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Old 08-11-2017, 02:53 PM   #1
Mryan
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2003 Seats in a 71 4x4?

Has anyone installed the seats from a 2003 Chevy truck specifically the 40,20,40 with the "jump seat/center console" in a 67-72 4x4? I want to switch and found a nice donor but am unsure if they will fit. Thanks
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Old 08-11-2017, 09:06 PM   #2
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Re: 2003 Seats in a 71 4x4?

Integrated belt seats require significant floor reinforcement to be safe. Stock floors are not designed to handle the loads the seat will put on them in an accident. Our cabs are built to take the seat belt loads in tension at the rear floor and tension from the B Pillar. Integrated puts compression forces into the floor that they simply aren't designed for.
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Old 08-12-2017, 12:29 PM   #3
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Re: 2003 Seats in a 71 4x4?

Any tips on supporting the floor sufficiently then? The stock belts attach to the floor so I find it hard to believe that the floor isn't sturdy enough...
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Old 08-12-2017, 02:33 PM   #4
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Re: 2003 Seats in a 71 4x4?

I never even considered this. Maybe because you are not just dealing with belts and a person, but you are dealing with the mass of the seats themselves and the person? The trucks have specific reinforced mounting for the factory seat belts. The seats just have the plain metal floor.
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Old 08-12-2017, 04:44 PM   #5
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Re: 2003 Seats in a 71 4x4?

I would think if you reinforce the floor where the seat mounts you would be ok. Fabricating skills would be needed.
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Old 08-12-2017, 05:41 PM   #6
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Re: 2003 Seats in a 71 4x4?

I think creating a simple box under the floor that spans the original belt mounts would be plenty strong. The engineer the mounts to hold the weight of pretty large people, so unless you are like 350lbs I wouldn't worry about it. Much more detrimental to safety would be the lack of crumple zones, airbags, etc -- I'm going to put a roll cage in mine so that I won't have to worry when my kids drive it. Sorry, a bit off topic!
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Old 08-14-2017, 11:29 AM   #7
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Re: 2003 Seats in a 71 4x4?

I design seat and seat belt installs in RV's and have for 20 years. Though I've broken a sweat a couple times I've never failed a test. That's not the norm. My instincts are pretty good. The floor is NOT strong enough. The stock bench floor is not strong enough for stock buckets with no integral belts if the truck didn't originally come with them in 69-72. Integral belts put all of the load to the seat mounting points not the seat belt mounts. The seat adds considerable mass and therefore loads. On top of that pulling the shoulder belt at the seat top is a lever that tries to push the front of the seat down through the forward floor. Stock belts only pull in tension from the respective factory designed points. OE seat mounting only needs to be strong enough to keep the seat itself in the truck. The stock belts only keep you in. If you'd ever seen destructive testing of this stuff you'd heed my advice. I'll note that this topic comes up over and over. I post up the same info every time. Most of what I've seen done for this I wouldn't bet a life on.

I'll not offer opinions as to what will make it safe. Personally as much as I like the seats I wouldn't use them. If I had to I'd start with a perfect rust free floor and add significant structure at the front and some at the rear. Beyond that you are on your own. A pull test to certify a single 3 point belt at the back of a 3500 series van can lift the back of the van off of the ground. It can also collapse a van floor and can pull the rear pillars in.
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Old 08-14-2017, 12:09 PM   #8
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Re: 2003 Seats in a 71 4x4?

I'm probably going to go with the integral belt seats, but also want to make sure it's as safe as reasonably possible.

Adding bracing seems like the only way to add strength, but you mention bracing the front more than the rear. At the same time, the lever action of the shoulder belt will put more stress on the rear mounts. So why not brace the rear more than the front?

Additionally, what are typically the best mounting points on the cab for the bracing that will withstand high impact forces? I'm thinking that bolting down through the floor and into a square tube crossmember that sits under the frame lip would be best but then maybe the attachment would be *too stiff* -- having some give in the metal to absorb force during impact is probably a good thing, to some degree.

A lot of guys are going this route and getting an example of a sufficient mount from a safety perspective is likely to save someone from injury, or their life.
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Old 08-14-2017, 01:19 PM   #9
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Re: 2003 Seats in a 71 4x4?

