Pretty damn good idea right here. Or you could try to find factory aluminum wheels.

As far as the filter, you can also do WIX. Every bit as good as factory.

 

Stewart

 

 

I see what you mean. They almost look white. What's wrong with the aluminum ones? Did I miss that?

 

 

 

We FINALLY have a member here who potentially could out fuel Rich (Tugly) in hyperbolic metaphor.

We need to find a common topic that they both either have an aversion to or an affinity for, that would make a good drag strip for both of them to do allegorical burn outs on, and watch em run.

 

 

 

 

You're right in that the answer largely depends on the specifics of the particular truck, but those specifics stem beyond age, condition, and/or modifications. The standard and optional equipment packages also greatly effect how much the bottom of the bed will sink. Consider that factory crew cab running boards, as an example, will reduce Ford's published maximum payload capacity by 70 lbs. Those Lariat captain's chairs you added? They reduce the published payload capacity by 97 lbs. Even the factory AM/FM Stereo/Cassette/CD head unit on the Lariat reduces the payload capacity by 14 lbs.

As you can see, the weight of all the options adds up quite quickly, and this is important to remember when doing the math with Ford's specifications for spring deflection rates in order to calculate how much your bed will be lowered by the maximum rated load. Since optional equipment already cannibalizes a significant and non ignorable portion of the truck's "maximum rated load", and since the F-350's rear spring pack is variable rate, the optional equipment may already have engaged a portion of the primary deflection travel rate, when compared to the capacity specifications given for the base model (stripped of all options to make the payload capacity number larger for marketing purposes) of the F-350 crew cab 4x4 drw 172.4" wheel base that you have.

With that preamble out of the way, there is another related preamble to consider. The weight of production options (nevermind the aftermarket trinkets people add) not only cannibalize the payload capacity (or net carrying capacity) of the truck,... these options also have a weight distributive effect between the front and rear axle, and that distributive effect can also influence how much the rear bed will droop... or in this case where we are trying to guess... the influence will be in how certain specs are factored into the math to calculate the droop. For example, the factory rear hitch receiver, which is EXCLUDED from Ford's calculation of maximum payload capacity, subtracts 11 lbs from the front axle, even as it adds 49 lbs to the curb weight, and commensurately reduces payload capacity be 49 lbs. But is the subtraction of 11 lbs from the front that is of specific interest here, because it is illustrative of how mere weight alone is not the only determining factor of how much the rear of the truck will drop.

The placement of weight on the metaphoric teeter toter of the truck, with the rear axle as the fulcrum point, can have dramatic effect on rear sag, irrespective of the load itself being well within the rated capacity. Another example... the factory rear step bumper, also not included in Ford's calculation of net carrying capacity, subtracts a whopping 21 lbs from the front axle, as it adds 74 lbs to the curb weight (and reduces payload capacity by 74 lbs). So just the receiver hitch and the rear bumper, which most people would consider to be standard equipment on a pick up truck, lifts 32 lbs off the front axle, or in our metaphor, is like the kid on the front end of the teeter toter losing 32 lbs. What does that do in terms of influencing the truck's rake or stance? You get the idea.

There is yet one more preamble related to optional vs standard equipment to cover before we get to the number below. In between the 99, 99.5, and 2000 model years, there could be three different sizes of spring blocks on F-350 dually vehicles, depending on when built, and depending on if modified by Ford at a dealer after the fact of manufacturer upon customer request per a TSB, and depending on if later modified again per one of two subsequent TSBs, based on customer request or the success or failure of the earlier TSB. This gets kind of complicated, but I'm going to get into it here a little bit to help you sort it out, since you may be noticing a difference in rear suspension ride height between your 99 and your 00.

If your 99 was built on or before Valentine's Day in 1999, then it might have 4" rear spacer blocks under the spring stack when it left the factory. But the original owner might have complained that the bed was too high to back under a 5th wheel trailer to pull it. A lot of folks complained about this back then. I heard their complaints in real time, as I was on the RV forums back then also, just like now. Only back then, it was like being on the 2017 and up forum... everything was new. It was new to Ford too... and Ford made an effort to address the concern by issuing TSB 98-17-02, which directed dealers to remove the 4" spring blocks for customers who complained that their trucks rear bed was raked too high for towing. This service was done under the original warranty, for those who qualified. It is quite involved, removing those blocks. It required new ubolts, new nuts, new shock absorbers (from the 4x2 model), new brake lines, new carrier bearing support bracket and shim, new rear stabilizer bar, new rear stabilizer bar links... and labor to get all that done, including bleeding the brake system and re-adjusting the headlamps. I thought that was quite a step up on Ford's part to meet their customer's expectations to be able to tow. After all, that's more often than not the entire reason they bought a crew cab dually... to be able to tow a big 5th wheel or gooseneck trailer. Beds that were too high could never have enough clearance between the bed sides and the overhangs of gooseneck and 5th wheel trailers. Ford missed this on the original 99 up design, but at least was responsive after the fact.

