Too Much Weight For Reliability?

[cocco78]

HI coco,
I'm only going to comment on a couple of your points. First, I am an engineer. I didn't think it was so obvious. It must be my bad spelling!! Engineers are famous for their bad spelling.

LOL, no it wasn't your spelling. Engineers just don't seem to take to criticism very well, especially from non-engineering types. They have a hard time realizing even less educated people can be correct or have good idea's, or that first hand experience can out weigh numbers on the computer... BTW, i'm an aspiring engineer myself :sombrero:

Your statement about the vehicle not getting tippy in a crawer build if it is used in an expedition application is wrong. It most definitely does get tippy if you have a loaded top rack, high lift, and big tires. This is very unstable in off camber situations unless you keep the rig low. That is one reason why rock crawlers and expedition builds have such different needs. Crawlers don't make good expedition vehicles and expedition vehicles do not make good crawlers. Very different animals. Very different needs. It's all about trade-offs.

Actually your not exactly correct. Crawlers need a low center of gravity to work well, and a stable and flexible suspension as well. Crawlers have all their weight down low, especially with much larger and *wider* axles. I have only lifted my Jeep with 3.5" lift springs and swapped to 1 ton axles and 37" tires, and i'm considerably wider than stock at 81" from outside of tire to outside of tire. I would bet your average rock crawler would have near identical COG or maybe lower than your average fully equip expo rig. And it wouldn't be an uneducated bet as I've had to calculate COG, roll axis, squat and anti-squat in properly setting up my suspension to get it to function predictably. I also would never stack all that stuff on the top of a rig, its just poor execution to a problem. But it does give your vehicle the "expedition" look so many here are after. But it is a trade off, like you said, for having a small vehicle tho, stuff needs to go somewhere.

You will be glad to hear that I decided to install a truss. I did some research and called a few manufacturers and this is what I learned.

I have the best of the D35 versions. I have a non-C clip differential. I knew that but I did not realize why it was the preferred D35. That's good. The axle bearing each have a load rating of 2200 lbs. for a total load capability of 4400 lbs. My max total rear axle load is 2820 lbs. That gives me a total head room of 1580 lbs. That's significant and sufficient for reliable performance. Spyder issues are taken care of with my ARB. The ring and pinion are plenty strong for my application. My upgraded axles removes the axles as a concern. The one remaining issue is the case and tubes.

Superior suggested (are you listening, coco) that I get an axle truss which will solve the case and tube flex problem. The engineer at Superior calculated that my existing D35 with a good truss will be fine for my use.

I'm sure your well away as you reach the max rating for things such as bearings reliability start to go down. 2200lbs is not a finite number that all is good below and destruction is sure to happen above. Under severe duty parts will fail at a higher rate...

But really, I wheeled my Jeep pretty hard around the country with a bone stock D35, 33" mud tires, and an aussie locker. I don't think the 35 is a throw away axle, it just needs some love to make it better.

Since anybody can say anything, I need a reason to trust any given individuals view. In this case, I called Superior checking into their Super 35 axle. As you know, that's a pretty expensive option with its included ARB locker. So, Superior would have made much more money if they had said "Your D35 is trash and you must replace it with our super good Super 35". I would have listened. But that's not the direction the conversation went. Instead, he led me away from the reason I called and justified the truss as a good, reliable choice. I was impressed with his technical knowledge and his overall appreciation of my vehicle needs.

Sounds like a good company to deal with...

 

[leaffreux]

Good on you COCCO78, you make a lot of common sense.
I am also an Engineer, but remember their are two kinds.
One kind is numbers kind, crunch it out and believe it can't be wrong
Then there is the other kind that have to organize and make something happen. I am of this second kind making projects work in the offshore oilfield
in the Gulf of Mexico. Same goe's for making a Jeep work.:costumed-smiley-007

 

[Root Moose]

Ditto here. I was the numbers kind but something happened over the last ten years or so.

 

[Karma]

HI,
You guys are not inspiring confidence in me. I'm not going to argue engineering philosophy here. I will say the best engineers use both numerical analysis and experience to create their designs. I have worked in the space program and the nuclear field for all of my nearly 50 year career. I have worked with brilliant engineers and I have seen the ordinary ones. The brilliant ones were numerical marvels and had the experience to know when the numbers should be questioned.

