Driver and Passenger Seat Options / Swivel Bases / Seat Belts

Matt Colie

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Oct 25, 2019
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This has been a really interesting thread and as a guy that spent some time in OE crash testing (two rounds actually), I applaud your interest. There were crash test standards for driver and front seat passengers in the '70s but those were very different than those now.

There was a tragedy this spring. TZE crashed and caught fire. The couple in the front seats could not escape. This might have been because they were both unconscious as a result of the impact. We will never know.

There is one thing you might think about, there have been two coaches rolled. The occupants survived both cases. There are pictures somewhere of the best example because the driver and passenger were still belted in their seats, but the coach was GONE above the belt line. (So, I might advise against anchoring to the B pillar.) Admittedly, TZEs are really hard to roll, but it could happen again.

And, Always marveled how fast flight attendants could pull out that jump seat and get hooked into that five point harness.

Matt
 
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tmsnyder

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Oct 7, 2019
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I'm replacing seats and using either the original lap belt or a replacement lap belt with the original anchor locations. The whole question of getting those anchors correct as a DIYer is not a can of worms I want to open up. I'll just use the ones the smart GMC engineers intended, even though safety in '76 was a lot different than safety in '19.
 

Mike Perez

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Oct 2, 2019
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I'm replacing seats and using either the original lap belt or a replacement lap belt with the original anchor locations. The whole question of getting those anchors correct as a DIYer is not a can of worms I want to open up. I'll just use the ones the smart GMC engineers intended, even though safety in '76 was a lot different than safety in '19.
Those anchors are nothing special. As long as you’re going to use only lap belts without them being integrated into the seats, there’s nothing wrong with the factory base and mounting locations.

All they are is a piece of 1x3 flat bar with a large nut tacked on and a couple of screws threaded through the aluminum to hold them in place.

E4348D3C-6BEF-42FF-A291-423AA5B2D6E0.jpeg2F1B8490-6C4D-4F25-B16A-7569D1A0351A.jpeg
 

tmsnyder

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Oct 7, 2019
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Mike I'm sure they are nothing special but I'm also sure they were engineered that way.

Matt, that GMC that crashed and then burned, wasn't there some question as to whether they had installed an electric fuel pump without an inertial shutoff switch? It may have also had some sort of homebrew surge tank of gasoline installed near the engine. They may have survived the crash only to be burned alive by their own gas which kept on pumping.
 

MikeB

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Oct 26, 2019
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... I'll just use the ones the smart GMC engineers intended, even though safety in '76 was a lot different than safety in '19.
Not to sound like a hater but there are more than a few things about this GMC vehicle (and other vehicles of the 70s) that question their engineering choices. Ive heard that GM killed the motorhome production due to the fuel crises but I wouldn't be surprised that safety liability was also connected. There’s a lot about these coaches that scare the hell out of me. I have a shoulder harness set up and I’m not sure it’s better than a lap belt because as Mike said at 50 mph your probably going to die (at best lose your legs) regardless of your seatbelt. But I’d rather not be knocked unconscious or break my face into pieces in an under 50mph bump. As far as rolling goes lap belts may keep you from being strangled (or decapitated as I was told) by a shoulder harness but one better hope the final position of the coach is not upside down especially if the last known rolls destroyed everything from the belt line up. Again the belt thing doesn’t seem to be that big a difference either way to me.
 

Matt Colie

Member
Oct 25, 2019
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Todd,

Many of us have a lot of questions about the incident that killed the Duggers. Nobody has come forward with any specifics that make enough sense to me. More than a few coaches have had engine fires underway and there are none others that cause that level of damage. The Frohms coach was not know to have an oil pressure or impact shut down, but once it got started the local responders had a tough time stopping it.

It was rumored (and I do mean rumored) that the Dugger's coach had a fuel surge tank in front of the engine to supply the fuel injection system, but nobody has confirmed this that I heard. It does sound like something that might have happened but been poorly advised. But a I have not and I have not heard of anybody in the community reporting on the actual investigation, I can offer no more than that.

Matt
 

Wally

New member
Oct 14, 2019
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This has been a really interesting thread and as a guy that spent some time in OE crash testing (two rounds actually), I applaud your interest. There were crash test standards for driver and front seat passengers in the '70s but those were very different than those now.

There was a tragedy this spring. TZE crashed and caught fire. The couple in the front seats could not escape. This might have been because they were both unconscious as a result of the impact. We will never know.

There is one thing you might think about, there have been two coaches rolled. The occupants survived both cases. There are pictures somewhere of the best example because the driver and passenger were still belted in their seats, but the coach was GONE above the belt line. (So, I might advise against anchoring to the B pillar.) Admittedly, TZEs are really hard to roll, but it could happen again.

And, Always marveled how fast flight attendants could pull out that jump seat and get hooked into that five point harness.

