Driveway Incline Issue

Grit dog wrote:

valhalla360 wrote:


With the pictures, it's an easy solution.

When you get to the point shown in the pictures, put a couple 2x10 boards behind the trucks rear axle (double them up if you need more height).

As you back up, the rear axle of the truck will ride up on the boards lifting the hitch with the rear axle.

Once you get the rear axle onto the driveway up-slope, you should no longer need the boards as the rear axle will be going up based on the driveway slope.

Keeping the WDH bars connected will help also as they reduce the hitch weight and thus the trucks rear springs from compressing as much...net result is the hitch will sit an inch or so higher.

If you read the first post, he is using boards and the wdh scraping is worse than no dist bars and a saggy butt.

Yeah, read the first post. Disconnecting the bars likely will make it worse as it increases the hitch weight dragging the butt down further and the truck hitch will be more likely to hit.

Based on the picture, I see no way using boards is going to make it worse.

Grit dog wrote:
@Jbarca. If you’re talking about the few years of weak hitch GMT800s, I understand that, however the answer is the same. There is virtually nothing he could do backing into a driveway at 1mph that would cause greater stress than what is experienced while driving.

And if the hitch is that bad, I’d rather have it bend or snap in my driveway than at 70mph down the freeway.

And if this is not what you’re speaking of, then I totally don’t understand what you’re cautioning against.

Grit dog wrote:
Alot of explanation largely unrelated to getting a trailer in your driveway that has already survived a trip to (wherever) and home again.

But I gotta ask, what the heck is the dial indicator on the hitch for?

Grit,

I can understand your point of view why you may not understand where I am coming from. Asking me to explain, is a more preferred request then the wording you have been using….

You have given your opinion, and I respect it, even if I do not agree with it. However, you have not explained your position, yet anyway. It seems you are stating your opinion without explanation. If I missed it, I apologize.

I’ll try and make as this short as I can, there is a lot to this. After dealing with this flexing stress topic, on multiple trucks; my own, my family and my friends, I was speaking up to allenECUUNC for him not to go over the ratings of the hitch system as declared by GM in weight carrying mode given with what little we know about his truck condition.

If you want to read up on where all this started for me, there is 35-page post from 2005 here on RV net where a lot of the measurements and findings of stress issues associated with the GM receiver, and later, where with the frame stress/deflection after the GM receiver was changed to an aftermarket one.

Sadly, after that post was made, the forum software was changed and if any post used a “bracket” in the text, mine did, it would scramble the entire reply, pictures, and all. The photo bucket picture mess of a few years ago also scrambled a lot of the other posters problems. This link will drop you in the middle when I made the frame corrections. Word and pics are semi scrambled. http://www.coastresorts.com/cforum/index.cfm/fuseaction/thread/tid/16065296/gotomsg/16329138.cfm#16329138

I still have all the photos and a good memory of how my 2003 2500 Suburban had both receiver and frame flex. And how I addressed both once I understood the whole issue. Since that time, I have continued to run into the same GM receiver issues with other friends, the learning never stops.

Here are the cliff notes on some of the issues.

The first issue dealt with the original GMT-800 OEM receiver in WD mode. Some, not all, of those receivers had issues in use, well under the rating of the hitch. (The pin box as I call it, is the 2” square tube the hitch shank goes in and the 5/8 pin goes through). While I had good friends with no issues on similar camper weights, my experience and others was not the same. The amount of pin box wind up (excess rotation) trying to get WD to work, was poor. The pin box attachment flexed, rather than shifted weight to the front of the truck.

Some trucks I was involved with, the receiver bent up and permanently stayed up. Others, just weakened to the point WD settings would not hold and over time as the pin box/torque tube would bend and reset it’s unloaded position. Thus the WD settings where lost. After a few resets, the receivers were replaced.

Corrosion, the design of the receiver housed under the bumper left itself open for road salt slop to land right on top of the welded section where the pin box attached to the torque tube. And if allenECUUNC 2003 truck (19 years old) was exposed to salt corrosion, on the original GM receiver or an aftermarket one, the top of the receiver needs to be checked. The area that corrodes is under flexure stress constantly towing down the road. The heat affected zone of all the welds could be buried under corrosion.