I can assure you that a space craft or nuclear reactors were built using extensive numerical analysis and modeling. Without those tools, you are lost.

Your arguments are those of amateurs. BTW, I'm not an ME but an EE. But in my field the same factors hold true. I'm smart enough to consult with my ME friends and co-workers which I have done throughout my Jeep build.

I'm glad I did not take your opinions (that's all they are) without analysis as truth. You should not wonder why I questioned your views.

Sparky

 

[Karma]

HI All,
Perhaps you will be interested to know that I reweighed my Jeep today. This time I removed all the camping gear and top storage. No chain saw, no gas or water cans. This would be the case if I were taking a day trip on the local trails or pulling my trailer to Moab for a series of day trips.

Most of the creature comforts were still there like the refrigerator, cooler, computer, etc.

The weight came down to 4760 lbs. I consider this to be to lowest weight this Jeep will see.

Sparky

 

[cocco78]

:sombrero:

I like engineers! don't get me wrong. The best prof I ever had was a by the books retired aerospace engineer from Lockheed Martin... His classes were the hardest classes but the most fun as well. I was so the exact opposite of him, but we got along great :victory:

Back the D35...

I honestly think you'll be fine after the truss. The big thing with that axle and even the alum D44 in the later Jeeps, it will bend under alot of weigh. Like cambered trailer axles and how they straighten out with weight on them. To many people badmouth it.

 

[JPK]

Analysis gets you to a testable hypothesis. Nothing more.

But apparently the Superior and the OP's own analysis wins the day. This from the same OP who asked, rudely: "What exactly have you seen and experienced with respect to JEEPS and the expedition experience.[sic][?]

And who also wrote: " It just that my experience tells me otherwise. It's hard to go against that but I'll try."

So, there are many telling from their EXPERIENCE that 1.) the Jeep is grossly overloaded 2.) for the stock D35.

So, which is it, the OP's experience, contrary to history and other posters, and touted loudly, or numerical analysis? Each contrary to aggregate emperical evidence, btw.

As another (wise) poster wrote, "If you don't want the answer, don't ask the question." I'd rephrase to say, "If you already know the answer, according to your analysis, Superior's calculations and your own, why waste anyone's time asking the question?"

Go test your hypothesis, report back on whether it is just a bad SWAG or whether, contrary to history, the D35 holds up.

BTW, the truss won't help the wheel bearings, only the tube.

And load the friggin' trailer to take the weight (5200lb unloaded!!!) off the Jeep!!!

Christ, my JKU doesn't weigh that much.

JPK

 

[Karma]

HI JPK,
OK, how much does your JKU weigh and under what circumstances? Are you set up for a long trek? Have you actually weighed it? Most folks here have not reported actual weights. If you do not reply to this question then I'll assume you do not have a clue.

And if you had been paying attention, the wheel bearings are well under their maximum load spec. You sound like this factor has been ignored.

And if you had been paying attention, I do unload the Jeep when possible. But it's not possible on the trail on a long trip. The trailer is not there.

And BTW, it is 5200 lbs. LOADED. Are you having fun not knowing what you are talking about?

I get tired of repeating what has already been discussed.

Sparky

 

[JPK]

Karma,

So your "logic": The axle bearings and axle are rated for Xlbs service. You argue that they are sufficient because the weight of your Jeep does not exceed 2x the axle rating. But then you truss the axle, contrary to your own SWAG.

Moreover, the bearings own the same rating as the axle, why bother trussing the axle if the bearings are sufficiently strong? You simply end up with a stronger tube supporting weak bearings. No net progress or improvement.

Your "logical" thought process looks like a plate of spaggetti.

And yes, clearly you overlooked the wheel bearings.

Furthermore, you have things *** backwards. You are loading your Jeep for long trips off road. But the axles, bearings, springs, etc. ratings do not contemplate off road use. The specs on the axle do not take into consideration anything but pavement. {Think about it for a mere moment.... Here is an emperical example: Why does Jeep currently offer a D30 front axle and also a D44 if the D30 is sufficient. If the D44 is required, then why does Jeep offer the D30? Importantlly, why does Jeep equip the model specifically set up for off road with the heavier rated axle? The same in the past when Jeep offerred - iirc - the D44 on the Renegade and perhaps other upgraded models.}

Obviously, you have overlooked the rating regimen and failed to consider the entirely different use your Jeep, loaded, will see.

