Double Truck Frames

showcrop

Well-known Member
Many of us have first hand experience with bad rust damage of frames of trucks with double frames, primarily in the northern states. I know of trucks getting new frames due to the rust. I had a truck with a double frame, and I had no evidence of any rust problem. I used to spray WD-40 along the top between the edges, as well as wherever there was a hole punched in one but not the other. Does anyone know of intervention that can be performed before damage gets serious, besides just spraying oil? I already know of at least two places that spray oil. This is for a fifteen year old fire truck.
 
I can't answer your question but I know first hand what happens when the double frame rails rust. Our fire dept. bought a 1974 GMC 4,000 gal milk tanker. We equipped it for fire service use. Because we are rural we used it to fill swimming pools as a fund raiser. One year we hauled somewhere around 900,000 gal of water.
Eventually the rust between the frame rails got so bad that the outer rails buckled and became wavy to the point that it looked like the heads of the bolts were going to pop off. We had to replace the outer rails which was a lot of work because the tank had to be removed.
You are going in the right direction to protect the double frame, I just don't know what really works.
 
When I worked at a dodge dealership they
had a rustproofing program for just a few
more bucks. They had the black undercoating
(which you can buy at O'REILLY auto parts
in an aerosol can) and they had a scours
yellow tar like substance that they
squinted up in the doors so it would ooze
down and protect the door seams supposedly.
I don't know if they still use these things
but I would check into those products.
 
(quoted from post at 17:57:09 07/24/17) When I worked at a dodge dealership they
had a rustproofing program for just a few
more bucks. They had the black undercoating
(which you can buy at O'REILLY auto parts
in an aerosol can) and they had a scours
yellow tar like substance that they
squinted up in the doors so it would ooze
down and protect the door seams supposedly.
I don't know if they still use these things
but I would check into those products.

Greg, I know that both of those products are flexible, but I don't trust that type of product because the moisture can get behind them. Then moisture does not get exposed to the air, so the rust is eating away at the metal 24-7 instead of just a few hours until it dries out after getting wet.
 
I've heard a couple of different things in the past about the reason for double frames. Besides when making repairs, it seems as though there was a time when manufacturers would use a double frame for a heavier-duty truck - like, a SA tractor might have a single frame, but a heavy haul rig would have the same frame doubled for extra strength. Sounds kinda weird to me, but then I think I learned that online......so you KNOW it must be the truth! 8)

The other thing is, that sometimes a truck with a particular purpose will need a doubled frame as all of its load is concentrated in a certain area, rather than being distributed over the entire frame. ...Only possible example I can think of offhand might be a dump truck, but I would tend to think they would have their own special frames.

If nothing else, just consider this post as "Junk Mail". :lol:
 
If you continuously spray WD-40 between the rails
(like every 6 months), I think that would go a long
way to preventing rust. I don't know how common it
is down there, but up here there's a company by the
name of Krown that rust proofs vehicles with a drip
type spray. It really creeps and gets into every nook
and cranny. I'm not a fan of drip less undercoatings,
because they naturally don't creep as well. I really
dislike coatings like Ziebart, cause all they do is trap
moisture and really make things rust.
 
My son swears by Fluid Film he has been using it on all his vehicles and his 94 Ford F-250 looks pretty rust free from what I can see. I just started using it on my vehicles this year I spray it inside the doors, tailgates and rocker panels then the entire under side the best I can, Time will tell. I bought the spray gun and attachment tubes from them as well.
 
Sounds like you are on the right track. I have wondered about this too as the DM Mack I used to drive for my long time friend and farmer had serious issues with this on the double frame. It was a ready mix truck at one time, heavy spec truck, very hard riding truck. The outer frame member was fractured by the built up layers of rust, I can recall him having the frame repaired at least 2 times. Mechanic said if you see these layers of rust, get a hammer and knock them off before it expands too much. I really had never seen such a thing on a truck frame before.
 
You're never going to prevent rust, only slow it down. You can spray whatever coating you want but you can't get it everywhere. One little pinhole in the protection is all rust needs to get started, and it will be somewhere you can't see, can't reach, and when you finally notice it, it will be too late.
 
(quoted from post at 05:18:32 07/25/17) You're never going to prevent rust, only slow it down. You can spray whatever coating you want but you can't get it everywhere. One little pinhole in the protection is all rust needs to get started, and it will be somewhere you can't see, can't reach, and when you finally notice it, it will be too late.

Engineer, I agree with part but not all. Rust requires moisture and oxygen. It is possible to reduce the moisture to the point where rust cannot take place. It is just a matter of a combination of adequate coverage of the area and adequate frequency. Both take time and money and one has to balance how much of each to spend against the importance of the desired outcome.
 
WD-40 does not work very good for rust prevention.

Fluid Film is now my first choice. I sprayed some in my car doors and hood channels. Been a year now and on these hot days it creeps out and climbs up the doors on the outside too as you can see the dust stick. It stays soft and creeps !
 
Put a Detroit Diesel 71 series engine in it. Just joking, but reading your post reminds me of something an old friend once told me. When I lived in Illinois one of my friends worked on city buses for the CTA or RTA. He told me that the old reliable 71 Series Detroits used to sling oil all over the place, and the biggest problem that they had after Detroit went to the powerful 92 Series platform was that they didn't sling oil all over the place, so the bus frames used to rust out around the engine compartments due to road salt build up and damage. So................put a reliable and powerful 71 Series Detroit in it, multiple problems other than fuel economy solved, so I've heard.

Mark
 
(quoted from post at 06:27:14 07/25/17) WD-40 does not work very good for rust prevention.

Fluid Film is now my first choice. I sprayed some in my car doors and hood channels. Been a year now and on these hot days it creeps out and climbs up the doors on the outside too as you can see the dust stick. It stays soft and creeps !

What do you do about the moisture that is deep down in between plates or sheets of metal. Will fluid film displace the moisture and creep in five inches where the metal is pressed tightly together and rust is in between trying to expand?
 
The guy that says never own a double frame truck is only partially right.
The deep single frames are great until you get to the real long wheelbase trucks. Then, if you are hauling heavy loads you'd better have a double frame. Although I've never seen one, I've heard of ultra heavy haulers having a triple frame.
DWF
 
Try to get the frame well dried off... then apply Krown or Rust Check. Krown would be my first choice. We had that done on one here and it
stoot up for quite a while considering it's in a heated barn 99% of the time...
Then, in 10 years... make sure the next one has a deep single frame...

Rod
 

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