Having dealt with enough corrosion-initiated failures at work, corrosion pits make a perfect crack initiation location. Once the crack starts, all it takes is time and flexure cycles under normal loading and the crack will run until there is nothing left to crack. With higher than normal loading or longer flexing, that accelerates the time to start the crack to run.

Pin box rotation, when the receiver is in weight carrying mode, the pin box will flex/rotate further then in WD mode. The receiver when it is brand new, is supposed to be able to handle the dead weight in weight carrying mode which will create a certain degree of pin box flexure that it can withstand. Going above the rating, with a tongue weight heavier then the rating, the pin box will rotate more than normal towing, more rotation is more stress. Not sure how you are disagreeing with this, please explain.

If the receiver is corroded, that added rotation/added stress can be the start of a corrosion-initiated crack. Or even a crack on non-corroded metal. A weld notch or defect can create the same crack initiation point if stressed enough.

Frame flexure, in my case, my Suburban receiver flexed enough while trying to get WD mode to work, the WD settings did not react. The pin box kept rotating; just very little weight was moving. I changed the GM receiver to an aftermarket receiver. The Putnam receiver I picked had a higher rating and there was less pin box rotation because of it.

During more testing, I now find the frame is flexing as the receiver is no longer the weaker link. This is where the dial indicator comes in. It is measuring the frame deflection under static conditions. This GMT-800 frame was made from thinner, yet a higher yield rating alloy then the prior vintage. I’m assuming they were going after weight savings while retaining overall frame strength. The rear of the frame has a very thin lower flange where the receiver bolts to. They had to employ the bumper hitch to help shift the forces from WD into the main frame. There are side brackets where the bumper hitch bolts to the main frame that helped get the WD forces into the main frame. After I found the frame flexing, and affecting WD, I created a method to utilize the top flange of the frame to help hold some of the load. I did this modification and accepted the responsibly of doing it. The frame flexing was greatly reduced.

Six years ago, my son gets a 2001, 2500 Avalanche (8.1L with the 3.73 rear end) to tow his 8,600# camper. Same frame as my Suburban. This truck lived in the rust belt of Ohio, even though it had a low 46K miles on a truck this old, frame rust was evident. For sure, he changed out the GM receiver which had heavy corrosion in the top of the receiver. Two years later he sees the bumper rising a full inch up and touches the tailgate when he hooks up the camper. His frame was flexing from a 1,000# TW camper using WD. We did the same frame reinforcement as I had and changed to a different receiver with a third extra-long reach contact mount to the frame. Now, for the last 4 years, WD works like it should and he has a great TV.

So yes, I cannot see any good coming from telling someone intentionally to use any receiver in weight carrying mode attached to that style frame over what GM rated the weight carrying limit. We have no idea if the frame is where the receiver dead weight rating came from, or the GM receiver, I suspect it was both. Now add in a 19 year truck allenECUUNC has, which is still a good truck, but how can you or I, or even him, know if a prior owner did not abuse the frame of the truck not even knowing it?

And then there is the corrosion issue if his has it. I agree, one or a few more times going up and down is driveway may not cause a total failure, but keep repeating it after the start and end of every campout, how many abuse times in the weight carrying mode will start a crack that later shows up under normal towing?

And the backing up hill part. You state 1 mph, have you ever tried in that size GM in 2 wheel drive to go 1 mph, starting out pushing a trailer uphill? Granted you not going fast, but not a nice slow even start of movement either all the time. You have to rev the engine up enough to get the torque converter to engage, there can be a jolt getting the trailer to move up hill. That jolt goes right into the hitch connection where the hitch shank is pointing down hill in weight carrying mode no less. The pin box is going to flex down and potentially more rotation then the ratings and safety factors of the receiver allow. And not every time is perfect, an accidental goosed it too much on the gas pedal, and the receiver in weight carrying mode just got stressed more again trying to get going. This is not a good situation to be in. Avoid it. Find a better way with the WD bars on.

I’m providing reasons on why not to over run the rating of the system in weight carrying mode; can you help explain how it is OK to do so?

I hope this explains it some where I'm coming from on this.

valhalla360 wrote:


With the pictures, it's an easy solution.