Matt
Here is a pic from the photosite of a GMC that rolledNicholls_1062_p12057.jpg
 

6cuda6

Member
Oct 3, 2019
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Ontario, Canada
Guys if you only knew the impact safety requirements, you'd be scared crapless to drive your car......

The one savings grace about these motorhomes is you sit higher than cars and the motor is underneath....so in a collision you dont wear the engine.
 

MikeB

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Oct 26, 2019
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Lower Alabama
These vehicles were made when 55 mph was maximum speed limit. I rarely go over 60 in mine and it amazes me folks comfortably drive 70+ in them.
 

Matt Colie

Member
Oct 25, 2019
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Mike,

The design work was all done by 1972. That was prior to the first "Arab Oil Embargo" and the made up energy crisis. That is why they were shipped with the 3.07. At 70 and with cheap gas, that is a great gear. I know that they were crash tested, as they were under passcar rules.
 

MikeB

New member
Oct 26, 2019
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Lower Alabama
Mike,

The design work was all done by 1972. That was prior to the first "Arab Oil Embargo" and the made up energy crisis. That is why they were shipped with the 3.07. At 70 and with cheap gas, that is a great gear. I know that they were crash tested, as they were under passcar rules.
I thought the consensus was the 3:42 was a better fit and The 3.07 was designed for the Toronado that was half the weight?Im sure folks buying a MH that cost as much as a new house didn’t care much about the gas prices anyway. In any case, I still think the GMCMH on a car suspension is pushing the limits at 70 mph...JMHO.
 
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Mike Perez

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Oct 2, 2019
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I thought the consensus was the 3:41 was a better fit and The 3.07 was designed for the Toronado that was half the weight?Im sure folks buying a MH that cost as much as a new house didn’t care much about the gas prices anyway. In any case, I still think the GMCMH on a car suspension is pushing the limits at 70 mph...JMHO.
My thought on the final drive gearing differs from many people. With that said, I like the 3.07 with the three speed and this is why. My goal is to be able to maintain speed going up hills/mountains. Now we all know that the coach will struggle to maintain speed going uphill in 3rd gear. So now you are gong to have to shift down to gear 2. In my case, I'd like to maintain 65 mph going up the hill. That's the same speed I want to maintain on flat ground. With a 3.07 final drive, 65 mph in gear 3 is 2289 RPM and when you jump down to 2, your RPMs will jump up to 3388. That is still well within my comfort zone. At 70 mph, those numbers would be 2465/3648.

Now let's do the same experiment with 3.42 gears. At 65 mph cruising along in drive, you'd be at 2550. That sounds great until you downshift to 2. Now you are at 3774. At 70 mph, 2746/4064. That's a bit high for my liking.

Now in my case, my engine probably can withstand some higher than normal RPMs because of the way it was built. Also, with extra horsepower, I'd probably be able to stay in drive longer before downshifting. For a relatively stock 455, I'd think the 3.07 gears are fine. It would allow you maintain a higher speed at a reasonable RPM while in 2nd gear. If I didn't have the ability to downshift, then I'd go with 3.42 or even 3.70, but I'm fine with the 3.07 with some added rpm flexibility.
 

Rdenney

New member
Nov 5, 2019
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3
Here is a pic from the photosite of a GMC that rolledView attachment 1793
That was the Nicholls’ coach. A toad misbehaved while underway and the driver swerved and lost control.

Their uninjured survival was miraculous. One can’t say the coach was intended to protect the passengers in a roll, but a shoulder harness tied to a very weak body isn’t a good idea. Maybe to a properly structural roll bar, though that would be impractical. Cars are specifically designed to provide appropriate b-pillar strength.

(The Duggers crashed into a car before running into the house, as I recall—but everything about that situation is just guessing with no way to draw conclusions.)

If a shoulder harness is required, I would use a seat with an integral harness, and add a seat bracket that ties into the existing seat-belt mounts to reinforce the existing mount. Those brackets, small though they are, are designed (and located) to hold both the seat and the passenger.

Rick “risk can be mitigated but never eliminated” Denney
 

MikeB

New member
Oct 26, 2019
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Lower Alabama
That was the Nicholls’ coach. A toad misbehaved while underway and the driver swerved and lost control.

Their uninjured survival was miraculous. One can’t say the coach was intended to protect the passengers in a roll, but a shoulder harness tied to a very weak body isn’t a good idea. Maybe to a properly structural roll bar, though that would be impractical. Cars are specifically designed to provide appropriate b-pillar strength.

(The Duggers crashed into a car before running into the house, as I recall—but everything about that situation is just guessing with no way to draw conclusions.)

If a shoulder harness is required, I would use a seat with an integral harness, and add a seat bracket that ties into the existing seat-belt mounts to reinforce the existing mount. Those brackets, small though they are, are designed (and located) to hold both the seat and the passenger.

Rick “risk can be mitigated but never eliminated” Denney
Rick, I agree with you and would feel better with a seat with an integrated harness.
 

