Cargo to Passenger Van Bench Seat installation questions & recommendations

[CaliforniaStars]

Hello Sprinter community I have a few questions and would like some suggestions please.

2005 T1N sprinter -
Im installing a stock bench 3 seat. There are 2 pre cut holes that lines up exactly with the brackets. My first question is I want clarification on the direction of the brackets. Down is the facing front direction in this photo. With the long and short cross bar facing forward.

Down is the facing front direction in this photo. With the long and short cross bar facing forward.

Here is the bottoms. The right is steeper, and left side longer and shallower. Which faces forward towards driver?

The floor has 2 starter holes. So I should be able to align it just right. But no screw bolts.

My second question is does anybody suggest welding a bolt in place? Or how many think it’s fine to drill through the box frame and secure with strong bolt and lock nut with steel support pad.

I have no welding skill, and with the quarantine I’m not sure how to get that welded. My only concern is safety of eventual long term use.Suggestions?


I pulled up the old flooring down to the metal, prepped for rust and fiberglassed holes and spray painted.

It has a black mercedes mat I’ll reuse. The wood is good and already cut to size.

does anybody suggest filling between the ribs with reflectix strips or if that even worth it?

Questions recap,

Please clarify the direction of the seat brackets?

Bolt through frame or weld in place screws?

Insulate between ribs or waist of time.

Any help of advice or point me in the right direction is helpful.

Getting her ready for summer


2005 Dodge Sprinter
Get out there and do it

 

[Patrick of M]

The best way to work out your brackets is to put them on your bench seat to see which way they install, then load the assembly into the van to get the floor bracket position correct.
All the 3 seat benches i have installed had three brackets.
I used a combination of long bolt through the box beam with a backing plate/ bolt through the floor with a backing plate and big riv nuts (14 mm i think, I had to order them online, no one had them in town). Use the best grade fasteners. The rivnuts are required on the left side as the fuel tank is in the way... you could drop the tank and put backing plates in, but I chose rivnuts.
Extra notes: my van had the factory plywood flooring in it which helps support the edges of the brackets but technically shouldn't be required.
Second note ncv3 seats don't install properly in a t1n but it is nonetheless possible with some fiddling to get an NCV3 seat and it's brackets mounted in a t1n.

 

[Nautamaran]

The sloped ends all face forward (long+short facing rear of van).

You may wish to review this thread:
https://sprinter-source.com/forum/showthread.php?t=8481

There is a shorter third bracket that secures the middle leg of these 3-across benches. The three brackets fit into the stamped depressions in the floor pan. (The middle bracket depression is above the drive shaft, visible if you crawl under the van)
See here: https://sprinter-source.com/forum/showpost.php?p=703687&postcount=19

Be aware that the floor pan metal is relatively thin, and in cargo vans was not reinforced for the loads generated by the bench and its occupants in the event of a crash. The pullout force on the rear bolts and the “diving” loads across the front should not be underestimated, and result from the momentum of the bench and the seat belt forces. Passenger vans have added framing and supports to distribute these loads to the van’s structure. In my opinion simply tacking bolts into the floor pan is inadequate, and drilling down through the bottom of the frame weakens the beam (though many do so, it violates best practice, which is to drill only through the sidewalls of the frame.

I chose to cut the floor open and weld thick plates onto the upper sidewalls of the frame, with stacked nuts providing full thread engagement to the factory anchor bolts (pictured, along with the inadequate nuts poorly tacked in place by a previous owner...)

Another approach might be to drill larger holes into the sides of the frame and pass stout bars across the frame‘s neutral axis to anchor bench bolts. These bars would be drilled and tapped to accept the bench anchor bolts inserted down from above. This would have the advantage of leaving the upper and lower faces of the frame undisturbed.

Honest Disclaimer: I am NOT an engineer. The engineers I know wouldn’t touch this discussion with a ten foot pole. Adding seats to an automobile for use on public roads is a regulated activity in many jurisdictions. Proceed with due care, and strongly consider hiring a competent installer, which may shift liability in the event of injury (but I’m not a lawyer either).