In the stock cab the front floor only has to hold onto the seat in a forward crash. All of the load you impart is onto the belts in tension is on designed mounting points for that purpose. When you pull forward on the upper belt at the seat top you are trying to force the front seat mountings through the floor. It was never designed for that. 69-72 trucks that had buckets actually had bracing just to support the buckets. Clearly the front floor isn't sufficient to resist the forces if it isn't sufficient even when seat belts aren't integral. The rear floor area has a cross member and huge rear cab supports, back panel and B pillars that can handle the tension loads. Tension loads are like on a rope. Compression loads that try to push through and puncture the floor are an entirely different animal. Do you want to be in that seat as it rolls down at the front and submarines through the floor? You'll get intimate with the steering column on the way by and the passenger with the dash and glove box. I could give you more advice but I'm not going to be the one that gets sued when it's interpretation and application are not as I intend. We test this stuff and it costs a lot of money to wreck a body and find out my instincts were right. Think like its a race car floor and treat your cab floor like your life depends on it because it might. Stay with the stock belt mounting and things are very simple. Integral and things are ugly. We avoid integral like the plague.

You don't want to rigidly connect your cab to your frame with the seat and belt mounts. You can install towers on the frame or cab bottom that provide resistive compression points that forces from the cab can be directed into after a small amount of deflection.

You either do this stuff way overkill or spend a huge amount of cash leaning it all out or building it up until it's just enough. Overkill is a good strategy in low volumes.
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Old 08-14-2017, 02:04 PM   #10
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Re: 2003 Seats in a 71 4x4?

I understand that you don't want to provide suggestions for an implementation due to liability. Can you instead point to a good example implementation in a production vehicle that we could look at for inspiration?
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Old 08-14-2017, 03:41 PM   #11
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Re: 2003 Seats in a 71 4x4?

Look at the vehicle you take the seat from. Material shape is very significant in overall strength of the floor. More shape and depth of that shape are typically stronger. Note material thickness, gussets and reinforcements. Also consider that the floor is most likely high strength steel which our floors are not. In reality our floors will be so different that none of what you see will likely be a good guide but start there. The rockers in a perfect rust free 67-72 truck are likely your starting point. Bridging those appropriately is also likely a good path to look into. The front floor area where the cab mount bolts go through is a very robust part of the floor but a bit far forward. You need the main reinforcement very near where the front seat mounting points are.

If there is not enough room to go down towards the frame then go up into the cab with your structure. Bolted connections are not out of the question depending how they are executed in your system. You can also have some structure below the floor and some above.

There are so many other options for donor seats. I don't get why people just don't go another direction.
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Old 08-17-2017, 12:50 AM   #12
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Re: 2003 Seats in a 71 4x4?

Thanks for the ideas, I do have a Suburban with these seats and I'll take a look at how they mount.

In general these seats seem to fit well, look nice, and the integrated belts are a bonus. A lot of people are pull LS engines out of these trucks and doing so by purchasing wrecked vehicles, so the seats are basically free.

Integrated belts is actually the single biggest reason I wanted to use these seats -- it just simplifies and cleans up the entire installation. I suppose I can rethink this now, and maybe it makes sense to take a look at using the stock mounting points but I have doubts that the stock shoulder mounting point has much strength compared to the integral belts.
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Old 08-17-2017, 11:07 AM   #13
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Re: 2003 Seats in a 71 4x4?

The stock belt mounting points are intended for seat belts and are designed for such. Everything is in tension and very simple. NOTHING about integrated belt seats is simple and nothing in the truck was ever intended to handle those loads. Yup you wanted to use them I get it. It is possible to do it too. 99% of what I've seen however I wouldn't even let the people I don't like ride in. Frankly in most of them you'd be safer without wearing the belts. You keep making statements in disbelief. Go ahead and put them in then. If there is a problem you will know when there is a tragedy.

We've all seen these seats in a thousand trucks right? That should make it ok right? Nope.

I wouldn't attempt a pull test expecting a pass on one these seats in a 67-72 without significant alterations to the floor. I will reiterate. 69-72 truck floors are not strong enough to even mount stock 69-72 buckets to. Bucket trucks had extra floor reinforcements. If the floor can't safely support stock buckets how are the huge loads added by a human being attached to the seat and multiplied by leverage suppose to be handled. And that's just one person. The floor has to potentially handle that by a factor of 2 or more.
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