flexing. My feeling on this is that the original receiver is designed to carry the rated load in a static environment, and that the designers did not adequately account for additional forces applied from bumpy roads, stopping, turning, etc.
I think about this in the same category as the Firestone SteelTex tires that came OEM on the truck. "Many" people have traveled "many" miles without incident, but mine developed a few odd bumps and bulgers, so I swapped them out at 15K miles with more than 50% tread left. Better safe that sorry....unfortunately there are too many folks that think somebody else should pay for their pound of cure because they refused to buy the ounce of prevention.
John, Nice job of explaining the flex that almost all factory or aftermarket receivers have to some degree or other. The problem is in the design. The hitch shank is inserted in the centre of the receiver's span, it's weakest point. This is how I solved the problem which a common.
The other issue that is directly related to the receivers flex is the distance the ball is to the back bumper. The farther away the ball is the more leverage it has to cause flex. I use a welded ball mount which places the ball just 3 inches from the back bumper. If using an adjustable mount the distance can be 5 to 12". If 12" or more you have just added a substantial amount of force on the receiver, thus inducing unwanted flex and the potential for problems.
Airstreams.... the best towing trailers on the planet!
Hi John,
Excellent work. I've just looked at your pictures and it shows the methodlogy employed. I agree with you.
I too have a back ground in the industrial markets. Factory automation (largest indoor system in the world), industrial controls, motor controls, robotics (largest in the world), process control, etc and have designed may systems (computer, electrical, hardware) for these industries and more: food, wood, steel, plastic, automotive, aviation, transportation, defense, military, shipping, municipal, etc, etc. As a partner in most of the small firms, we couldn't afford the expensive forensic experts (replacing others failed equipement, our failed equipement, etc), so learned from working/watching/coping other firms expertes (both internal and consultants).
Have enough back ground (aka...an old guy) to be able to look at the system to know enough about the design to see/say POS.
Now to the architectural basics between the two designs and how your testing confirms.
The POS GM OEM new body style receiver is not of traditional design. It isn't designed to use the round cross bar as the main transfer agent to the TV frame. It depends on the "box" between the round cross bar, bumper, bumper brackets to frame rail and the frame rail of the TV.
If that "box" was stout enough, sure it can do it. But it's not stout enough and your measurements prove it. "Stout" meaning stiff/strong/etc enough and not move enough to negate the forces applied to it. That applied force is then supposed to be transfered to the TV frame rails, which is the whole point of this system.
The "box" section is why the POS OEM GM receiver is lower. The gusseting to form that "box" lowers it vs the traditional design, which does **NOT** have a box section, nor does it need one.
Plus with that "box" section, they did not design in enough laterial strength, nor any other direction other than up/down loading.
"Stout" enough meaning that the components must be strong enough to NOT bend, nor move, etc.
I won't go into the engineering of fastener science, but lets just say the clamping forces of the bolt size/grade/location/etc isn't up to the task.
Then the bending moments and lever arms are all wrong for the fastener sizing and location of the whole system. The bumper was never intended for this job and the meek redesign very sad showing of engineering and budgeting for that program.
Now to the traditional design receiver. It does not depend on anything else, other than itself to transfer the forces to the TV frame.
The cross bar is a torsion bar. The receiver pin box is welded to the cross bar along with a bunch of gussets. The cross bar then twists (torsion), or resists the twisting forces.
This then transfers the forces to the end gussets or the brackets that is bolted to the TV frame rails. This is like shoving in a 5'-6' long x 2" square steel bar into the receiver pin box. Then lifting with the sum of the forces both WD bars impart onto the receiver pin box. Think of a 5'-6' long crow bar, as that is exactly what it is doing.
John measured the POS OEM GM receiver movement (bending).
Anyone who can't transfer weight to their TV fronts is experiencing receiver bending and consuming the forces before it can transfer them to the TV frame (or their WD bars aren't large enough).
A VERY GOOD write-up by John.