However, THAT first field fix didn't work. The trucks that had the blocks entirely removed per 98-17-2 were now TOO LOW in the rear once loaded. They were bottoming out. So a new TSB was issued (99-9-5) to install 2 inch blocks when removing the 4" blocks for pre-Valentine's Day 99 model year trucks that hadn't yet been modified per the earlier TSB, and to add 2" blocks to those vehicles that were already modified by the earlier TSB. As you can imagine, any block changes required new U bolts, new flange lock nuts, new shocks, new stabilizer end links, new carrier bearing shim etc. Some of the parts changes are wheel base and model dependent, so it isn't like all trucks were modified with the same parts, because obviously driveline angles differ based on wheelbase and rear GAWR. Later on, a third TSB was released (99-14-5) which superseded 99-9-5, clarifying applicability.

If your 99 was built after Valentine's Day 1999, then it came from the factory with 2" blocks, and was not eligible to have them removed on Ford's dime. But, owners who missed the "look" and "stance" of the early 99 trucks that they saw when they made their decision to order one, and where disappointed by the time their truck arrived (if built after 2/14/99) would sometimes buy all the take off parts from trucks which were lowered, so that they could "lift" the backs of their trucks using all Ford factory parts, and use an aftermarket leveling kit in the front. Given that your 99 had ridiculously large tires on it when you bought it, there is a possibility that a previous owner may have lifted that truck in this manner, and you would be hard pressed to tell the difference if all factory parts were used in the rear. All the parts will have aged the same, and if the parts were take off production parts, they would not have any FCSD service part designation on them either, only the engineering number. That's the trouble with buying used vehicles with nearly 20 years of history... you never know quite what you are dealing with.

Ok, with those three preambles out of the way, here are the numbers.

For a 99-01 F-350 Crew Cab 4x4 dually long bed 172.4" wheelbase, the rear axle rating at ground is 9,750 lbs, but that includes the unsprung weight of the axle, brakes, and four tires and wheels. Ford states the rear leaf spring capacity at ground for the F-350 DRW is 8,250 lbs. There are five leaves in the main pack, and one auxiliary spring. The auxiliary spring has a higher rate of deflection than the main pack, which contributes to the variable rate of the spring assembly. Prior to the auxiliary spring being engage, the main pack has a deflection rate of 350 pounds per inch per spring assembly. So the first 700 lbs tossed into the back of the bed would deflect the springs an inch (but keep in mind the first two preambles above... how much deflection has already occurred from optional equipment, and the location of said equipment). Perhaps the next 700 lbs of weight in the bed would deflect another inch. So there is your 2" right there, with just 1,400 lbs.

This would not surprise me, as Ford rear springs are known for their pronounced rear deflection... soft springs to achieve a car like ride... a mantra that Ford has been focused on for at least the last 50 years. In fact, here is an advertisement from 50 years ago...



Ahhh... I'll bet your eyes needed a break from all those preceding paragraphs of text didn't they?

Ok, back to the grind at hand. Once the auxiliary spring engages, the deflection rate changes along with it. By itself, the auxiliary spring deflection rate is 518 lbs per inch per spring. But in combination with the main spring pack, the deflection rate of the assembly becomes 730 lbs per inch per spring. So at the point where the springs that were previously deflecting 1 inch down for every 700 lbs tossed into the bed, once the bed sinks enough to engage the auxiliary springs, it will take 1,460 lbs to sink another inch.

At this point, the question of how many pounds can be put into the bed arises. As stated in the preamble, this will depend on the optional equipment the truck is loaded with already, since Ford cites specs in the most favorable light possible, which means the barest bones equipped truck as possible in order to claim the highest capacity number possible, even if the using the lighter gas engine for the reference truck. The Maximum Payload Capacity for your truck can range from 3,900 to 4,400 lbs, with 4,250 lbs as the specification reference point most cited. In your case, I think the payload capacity will be less. Heck, you lost about 75 lbs capacity switching to all steel wheels.

At the "car like" rate of the variable rear springs, 350 lbs deflection rate per inch per spring means 700 lbs (considering both left and right springs) might drop the bed an inch. At the "truck-like" rate of the variable rear springs, 730 lbs deflection rate per inch per spring means it might take 1,460 lbs (considering both left and right springs) to drop the bed another inch, once the auxiliary spring is engaged.