I haven't weighed my JKU on scales (though I think I will on Monday.) However, I have taken the manufacturer's advertised dry curb weight and added/deleted the weight of equipment added or deleted. Gear, fuel, etc, added or deleted to come up with what I anticipate is an pretty accurate estimate. But a run to the scales next week will confirm. Our company runs a fleet of trucks, and I have become pretty good at estimating the weight of our welding rigs, which often run within 5-10% of their max GVWR setting out for a job, just by looking at their loadout. All are subject to state and federal DOT regs and inspection, so weight is critical.

My estimate of my JKU's current weight is 5100lbs. That is half fuel, no gear, as she rides with the summer soft top and half doors. Compared to your Jeep, the JKU is HUGE. For that matter, compared to my '06 LJ the JKU is huge.

My JKU is on its way to being set up for long treks, but it is only three weeks old. It is a replacement for my LJ, which is further along, but has proven both too small and too highway unfriendly for a "month at a time" vehicle.

Even with the relatively large JKU, it is clear that, for my purposes, a trailer is all but required. I have a very nice M101A2 (US) that I think would fill the bill, but if it proves too large then an M416 (M101 Canadian) size trailer will do.

You need to look into the M416 style trailer to get the weight off your Jeep. The M101 and M416 trailers are off road military trailers with high ground clearance. The M101 is sized for a 3/4-5/4 ton truck or HumVee, the M416 for a CJ size Jeep, like yours. The original hitch for all of these is a pintle ring or lunette. Some have 360* rotating rings, some do not. Either hitch is capable of trekking, with the rotating lunette preferred. But it is my understanding that even a non rotating lunette allows a 60* variance between towed vehicle and trailer side hill angles. Tight fitting ring and hook are quiet, but not every combination is tight and there can be some bumping, banging noise. [Rotating pintle hooks are also available to overcome non rotating rings as well.]

OH! And by the way, here is the PERFECT EXAMPLE of weight rating for on road vs. off road. The M101 is rated to carry 3/4 tons off road, but it is rated to carry 1 1/2 tons over the road! In other words, the ultimate off road equipment authority, worldwide, the US Army, has determined that, at least for the M101 (but on and off road rating differentials are similar if not exact for other Army vehicles,) off road rating is 50% of over the road ratings. Wish I had thought of this example earlier, might have saved some typing.

[EDIT: Did some digging and it appears the over the road capacity of the M101A1 and A2 is 2250lbs of payload. So US Army de-rate for off road use is not 50% but 33.3%.]

Get out your calculator and go figure that out. I'll give you a hint: Your Jeep is OVERLOADED.

JPK

 

[cocco78]

My thought on the truss would be without it the axle can flex under load during severe use. The flex of the axle housing could put the axle shafts and/or bearings under an increased load causing premature failure. The addition of the truss could prevent this, and perhaps increase bearing life? Another thing i don't like about the D35 is the fact that the axle shaft itself is a "wear part".
the roller bearings ride directly on the shaft. this eventually can wear and gall the already small dia. shaft bearing surface. If I remember right tho, the OP had a non C clip, so the bearing would have inner and outer races and would be pressed on and this wouldn't pose a problem...

I still wouldn't put a dime in a D35.

 

[Patman]

The truss will solve any housing deformation issues, but.....

It will also increase the shock load on the axle shaft as the psuedo shock absorbing quality of the housing flex is taken out. So effectively the bearings and axles are now being subjected to more load, removing even more of the non existant perfomance envelope.

Sparky, I hope you don't let all the semi negative posts ( I have to admit that my first reaction is to agree with many of them) deter you from staying a part of ExPo and keeping us updated on your progress. We all learn from each others sucesses and failures (we've all had them) .

One question, I may have missed it, how many miles have you put on the fully loaded setup in the last 10 years?