When you get to the point shown in the pictures, put a couple 2x10 boards behind the trucks rear axle (double them up if you need more height).

As you back up, the rear axle of the truck will ride up on the boards lifting the hitch with the rear axle.

Once you get the rear axle onto the driveway up-slope, you should no longer need the boards as the rear axle will be going up based on the driveway slope.

Keeping the WDH bars connected will help also as they reduce the hitch weight and thus the trucks rear springs from compressing as much...net result is the hitch will sit an inch or so higher.

If you read the first post, he is using boards and the wdh scraping is worse than no dist bars and a saggy butt.

allenECUUNC wrote:
I cringe every time I see this. This is with the roller ball on and my wife says everything looks great. I think we need to take the roller ball off and use boards. This is the part of driveway that gives issue and it scrapes the hitch so that is why we added the roller ball.

https://ibb.co/fYTSZp4
https://ibb.co/mBzWhVp

With the pictures, it's an easy solution.

When you get to the point shown in the pictures, put a couple 2x10 boards behind the trucks rear axle (double them up if you need more height).

As you back up, the rear axle of the truck will ride up on the boards lifting the hitch with the rear axle.

Once you get the rear axle onto the driveway up-slope, you should no longer need the boards as the rear axle will be going up based on the driveway slope.

Keeping the WDH bars connected will help also as they reduce the hitch weight and thus the trucks rear springs from compressing as much...net result is the hitch will sit an inch or so higher.

opnspaces wrote:
Thanks John, I had to read it a few times but I think I get the gist of the weights.

I'm still on my factory hitch and until I see if looking like something is wrong I'll probably leave it.

Anyway I don't want to detract from the original post so I'll open a new topic if I want to explore it further.

So why don't you just raise the trailer tongue up with a taller hitch to get it into the driveway, or am I missing something?

Thanks John, I had to read it a few times but I think I get the gist of the weights.

I'm still on my factory hitch and until I see if looking like something is wrong I'll probably leave it.

Anyway I don't want to detract from the original post so I'll open a new topic if I want to explore it further.

Alot of explanation largely unrelated to getting a trailer in your driveway that has already survived a trip to (wherever) and home again.
But I gotta ask, what the heck is the dial indicator on the hitch for?

opnspaces wrote:


But we all know that for every action there is an equal and opposite reaction. So doesn't the hitch weight go up and I assume substantially if he leaves the bars hooked up through a angle such as in the pictures and gives an angle like \/?

The dry weight of his trailer is 4,790 lbs with a hitch weight of 560. These weights are very similar to my trailer which when fully loaded has weights of ~ 6,000 and a tongue weight of ~ 850. So is it better to leave the WD hooked up and put a ton of weight on the hitch with the angle like a \/ or is it better to go with the bars off?

Hi opnspaces,

Good questions, I'll add some thoughts about them. Think on this a few moments.

To your first paragraph on does the hitch weight change if the truck and camper are in a V configuration? From what I know, the answer is no, the hitch weight does not change. Meaning the actual loaded hitch weight of the camper unhitched from the truck does not change.

What does change is the loading tension on the WD bars. Think of this situation which you may have encountered over the years. It is sort of a classic case of back flexing so to speak of the WD hitch. Here is the example.

You are towing down a back country road to camp. You approach a large high up RR crossing. The RR tracks may be a good 4 to 6 ft. above the road bed approaching the tracks, the road levels off a little over the tracks and then the same 4 to 6 ft down hill drop when leaving the tracks.

The truck and the camper will go into a V back flex configuration on the WD hitch when the truck starts going up the hill. The truck is up hill, the camper wheels are still on the level, they are now in a back flex condition. A similar situation exists on the way off the tracks and down the other side. The truck ends up on the level road and the trailer wheels are still up on the hill.

In both cases, when the back flex occurs, the WD bars start taking on extra tension from the hitch head rotating back towards the camper when the truck moves. The WD bar tension increase is sort of like tilting the hitch head back when you want more weight transferred to the front of the truck. Just in the back flex condition, the truck and hitch head is what is changing by the road it is driving on in relation to the TT. The trailer hitch weight does not change, the WD bar tension does change and it can be substantial pending the amount the hitch head rotated back towards the camper.