700 lbs deflection first inch
700 lbs deflection second inch
1,460 lbs deflection third inch
1,460 lbs deflection fourth inch...

Add them all together... 4,320 lbs likely means about 4 inches of rear deflection... or about twice as much deflection as the 2 inches max you initially thought.

Yet to be fully considered in all of this is the distribution of weight either ahead of, or behind, the fulcrum point represented by the center line of the rear axle. We all know that weight placed behind the rear axle will cause more rear deflection, with less weight, where aft of axle weight unloads the front axle....than weight placed ahead of the rear axle, where part of that weight is borne by the front axle, which partially sinks together with the rear axle, maintaining more of the same "muscle car" rake ratio as the truck's initial stance when unloaded. That probably needs no further explanation.

The original bed deck height, with factory tires and wheels and blocks, was 37.3" from the ground.

 

Wow! Incredible writeup!

Not to hijack, but first another point of reference and a related question. My '03 F-350 SRW with 3600 pounds in the bed has a reverse arch on the main rear spring packs, but the auxiliary spring is only engaging one of the stops, not both (the front stop still has a half inch of clearance).

Setting aside the front axle limit and GVWR, considering only the rear springs...

I would like to know, independent of SRW vs dually, F-250 vs F-350, 4WD vs 2WD, engine, or other equipment, if there is a good rule of thumb for "reading" the rear springs with a load? For instance, does a reverse arch on the main spring pack indicate an overload regardless of truck specifics? As you pointed out above, any optional equipment affects payload. But that weight preloads the springs, so it seems there would still be a maximum deflection at maximum load (assuming neither front axle or GVWR limits were already reached).

From what I have seen on my truck, fully engaging the auxiliary spring would be an overload on my truck. The rear suspension is bone-stock. And I do not have a yellow sticker on my door jamb for reference. But the reverse arch does not look good, even though the auxiliary spring is not fully engaged.

 

 

You're right... this is a thread hijack. It might be better if you started your own thread, but you've already got a half dozen threads open on your truck already, so it is understandable why you wouldn't want to open yet another.

Nevertheless, without the context of your specific truck, it is hard to accurately answer your question... because you can't pick and chose what relevant facts to ignore. In your question quoted above, you want to ignore your front axle and springs, you want to ignore your truck's GVWR, you want to ignore that your truck is an SRW, and you want to ignore all the other optional equipment has, as well as what engine it has. Yet all of these factors are relevant facts in answering your question about the negative arch you are observing with your rear springs, even while your overload springs is not engaged on both frame tabs.

Yet, the one aspect in all of this that you should be ignoring is the negative arch, because there is no rule of thumb for reading leaf springs by a visual assessment of their arch, empty or loaded. Next time UPS or FedEx rolls up at your home or business, have a look at the front and rear springs of the medium duty walk in step vans that they drive. Quite often, the leaf springs will be flat, or "reverse arched". Right now I'm looking at a 2001 crew cab F-750 in the yard outside my window that has an empty flat bed on it, and the rear leaf springs are flat arched. My old '79 F-250 had negative arch leaf springs up front. In leaf springs, neither wear nor capacity can be determined by arch alone. There are too many other factors, including but not limited to leaf width, thickness, material, heat treatment, length, number of leaves, etc. There are, however, other areas to examine to help diagnose if the springs are either worn out or working beyond their capacity.

However, a lot of the areas that need to be examined are the areas you wanted to ignore at the outset of your question. But let's briefly look at them anyway, because that's the only way to get closer to a useful answer. Let's start with the least likely thing that would seem to make a difference... the engine. You've got a 7.3L. This makes a difference, because Ford has an entirely different set of maximum payload capacity ratings for the 7.3L, and counter-intuitively, those ratings are almost 1,000 lbs LESS then that of a gas engine equipped F-350 crew cab 4x4 single rear wheel long bed such as what you have. So, if you were to look at Ford's advertised maximum payload capacity for an F-350 CC 4WD 172 WB, you might see 3,750 lbs max payload. With this number in mind, you might think your 3,600 lbs payload is well within range. But that spec isn't for the diesel. The max payload for that same truck with the diesel engine is only 2,920 lbs. So, you are already overloaded by almost half a ton, and that doesn't account for all the factory as well as aftermarket options you have.