MikeB

New member
Oct 26, 2019
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Lower Alabama
My thought on the final drive gearing differs from many people. With that said, I like the 3.07 with the three speed and this is why. My goal is to be able to maintain speed going up hills/mountains. Now we all know that the coach will struggle to maintain speed going uphill in 3rd gear. So now you are gong to have to shift down to gear 2. In my case, I'd like to maintain 65 mph going up the hill. That's the same speed I want to maintain on flat ground. With a 3.07 final drive, 65 mph in gear 3 is 2289 RPM and when you jump down to 2, your RPMs will jump up to 3388. That is still well within my comfort zone. At 70 mph, those numbers would be 2465/3648.

Now let's do the same experiment with 3.42 gears. At 65 mph cruising along in drive, you'd be at 2550. That sounds great until you downshift to 2. Now you are at 3774. At 70 mph, 2746/4064. That's a bit high for my liking.

Now in my case, my engine probably can withstand some higher than normal RPMs because of the way it was built. Also, with extra horsepower, I'd probably be able to stay in drive longer before downshifting. For a relatively stock 455, I'd think the 3.07 gears are fine. It would allow you maintain a higher speed at a reasonable RPM while in 2nd gear. If I didn't have the ability to downshift, then I'd go with 3.42 or even 3.70, but I'm fine with the 3.07 with some added rpm flexibility.
That’s an interesting take on the 3:07 especially with a built motor (or diesel). I have a 3:70 with a built motor so I have no knowledge of the difference a higher gear would provide. Here is some interesting read that points out some other benefits of the 3:42. https://www.thegmcmotorhomepeople.com/news/gmc_newsletter.pdf
 

tmsnyder

Member
Oct 7, 2019
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Not to take this thread further off topic, but 3.07 FD ratio with Toronado sized tires is different than 3.07 FD ratio with GMC motorhome sized tires. They are different diameter tires by almost 7%. To get the same engine rpm in the GMC as in the Toronado, the FD would have to be about 3.27 instead of 3.07. Imo they probably did intend to change the gearing, or at least they should have.
 

Mike Perez

Administrator
Staff member
Oct 2, 2019
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That was the Nicholls’ coach. A toad misbehaved while underway and the driver swerved and lost control.

Their uninjured survival was miraculous. One can’t say the coach was intended to protect the passengers in a roll, but a shoulder harness tied to a very weak body isn’t a good idea. Maybe to a properly structural roll bar, though that would be impractical. Cars are specifically designed to provide appropriate b-pillar strength.

(The Duggers crashed into a car before running into the house, as I recall—but everything about that situation is just guessing with no way to draw conclusions.)

If a shoulder harness is required, I would use a seat with an integral harness, and add a seat bracket that ties into the existing seat-belt mounts to reinforce the existing mount. Those brackets, small though they are, are designed (and located) to
Not to take this thread further off topic, but 3.07 FD ratio with Toronado sized tires is different than 3.07 FD ratio with GMC motorhome sized tires. They are different diameter tires by almost 7%. To get the same engine rpm in the GMC as in the Toronado, the FD would have to be about 3.27 instead of 3.07. Imo they probably did intend to change the gearing, or at least they should have.
True, but my RPM numbers in my example above were calculated with GMC tire diameter of 29.29”.
 

tmsnyder

Member
Oct 7, 2019
99
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Hi Mike, I didn't mean it as a response to your post, just in general, that the 3.07 in the original application with the smaller tires may have been fine for a car, but in the MH it probably isn't the best ratio. To keep the MH rpms the same, the GMC engineers would have had to put ~3.27 fd in it b/c of the larger tires and who knows if they even make one, 3.42 would have been pretty close though.

One added benefit though of the 3.07, it makes 2nd gear 'Super'! Anyone else read the owners manual and notice that they encourage traveling in 'Super' gear all the way up to ~70mph?!? So basically they were selling a mh with a 2 speed (a la powerglide) + OD transmission LOL
 

Rdenney

New member
Nov 5, 2019
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My 3.21 seems like a good choice for a light coach that doesn’t tow. Not quick off the line, of course. I can still use Super to climb over the steepest hills going over the Eastern Continental Divide on I-68, which seems to be on my route to most places west. Never get below 45 on those hills, passing trucks like crazy. And the 3.21 is reportedly a bullet-proof planetary design.

But I’d still be using the 3.07 had it not been worn out. A worn final drive has too much thrust play on the input shaft, which is not good for the transmission.

Rick “flooring it on Sideling Hill” Denney
 
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MikeB

New member
Oct 26, 2019
21
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Lower Alabama
External. I called that manufacturer. See my original post with the "trucker" seat setup. You take the tether belts and attach them from the original seat belt anchor points and then they are bolted to the seat base. It may work fine, but would be ugly.
Mike
Any progress on the seats with integrated belts and swivel base?