And visa versa, the WD bars will unload tension when the truck reaches the top of the hill going level over the tracks and the camper is then still going up hill. No back flex is occurring here, it is the opposite condition. The WD bar tension goes down, way down below normal tension. In this case, the hitch head rotated away from the camper in relation to the TT as the truck drives over the level tracks and the camper still on the hill unloading the WD bars. The camper hitch weight never changes, the WD bar tension does. Agree?

OK now to the second paragraph question in blue. First I'm going to talk about when the truck and camper hitched up, the WD is engaged, and both are standing still. Think about this for a moment. The WD hitch settings create a certain WD bar tension when the camper & truck are standing still. TV & TT might be on a flat surface, or at an angle to each other. At this point, the WD system is in what I call, equilibrium. Meaning, the WD bar tension is not getting any stronger or weaker. The back of the truck not moving up or down and the camper ball coupler is not moving up or down. The WD system is in equilibrium. Agree?

There is something else going on during the large WD bar tension rise during a back flex of the WD hitch. Again the hitch weight is not changing any time during this, but the WD bar tension does. I'm going to now call out a new made up term called, truck lift. I'm sure you can envision when the WD bars gain enough tension, the back of the truck will lift up. How much truck lift depends on the amount of tension increase in the WD bars. The truck will also drop down when the WD bar tension goes lower. Agree?

So yes, during the "start" of the back flex situation, the WD bar tension rises. If you go over the RR tracks real fast, the tension can spike up real fast. If you go slower, the WD bar tension rises slower. In either case, the fast over the RR tracks or the slow over the RR tracks, when the WD bar tension rises up enough, truck lift starts to occur from the added WD bar tension. When the back of the truck goes up high enough from truck lift, the hitch head angle changes again. When truck lift gets high enough, WD tension starts going down and equilibrium is approaching. Pending how long the hill is before the trailer wheels start reaching the hill, there may be a few truck lift events occurring. Once truck and camper wheels are on the same plane, the WD system is back to equilibrium. In all this, the hitch weight never changed, but the WD bar tension did. Agree?

Now do you take the bars of or leave them on during a large back flex situation? Part of this answer "depends" on your truck receiver, truck frame and the WD hitch head. If your truck receiver, the truck frame and the WD hitch head & shank are all rated to handle all the dead weight of the loaded TT tongue weight, then the WD bars can be off in my view as long as you are not dragging the ground. NOTE: I'll add one qualifier to this, as I see you have a 2001 2500 Suburban, that is one very nice truck. Hang onto it as long as you can. I had a 2003 K2500 Burb and it even had the quardasteer on it. I miss that truck. But, I would not on purpose every campout put the original GM receiver into a large back flex up hill condition that approaches the dead weight ratings on the original GM receiver of the GMT800 trucks. Two fold, the receiver itself flexing and due to the frame flex where it mounts. The original GM receiver issue is a different issue/topic. By chance, did you change your receiver off the OEM one?

If any of those components are not rated to handle the dead weight, (truck receiver, the truck frame and the WD hitch head & shank) then use the WD bars and go slow over the large back flex area. The WD tension rise is slower, the truck lift effect will start lowering the WD bar tension back down as the backing up of the truck is occurring. It might truck lift a few times, but it is all slow as that one the one variable you can control, the speed of the truck. Your 850# dead tongue weight is over the GM receiver rated limit so you are into using the WD bars in my opinion. If you changed the receiver, we need to talk about the frame flexing issue if you have an aftermarket receiver on the truck.

When backing up hill from a level spot and turning at the same time, the hitch head angle changes even more dynamically. Pending the angle of the turn and the amount of up hill rate change, one of the WD bars is increasing in tension while the other is loosing tension. One WD bar is holding the whole hitch when the angles gets large enough. This happens all the time while towing, just the up hill backing up with the back flex is added to all this. Again, going slow is under your control.

Does that help answer your questions?