Which leads to the next ignored item that would seem the least likely to make a difference. Your aftermarket bumper replacements, both front and rear. Your all welded steel front bumper replacement with an integrated cow catcher bull blocker grill guard, by itself likely weighs 200 - 300 lbs, but it isn't by itself... it also appears to have a winch built in. And then your sturdy steel rear bumper likely weighs at least 100 lbs. Would it be fair to say that the aggregate of just these three items of aftermarket equipment adds 500 lbs of mass to your truck? Then subtract that from the maximum payload capacity, leaving you with only 2,400 lbs payload, without accounting for any factory options that your truck may have, which Ford did not account for when determining the rating Ford advertises, but which Ford asks us to account for, when determining how much weight our trucks can safely carry.

Ford asks us to do this by first telling us what the Maximum Allowable Weight of their regular production options, plus our aftermarket equipment options, should be. For the F-350 CC 4WD LB, the Maximum Allowable Weight of all options, stock and aftermarket, is limited to 1,638 lbs. The 7.3L engine with a ZF6 consumes 672 of those pounds. With an auto, use 631 lbs. For rough figuring, since I don't remember what transmission you have, call it 650 lbs, leaving you with 988 lbs for factory options and aftermarket equipment. Now subtract your 500 lbs worth of hunky steel end caps with a winch, and you are left with 488 lbs for the remaining options your truck might have. Got A/C? Subtract 41 lbs. Got XLT trim? Subtract 93 lbs. Got "Off Road Equipment" package (ie transfer case skid plate)? Subtract 68 lbs. Got a factory receiver hitch? Subtract 49 lbs. Let's stop there for a minute and just add those 4 items up... 251 lbs of factory optional equipment. So that leaves just 231 lbs left to stay within Ford's Maximum Allowable Weight of regular production options and aftermarket equipment, and we havent even discussed towing mirrors, or your aftermarket thick steel 19.5" wheels and oversize tires, or all the extra leaf springs in your 4" lift kit.

Which leads to the next item you wanted to ignore... your front springs. They are not only not stock, they introduce a 4" lift to the front of your truck, which shifts the factory rake of your frame upward. An alteration in the rake angle of your frame can effect the engagement of your auxiliary rear spring. Even if nothing was changed in rear springs, the angle of the frame to the ground has changed, and the rear axle is still stuck on the ground. Not only are the pinion angles altered (evidenced by the destroyed carrier bearing you earlier reported), the rear leaf springs are engaged differently when heavily loaded due to the alteration of the frame angle. And you are not just heavily loading your rear springs at 3,600 lbs payload... you are overloading them, significantly, considering that you are already exceeding, by nearly a half ton, the maximum payload capacity of your truck, that in and of itself is reduced by another half ton from the weight your factory and aftermarket options.

But there are yet more specific facts about your truck that could potentially effect auxiliary rear spring engagement and main pack arch settling. Your truck was rear ended. Your rear spring packs were altered (my estimation from one of your photos in another thread). Your front end is higher (from aftermarket spring pack). Who knows what else is going on there? And we haven't even discussed where the center of gravity is on this 3,600 lbs of weight you've been talking about (truck camper? pin weight of 5iver?).

In summary, you would be best served by incorporating this question into one of your own threads about your truck, and work through all your concerns within the entire constellation of the many other issues you are trying to simultaneously sort through, so that any meaningful recommendations can by informed by the context of what you are working with. I only answered here because I didn't want you to feel ignored, and because your question did indeed dovetail as another example illustrating the impact of aftermarket as well as optional equipment on vehicle manufacturer's advertised carrying capacity ratings. I kind of wish manufacturer's were forced to disclose the carrying capacities of fully optioned trucks as typically ordered, rather than as barebones vehicles so that they can bamboozle consumers with a numbers game against the competition.

 

Actually, I have a thread with this question specifically related to my truck. Did not get this answer in that thread, so I do thank you for taking the time here. I was trying to generalize the question in the context of this thread and separate it from my case rather than focus on it. I clearly did not succeed in that endeavor.

I may take a few parts of your reply and wake my other thread back up. I already came to the conclusion there that I was overloaded at 3,600 pounds, and maybe did not make that clear here. And I suspect it is in great part because I am over GVWR (7.3, bumpers, winch, XLT).

I do understand I can not pick and choose which limits to go with or ignore on the road; any limit is a limit, even if other limits are not reached.

In terms of the general question I was trying to separate out (reading rear spring), your greater knowledge shows that the answer is "no, there is no way to read the springs to observe that the rear axle is over limit." For that I do thank you and if I have the time to go back to my earlier thread, I will start with that thought.

I now wish to return this thread fully and completely back to the OP.