Is there a reason modern trucks don't come with fully sealed frames to prevent rust?

Lol learn something please. No design, of anything, is perfect.
Box frame has some advantages over channel frame.
Channel frame has some advantages over box frame.
Unibody is even more rigid than box frame and that has some advantages as well.
None of them is perfect for every circumstance.

From a design perspective, channel is much better for handling live loads.
Box can handle some loads and will give you better handling and ride.
Unibody is even better than box for handling and ride and still handle some loads.

They all will rust without any protection if made from steel.

 

What an absolute douche nozzle comment

 

I understand you, you said you didn't think the "sandwiched" frames were effectively worse.
I attempted to show you that opinion was incorrect, and didn't assume you were saying sandwiched frames are great.
Sandwiched frames die a quicker death and also are harder to patched properly than a single layer boxed frame. In the video, the increased rust is clearly visible around the edges of a sandwiched plate.

The difference on your GX is it's a Lexus, and I also own a Lexus, an RX330, that has done 17 years and 215k in Buffalo that is remarkably barely corroded, even its painted steel subframes.
I would bet Lexus uses the best coatings over and above Toyota badged vehicles.
Also it may be Japan uses better coatings than the EPA allows in the USA, so Japan built may increase corrosion resistance.

 

Boxed sections don't twist nearly as much as open sections. If you need your frame to twist and flex then you did a shit job designing your suspension.

Stiffness, twist, strength, and impact behavior can be fully engineered regardless of the approach taken. Almost universally the boxed frame will be lighter, but more complicated to manufacture.

 

The conversation is about rust, not really stiffness.
It's been asked before and spoke of (pretty sure court documented) that the flaw was in the steel specs set forth by Toyota to Dana.
All it would have taken was a bit more Chrome mixed in and we wouldn't be sitting here talking about it.
Toyota never wanted their trucks to last forever.

 

Don't know about japan but vehicles made overseas by mercedes and bmw the frames are coated with cosmoline to withstand the salty air journey before they get to dealers here in the u.s.

 

Stiffness aside. A Zinc galvanize treatment on the frames would assure longevity well past 30 years in nearly all regions of the USA.

Planed obsolescence is the only reason why Zinc treatment is not done.

 

I remember years ago when Ford had a comercial on in which they showed their Truck frames being hot diped gavanized, it was on every evening about five times. Also, I remember there was one about their "Twin I Beam suspenstion".

 

That makes sense. I've oftened wondered why Toyota would put all this great product development on a fundamentaly flawed platform. It's like building a house on a mushy / weak foundation.

 

Twin I beam suspension? That goes back some. Back around 1966 i drove a 2wd ford F100 for a shop i believe that had it....biggest pos i ever drove to this day.

 

Yup, but the roads are always slushy and wet anytime theres salt on the roads. Id think that would be enough..? As opposed to being fully submerged in water like a ship. But Im not sure

 

Just too bad the full sizers from the big 3 will completely fall apart in other ways. Body rust out, interior bits break, electronic stuff quit working, engine/transmission puke out around 200k. I agree the frame will be in better condition on its tow to the junkyard compared to a Tacoma though.

 

I don't think it's all planned obsolescence. Consider Toyota had to implement several frame replacement programs. I think it comes down to cost engineering. The paint they use is thin so they don't have to chase the threads on inserts. It's cheaper to form one chunk of plate into a channel than to form two and make several very long welds. And if they do choose to do a boxed frame, it's easier to add drain holes than fully seal it.

For strength to weight and stiffness to weight (and often impact energy absorption) you can't really beat a boxed frame.

For low cost you can't beat an open channel.

Both can be made to have no corrosion issues, and both can be made to have equal flex, strength, and impact energy absorption. But the boxed frame will be more expensive and the channel frame will be heavier.

Hybrid frames are often made because some parts of the frame need to be stronger and more rigid, and so they just weld another channel opposite the first one, because it's impractical to splice together different thickness channels. Changing the channel width and depth does alleviate this issue to some extent.

 

Yes this will happen, I was surprised at how well those full size frames did considering the conditions.


I have seen Toyota frames that are several decades old that still have life in them.

 

My brother owns a 2005 astro van as a secondary vehicle. He just got that great gm feeling again when the fuel pump took a shitter...before that it was 2 relays that control the headlights and interior lights....and before that the rear door latch broke. He just replaced the battery and did the brakes. Now afraid to guess what could be next. This vehicle has only 49k original miles.

 

We had an Astro Van at my old work as a Site Vehicle, what a hunk of shit that thing was. You had to enter and exit from the passenger door as the driver's door was broke shut. It shook and vibrated so bad and you could hear the rear diff screaming for its life. All kinds of electrical gremlins as stuff just turned off and on whenever.

 

I don't know anything about anything. Could frames be made from titanium? I assume it's way more expensive, but would that make a good frame?

 

Titanium has decent corrosion resistance but is very expensive. Also, while being very strong for it's weight it is much bulkier to get the same strength and also much harder to form.

Like aluminum, it is prone to fatigue cracking when flexed repeatedly, so steel really is a better option here. Various alloys of stainless steel could do just fine (with no weight penalty), but so could better coatings or frame design.

 

Titanium is about 30 X more expensive than steel!