Hope it helps

John

@Jbarca. If you’re talking about the few years of weak hitch GMT800s, I understand that, however the answer is the same. There is virtually nothing he could do backing into a driveway at 1mph that would cause greater stress than what is experienced while driving.
And if the hitch is that bad, I’d rather have it bend or snap in my driveway than at 70mph down the freeway.
And if this is not what you’re speaking of, then I totally don’t understand what you’re cautioning against.

Hi Grit,
I stated this to the OP, allenECUUNC

JBarca wrote:
Snip...
I have a few comments/thoughts.
First, from my background on GM truck receivers, I recommend you to “not” take the bars off your hitch with that style of GM truck receiver you have. You are overloading the receiver by the name tag, and worse, you are backing up hill putting excess downward force into the truck receiver. Both are not doing any good for that style of receiver.

You stated

Grit dog wrote:

@Jbarca, what you said couldn’t be further from the truth regarding damage to the hitch or receiver back into the driveway. The only part of that equation getting stressed is the (presumably) old factory air shocks. They’re pretty reliable but…OLD.

Not sure why you picked the wording you did, and I don’t want to jump to assumptions about the wording. How do you know my background, the GM truck frame, and GM hitch failures I have seen, researched, and dealt with? Being open-minded, I will give you the professional curiosity to explain your point of view. Please provide details to support your position that there is no stress on the truck receiver or frame.

First, I agree with you. If the truck in question came with and still has the original GM autoride (air shocks) on a 1500 SUV, (auto adjust shock damping on the 2500 with the Suburban/Yukon XL) and the air shocks are still original, they could be into a stressing situation. I am not disputing this; I agree with it.

If the OP’ers “older” truck still has original air shocks that still work on a 19-year-old truck), it’s a rare thing. Many can’t afford to replace the OEM parts and convert to a helper spring shock (coil spring over a more standard gas shock) and deal with changing the system program not to have air shocks. No dispute here. But we do not yet know if he even has the autoride feature. My 2002 Tahoe did not come with autoride, it was an option. Leaf springs in the rear with good gas shocks was it.

I do not recommend suggestions to fellow campers without prior knowledge of the topic. I do not shoot from the hip. And, I have learned long ago from doing enough machine failure analysis, not to assume one knows everything about the failure. I keep an open mind and listen to any input, then make up my mind from all the data. And admit if I made a mistake. In this situation, I still stand behind my recommendation.

After looking closely at allenECUUNC’s truck and camper picture, I can see someone has changed the original GM receiver with an aftermarket one. From this pic I zoomed in on, this is not the GM receiver.


We both need to know more about his truck history, the rating sticker off the aftermarket receiver, and the brand and size of the WD hitch he is using. Then we can talk more specifically about the issues of backing uphill without WD bars on.


allenECUUNC, , can you please provide us with this info so I can explain where I’m coming from on your specific situation?
We need some info on the truck history, as you know it.

1.Did you buy the truck new or used? If used, what year did you acquire it? I'm after the prior towing history if obtainable and if they used WD or not when towing. And if you used it, what weights did you tow?

2.Do you know when the truck receiver was changed? It might have come with it if you bought it used; just asking to get some background on what the owner found to change it.

3.Can you get a pic of the rating sticker and brand on the receiver? There should be two ratings, max tongue weight in weight carrying mode and one for weight distributing mode?

4.Do you know if the truck was ever driven in a northern state where road salt is used? A good sign if the truck was driven in the rust belt in the winter is, the condition of the truck frame. Have a look at it. Trucks from non-northern snow states look very different under the truck than ones never driven during winter months with salted roads. The GM’s of that era are known for brake lines, transmission lines, and fuel lines rotting out from road salt, not to mention frame corrosion.

5.If you can post a picture of how the aftermarket receiver bolts to the frame of the truck would be helpful. Looking for a shot like the two below. Ideally an inside and outside the main frame pic. This is off my 2003 2500 Suburban with a changed out GM receiver to a Putnam receiver. Don’t mind the dial indicator in the pic; I was measuring frame deflection back then.

Outside the frame


Inside the frame


6.The brand, model, and ratings on your WD hitch.

7. Tell us if you have rear air shocks and they are still working, or what you have for shocks.

These answers can help me talk specifics about the concerns and failures I have seen and if they exist on your setup.

Hope this helps

John