[red][b][edit]....[/red][/b]that "new" gusset inside of the other gussets is just a bandaid and only improves the old POS design a tiny "bit". Not nearly enough to come even close to the traditional design receivers that cost around $150 bucks for the best plus about 1 hours labor to remove/install.
PS...there is even more movement than what you measured, as the receiver cross bar also bent downwards during the loading process. So the total or "effective" movement is around twice what you measured, if the pivot point is centered on the receiver pin box.
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-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...
Thanks so far for your response. I didn't know if folks would read my post as it is long, but I figured if I added the back up and pic's, it would keep the interest. Looking in the Towing Forum section just now there has been 260 hits on this post in less than 24 hours, so some folks are at least starting to read this and maybe help educate themselves as well, like I did.
This forum has helped me greatly so I figured I would take the time to give back to help others. We just have that camping sprit here on the forum.
This hitch deal has had me concerned for some time as my 6000# TT and higher tongue load is high enough to worry about this. For those who have had complete failures my heart goes out to them as that is one scary deal having your hitch break loose.
Between the money tied up in my TV and TT and God forbid some get's hurt, the $149.68 (including freight)I spent at Southwest Wheel is not that much. Even where to go get the hitch was a tip from a fellow forum member that he did this on his 3/4 ton Burb.
Hopefully some more folks who have had failures can post here on
What you tongue load was
What your TT weight is
What brand your of our hitch
And something about how the failure happened.
So even if we are not chiming in the discussion, they may pick up, gee maybe I should go check this out too. That's what I did.
I checked with GM on my 2005 Silverado hitch package and was told that they are not factory installed but rather installed at the dealer. Now that has me wondering if all dealers are using the same packages. After reading your first post I also looked at the Hensley Hitch. Man it has to be a real winner for the $3K price tag. Now I have to wonder what the listing of best recommended hitches are. Anyone know of a list of higher rated hitches?
I checked with GM on my 2005 Silverado hitch package and was told that they are not factory installed but rather installed at the dealer. Now that has me wondering if all dealers are using the same packages. After reading your first post I also looked at the Hensley Hitch. Man it has to be a real winner for the $3K price tag. Now I have to wonder what the listing of best recommended hitches are. Anyone know of a list of higher rated hitches?
Steve
Do not know who told you that GM does not make the hitches. The RPO codes in the glove box call out the factory tow package and the window sticker has it listed from the factory. Infact if you follow this post, there is even a GM part number for it. Prior post talking about GM hitch part number Scroll to the top of the post.
Now the pic of your receiver must be on a 1/2 ton 05 Silverado. My brother has a 3/4 ton 05 and the pic I showed in my post was of his 3/4 ton. Brothers 3/4 ton 2005 Silverado It had the plate welded inside, yours did not. My 3/4 ton 2003 Burb had the hitch that looks just like yours. They may have only added the plate to the new 05, 3/4 tons.
To your question on good hitches. There are receivers and then WD hitches. These are the ones I know of that are good.
The Hensley I have investigated and heard is is top flight. However in my case my TT is balanced such that I do not have much sway even running without any sway controls. So the Dual cam I have covers the times when things are not perfect and I need some sway control.
There are others just I have not investigated them.
Ok. Did some research and found that the Putnam is a fairly well used hitch. Now, according to my TT info, my tonge weight is 640 pounds but I really doubt that includes the 2 - 30 pound LP tanks. It appears that I can get a class IV or class V (XDR) hitch for my 2005 Silverado 5.3L Ext. cab with about $10 difference. I have to figure that seeing how this bolts to the frame of the truck that it should not interfer with my 17" spare tire. Any thoughts on getting a class V even though with my 2005 Hornet 25FL it would be overkill? Just never know what the next TT might be. It looks like my dry weight and load capacity would max out at about 6,200 pounds. The truck is rated at 7,700 max trailer weight and 13,000 GCWR.
Guess I should also mention that I have the weight dist bars, receiver and 1 sway bar.
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