 

[RunninRubicon]

YJ fun

Karma,
Gesh, what a tender subject your YJ has become! Just as a for-instence, I enjoyed my ol 88' YJ more than any Jeep I ever have owned-to include my 08 Unlimited Rubi. Why, I learned all about Jeeps in this one. Comparing mine to "the Jones" I learned to make some changes. I tossed the electric carb for a MOPAR EFI, tossed the B/A-10 after losing reverse for a built GM R700-4. Everyone tauted that the "Dana 35 is horrible." I learned this after installing both Super 30 and Super 35 kits in both pumkins. The Super 35 came with a Detroit locker and everyone swore I would break it....never did. After laying it over on it's side a couple of times I welded in a 6pt roll-cage. I loved it so I built the motor adding a 4.0L head that I ported. Crower H-265 cam, Crane ignition, headers (blue-printed and balanced the block) and multiple "bomb-proof" motor-mounts. I seemed always to ripe these apart turned 33x12.50x15 BFG MT thru 4.56 gears. I too added a hydro-boost unit out an Lincoln. No brakes in low-range! That fixed that! Rebuilt the NP-231 to include Teraflex 4-1 and a 2-low kit, short-shaft eliminator w/Tom Woods shafts f&R. After that I added an AGR pump for the steering booster and the BRAKES. Converted the A/C compressor to an air compressor and built air tanks into both the f&r bumpers. Of course a wench and a tire-carrier. It's weight grew to 4865 lbs w/ a soft top. Just over 5k w/the fiberglass top on. Painted it Alpine white with Zebra-stripes and had the license-plate stamped out to say "Zeepra."
One day after crawling around Cowboy Couple Trail outside of San Manuel, Az. I obtained some sage-brush on my cataytic converter that caught fire. I found myself standing on the side of the highway (77) w/two 1.5 lb fire extinguishers empty as it burned. The sound of a fire truck in the distance...... Drove that rig for nearly 4hrs and over every rocky trail in Az. Threw everybit of camping gear in it I had and never had issue with weight.
Build how you want it. If something breaks, improve upon it, but most of all enjoy it!!

 

[JPK]

"Gesh, what a tender subject your YJ has become!"

It ain't the Jeep.

JPK

 

[elripster]

HI JPK,
OK, how much does your JKU weigh and under what circumstances? Are you set up for a long trek? Have you actually weighed it? Most folks here have not reported actual weights. If you do not reply to this question then I'll assume you do not have a clue.

And if you had been paying attention, the wheel bearings are well under their maximum load spec. You sound like this factor has been ignored.

And if you had been paying attention, I do unload the Jeep when possible. But it's not possible on the trail on a long trip. The trailer is not there.

And BTW, it is 5200 lbs. LOADED. Are you having fun not knowing what you are talking about?

I get tired of repeating what has already been discussed.

Sparky

Wow that was harsh. Serously, you could be a bit nicer.

Karma, one thing you need to consider in trying to predict how well the rear axle bearing will hold is is load transfer. It's common in off road situations to be climbing a steep section with the axles crossed up. At this point nearly all of the vehicle's mass is on one wheel. This is part of why the off road load limits are lower than the on road limits. they other reason is the dynamic force spikes due to impacts at speed are higher and much more frequent. The bearing's working load limit leaves room for temorary spikes in load but this use model affects the bearings fatigue load limits and corresponding life. You can read up on bearing calculations... http://www.skf.com/portal/skf/home/products?lang=en&maincatalogue=1&newlink=1_0_21 if you like.


I would say crunch those numbers and see how they mesure up. Maybe you will teach us something? I admit I haven't crunched them and don't intend to because I don't have a D35 in my fleet and don't load my vehicles up nearly that heavily. If my rear axle bearings wear out in one case it's fixed under warranty and in the other the truck is 25 years old so they likley wore out due to age and advanced use. In my case a good engineer isn't going to waste time crunching the numbers unless he or she is bored and looking for a puzzle to do.

In your case you might way the time already put into this quandry against all the other technical problems you face. Maybe it would actually be more effiicent to throw a D44 under your Jeep and call it a day. Then again maybe you are enjoying the puzzle too?

Frank

 

[leaffreux]

Is my Jeep over weight

Karma
Don't go away the slide show has been fun.
:smiley_drive: