My 1985 F-350 Chassis-Cab has the plastic rear tank.

The metal rock shield has about rusted away to oblivion, except not enough gone that I can see what it is hiding.

Is that rock guard the only thing holding the tank or are there tank straps hiding behind it ?
ANSWER = YES; the Rock Shield is the ONLY Tank Support and Always Was.

I have had two ratchet-straps completely around the tank, crossmembers, and big 2x3 mud-flap hanger/crossmember for several years now and am not afraid of it falling on the road.

I am now under there and figuring out a plan of action to still support the tank in place while I remove that rotten rock guard.

Hopefully, I can slip some straps in between the guard and the tank to hold things before I remove the guard.

 

This is a chassis/cab setup. Does yours look like this?

 

Thanks for the effort; but, no, not even close.

The pictured tank looks to have big channeled L-brackets supporting it and no steel shroud/rock-guard.

The top openings also look nothing like what I have.

On closer examination of your picture, that tank mounts to the outside of the frame; not between the rails; until now, I was unaware such an animal was available on anything less than an F-700.

I have always wanted polished Aluminum saddle tanks but have never had the financial wherewithal to really get serious about it.

My tank is factory original plastic.

Since my posting of the initial question, I have been laying under there, tearing away at what will tear loose without me loosening the ratchet straps.

The rear-most portion of the shield was so rotted away that I was able to expose the entire bottom-rear corner of the tank.

With that gone, using a 1/2" socket on the heads and a 9/16" boxed-end on the nuts, I was able to remove the three bolts through the angle-brackets that held the rear of the shield to the rear rear-tank cross-member and was able to get that section gone.

Close flash-light examination through the gooseneck trapdoor revealed metal tank straps plumb across the top of the tank and these ending/beginning at a longish angled bolt through the front rear-tank cross-member.

Getting that rear section of the shield gone revealed angle brackets welded on those two tank straps and catching the two outermost bolts that held the rear of the shield --- so, from what I am seeing, even with the tank straps, sort of a ****-poor design; when the shield bolts are removed, it turns loose the straps and thus the tank.

One can't rely on the straps to hold the tank when removing the shield as the same bolts hold both = a very poor design.

If one could frequently remove the shield for cleaning/repairing, and the tank still be supported, would have been the intelligent way to do things.

Nonetheless, my metal straps are completely missing in action and as rotted away as the shield.

I am hoping to tear away enough of the offending mess to be able to catch the tank above the shield and support it while I remove my ratchet straps so as to get rid of the bulk of the shield.

On this truck at least, it would be a complete act of congress to disconnect everything and drop the tank; life will be much easier if I can keep the tank in place.

I don't think anything at all would be necessary to take the place of the shield; we have many huge plastic tanks on tractors and farm equipment that sees terrible abuse and no protection whatsoever to the plastic tanks; I believe the thick plastic is tougher than any thin metal one might put over it.

However, if any sort of rock shield was warranted, I have plenty of rock quarry conveyor belting that would make better shields than the factory original tissue-thin metal.

 

After reading your post and what I know of the rear tank setup on pickup trucks here it is.
The rear tank uses straps across the top that bolt to a cross member just in front of the tank.
This cross member is different from a non-rear tank cross member and I dont think you can make a non-tank CM work with out a lot of work to bolt in a rear tank.
Because the tank dose not sit up to the bed floor is why the top straps.

Also I want to say I remember a post(s) about rear plastic tanks and that metal shield.
Yes they all rust away from what I seen posted and I dont think anyone makes replacements
There are no bottom straps and why you dont see any only the metal shield so it is not really a shield but the bottom tank support.

It is used to support the whole bottom of the tank.
If straps were used the weight of the fuel inside would make the tank between the straps sag and over time I can see the straps cutting the tank at the edges of the strap.

If you cant get a support plate made as a replacement I would see if you can make / use straps like you want but put a plate between the tank & straps to support the tank. You can round off the edges that set to the tank so it will not cut the tank if it dose not support the full tank.

Just thinking out loud here
Good luck on a fix and let us know what you come up with.
Dave ----

 

It would be nice if you posted a few pics of your situation. My rear tank on my F250 is supported by heavy steel skid plates. These are 10 guage plates. There are two of them split down the middle. You have to take one half off, support the tank from below and then remove the other side. I used a floor jack to hold the tank up while removing the final skid plate support. Seems you have lower support straps with an additional thin sheet metal shield over the support straps. A unique situation since you have the CC frame and factory plastic tank. Post some pics as it might help someone down the road, especially of the fix. We like pictures! Good luck!

 

Yes; I can see these; and, I think I dis-connected the rear mount points of them when I took out those bolts that were also holding the rear end of the rotten shield.

If that be the case, then I will need to replace those two bolts.

This is a good point and one I had not yet thought of.

I intend to use nylon cargo straps and I had in mind five spaced evenly and running fore and aft.

Considering your points, I may now also make three straps perpendicular to the five and connected at each point they cross.

On a similar note, I bought the legendary "Feed Mill Truck"; an early 1991 Dodge/Cummins D350 DRW 5-speed that has a very interesting history all it's own.

Those model Dodge have tremendously long plastic tanks along the inside/left frame rail; 36-gallon on diesels if I remember correctly.

There are only two metal tank straps across the bottom of that long heavy tank and nothing else that I can see.

When I first got "The Feed Mill Truck", the rear strap was broken and the rear end of the tank almost dragging the ground; they had been delivering tremendous loads of feed with it like that for ages and I drove it home like that.

There are three of those vintage Dodge/Cummins sitting here and all three are like that, having only the two metal straps.

I need to crawl under one and make myself more familiar with their situation; it would probably be prudent to add a few "safety" straps under them; as, if a strap broke on the feed mill truck, it could very well break on any of them.

 

I wish I were so lucky; the shield on mine is all or nothing.

As it turns out, the straps I am seeing are only across the top to prevent the tank jumping up and out; there are no straps across the bottom; only the shield supports the tank.

What year is your truck ?

Mine is 1985.

Maybe they saw what a catastrophe having such an all-or-nothing setup such as mine was that they designed the two-piece guard.

I will say this = it is a very good thing that my tank is thick plastic; as, a metal tank in the same situation would have the bottom rusted away.

I don't know how much I can accomplish today; it flooded me out yesterday evening and is coming a monsoon right now.

At least maybe it will settle all that red rust dust under there; but then, now I will be laying in a red rust paste.

 

My truck is an 86. The tank supports are called the rear skid plate. I replaced my rear steel tank with a 19 gallon MTS plastic tank so I'm glad to have the skid plate support. Very robust.

We should differentiate between the top light guage straps which are there to keep the tank from doing the hop, and the bottom support members which are heavier guage as the hold the weight of the full tank. Some people here have said they used the top light guage strap for a tank support strap.

If you don't have skid plates support on the pickups you will have bottom support members which are 10 GA or so as well. Basically bent bar stock. You can look those up for a rear tank support and see how they are made and copy something similar. Maybe they are available for a CC with a plastic tank? Does your tank have channels in it where bottom supports would go? I think two support members should work for you, similar to the grain truck. Most likely the fastener corroded and failed on the grain truck. We do have to protect against corrosion.

 

It has two very shallow channels on the bottom that are exactly in line with the two straps across the top.

The shield actually had matching ridges.

There is a bit of the shield that is good as new laying out there calling me out into the lightning and rain like a siren on sharp rocks; I intend to measure it's thickness and post it here; I may not get an accurate measurement right now as it is probably swelled up from all the rain.

 

I wonder if the Dodge tank is thicker than the Ford tank and why only straps and not a plate?
Dave ----

 

That Dodge tank is a long way between supports as well.

The only way I would know to check thickness would be to drill a hole and measure the depth; it would be nigh impossible to get my big ice-tong calipers in and out of there with the thickness locked in.

 

The crusty shield is out and on the ground.

The back side and back-bottom corner are completely gone.

The top straps are dissolved from their rear mounting brackets to about three inches over the top-rear.

I managed to get one of the rotted top straps out in the open air; I will have to cut the other one in about three pieces to get it out.

What you are seeing is the front and about two thirds of the bottom.

You wouldn't believe the pile of corruption that fell out of there once I got those front bolts out and let it drop a bit.

When I get done, I will have to spread a few buckets of rock over the rusty mess; else, we will be tracking it in the house and in our vehicles --- loader buckets that is, not plastic buckets --- but then, I could do either as the quarry stock-pile shares a back fence with me and rock has never been a problem.

 

And that was keeping the tank in place

I have not checked but maybe LMC has the top straps?
I cant see them being different than a steel tank straps.
With that any rear tank truck top straps would work from a junk yard.
Dave ----

 

I am not going to worry about the absence of top straps as there is a cross-member that holds the mud-flaps going right over the tank; I think they were more intended for keeping the tank from falling out when you capsize.

Seven years is pretty good for me; I found my note dated October 2017 where I decided the fuel tank was about to fall in the road and I wrapped two ratchet-straps around the whole mess to prevent catastrophe.

Ford really missed the boat on their design of this set-up; of course, it may have been intentional like the self-destruct chips that companies have been including in electronic stuff so that they cease to function properly after the warranty expires.

That thin steel shield right against the fuel tank is a recipe for corrosion and a great place to trap every bit of grit and grime and Calcium Chloride that comes along.

The fuel tank has a myriad of fuel and electrical connections, vent tube, filler, etc. all connected to it and is going to always have some amount of fuel sloshing around in it.

A quick man would want to periodically drop that plate, wash it out, wash the tank bottom, and slather a bit of Rust-Linoleum Paint on it.

However, Ford has allowed no simple means of doing that; no way to prevent the tank falling out when the shield bolts are removed, thus making it a complete act of congress to do anything to prevent the shield's eventual demise.

Funny thing is, the rear tank, tucked up between the frame and cross-members and within two inches of that big Dana 70, has little chance of damage inflicted from any source; whereas, the front tank, in a far more vulnerable location, has no means of protection whatsoever.

 

Mission Accomplished !

I got these ratchet-straps several years ago at a swap meet; the guy had barrels of them for ridiculous cheap and I bought a bunch.

They are not quite like ordinary straps in that they do not have hooks, but some sort of quick-clip that engages those slotted rails one sees embedded in semi floors, walls, and ceilings.

I retrofitted them to do wrap-around style.

Although all three ratchets are the same brand, there are slight variances in their make-up; as I made them up one at a time, I didn't catch the differences until I got all three mounted; and, of course, I don't have two and one; I have three that do not match.

The bolts through the two outside ratchets are American; the bolt/nut through the center ratchet is Communist.

The straps, however, are identical.

The outside two wrap all the way around and over four cross-members; the two tank cross-members, a solid steel bar that is part of the flat, and that thick 2x3 tube that the mud-flaps bolt to.

I cut the two outer straps 82-inches and had about fourteen inches to spare.

Even after last nights power-washing, you can still see big blotches of rust stuck to the tank.




The rear side of the center strap wraps over the mud-flap cross-member and both ends then get ran through the "slot" and tightened; I was afraid maybe the slot would not be large enough to permit two layers but they went through there like salts through a widder-woman.

I needed a sewn loop end at both ends of the center strap; one at the front of the tank on my two-bolt slider thingie; and, the other end on the bolt of the ratchet.

As it worked out, the shortest double-ended length of strap I had was about a foot or so too long.

So, I made one wrap of the doubled strap on the ratchet spool to hold things in place, wrapped my too-long double-ended strap from the front cross-member around the ratchet bolt, pulled it tight and marked across the end with a big red Sharpie so I could repeat my performance on the work-bench/back of the steel flat.

I then had to disassemble my slider/loop thingie and crawl out in the daylight to make my new loop.

I used stout spring-clamps to hold the two layers together and put the end of the strap about 1/4-inch past my red mark so everything would be nice and snug.

I used my Propane bottle-torch to heat a #16 nail held with Peterson Vise Grips and melted five neat holes through both layers in a neat four points with one in the center arrangement.

On hindsight, I wish I had used a #20 nail or a #16 Common instead of Coated - a #16 Common is about as big around as a #20 Coated; the reason for wishing for the fatter nail is that the holes would close up a bit when the hot nail was pulled out and then the molten nylon would solidify such that the Copper Rivet didn't want to pass through.

Through these five holes, I inserted big Copper Belt Rivets; I washered both sides of these Rivets with drilled Abraham Lincoln Pennies; it just made me feel better.

I must have got ahold of some really good Belt Rivets as Horseshoe Nail Nippers wouldn't even try to clip them to length; I had to use my short set of Harbor Freight Bolt Cutters.

Placing the heads of the rivets on a solid no-give surface, I swelled and peened them round with a big hammer; that joint will hold 'til the cows come home.

You can't see all that work in these pictures; I wish I had taken a photo while it was all out in the daylight.







I couldn't take the center strap over the top on account of dozens of things in the way, including the big top tank opening where the gauge sender, fuel lines, and such all congregate; so, I had to get creative with that center strap.

On the front side of the tank, as pictured, I made a "slider" thingie.

I wrapped the strap, back to front as shown, around the front tank cross-member.

The sewn loop end of the strap is captured with a tubed bolt; then, it wraps over the cross-member and goes between the two tubed bolts; thus making a "loop" that can be pulled tight.





Anywhere the straps contact the edges of the cross-member, I have put slit pieces of vacuum hose between the strap and sharp edge.

The vacuum hose is thick and tough with lots of cord.





There is my brand-new axle vent whose installation backslid three Baptist preachers.





Don't that 7DMkII stand and deliver ? I can take a close-up of the smoothest girl alive and her face will look like a creek-gravel road.


The ratchets and straps are "Safe'n'Secure" brand; made in the USA.

The straps are 2-inch wide.

The tag on the straps says "Working Load Limit 1,000 lbs"

I have a bunch of the 2-inch big yellow straps that are at least three-times as thick as these; I checked the tags on them and it says "Working Load Limit 11,000 lbs"

I was tempted to use them instead; however, those ratchets are about four times as large with a huge handle swing requiring a lot more room; room that I didn't have in these close quarters.

Also, as these had that silly rail clip business on the ends instead of hooks, it didn't bother me quite so much to cut them up and make them work; plus, if I had sacrificed three of my big yellow straps, I would have had to replace them.

I have got a bunch of the big 4-inch (or are they 6-inch?) flat-bed straps and also a bunch of those rail-hanging sliding ratchets; I almost made the center strap out of one of those super-wide straps; but, I would have had to get creative in getting it snug as those ratchets are nearly as big as this tank.


I am not going to put any fuel in yet; as, my plan of action is to put a bulk-head fitting in the bottom of the tank with a ball-cut-off valve and then a length of tube with a spigot on the end so that I can set a can under it and steal a few gallons of tractor fuel when needed.

I have a valve and quick-coupler under the hood where I can couple on a hose and let the Carter Electric pump fuel into a jug or a bucket or a bull-dozer, but you had better bring your dinner as it doesn't jerk the hose out of your hand and it whip around --- but, I can get fuel that way if the need arises.

I don't brag this ability around as there are plenty around here who always run on Empty and glom onto farmers with tractor fuel in the back to give them a few gallons that they never pay for; I don't play that game; I leave them sit.