-dave

 

[CaliforniaStars]

Thank you gentlemen.

I’m inclined to just bolt through the box frame with backing plate and good hardware. With no welding equipment I don’t think I have any other option. Unless anyone can convince me otherwise.

Thank for all the suggestions and replies. Very helpful.


2005 Dodge Sprinter
Get out there and do it

 

[jrod5150]

Thank you gentlemen.

I’m inclined to just bolt through the box frame with backing plate and good hardware. With no welding equipment I don’t think I have any other option. Unless anyone can convince me otherwise.

Thank for all the suggestions and replies. Very helpful.


2005 Dodge Sprinter
Get out there and do it

I don’t think it’s possible to not drill through the frame rail as the dips line up with the frame rail. I was hesitant to drill through mine as well. Really stupid of Mercedes to not have the threaded holes like the passenger vans.

 

[trc.rhubarb]

I used steel plates inside the frame rails. I went pretty long just to spread the load.
Dropping the gas tank is a non-issue if you have a tranny jack or a motorcycle/quad lift handy. I did mine about half full.

Sadly, i had a bit of a brain fart due to a TBI and my first 2 holes i cut with a grinder and will need to repair eventually.
A hole saw was very simple.
My only other thing I'd like to do is to tackweld the nuts in place so that i can remove the plates for access under the floor. This will be key for when i patch the frame rails back up.

 

[jrod5150]

I used steel plates inside the frame rails. I went pretty long just to spread the load.
Dropping the gas tank is a non-issue if you have a tranny jack or a motorcycle/quad lift handy. I did mine about half full.

Sadly, i had a bit of a brain fart due to a TBI and my first 2 holes i cut with a grinder and will need to repair eventually.
A hole saw was very simple.
My only other thing I'd like to do is to tackweld the nuts in place so that i can remove the plates for access under the floor. This will be key for when i patch the frame rails back up.

Man that seems like alot of extra work for a unibody frame vehicle. I think your holes will never be an issue unless your hauling around insane amounts of weight. Million mile sprinter and portland sorinter connection both have alot of experience with all of this

I used a long drillbit as a starter then I increased the hole size with a unibit. I always run the fuel down as low as possible when dropping a fuel tank and use a regular floor jack.

 

[ECU]

I tried nutserts that spun. I had a shop weld in nuts from the top. didn't need to drop the tank. Cost me $30 and saved lots of time.

 

[trc.rhubarb]

I tried nutserts that spun. I had a shop weld in nuts from the top. didn't need to drop the tank. Cost me $30 and saved lots of time.

How did you get nuts in through the top to be welded in place and how did you provide pull out reinforcement? The floor is very thin and i wasn't comfortable putting my daughter in a seat held in place without spreading the load with something. No way i could have done that from the top without cutting out the floor in sections and welding it back in.

 

[Nautamaran]

I tried nutserts that spun. I had a shop weld in nuts from the top. didn't need to drop the tank. Cost me $30 and saved lots of time.

This sounds a lot like what I chose to cut out of my van (see photo above).
If your shop just welded around the circumference of the nut I wouldn’t consider it crash worthy?
I hit one of mine with a 4 lb hammer and it broke the welds... maybe 10 foot pounds of energy? Scary to think of my three kids riding the bench through the glass during an accident.

-dave

 

[CaliforniaStars]

Yeah I agree a weld around the top ir I’m frente of the bolt does not seem that strong. Mercedes must have reinforced them somehow to be crash worhty. The 3 person bench is heavy.

So I’m back to drilling through the frame and reinforcing with a steel plate. No way that is coming out or breaking.


2005 Dodge Sprinter
Get out there and do it

 

[full metal racket]

Yeah I agree a weld around the top ir I’m frente of the bolt does not seem that strong. Mercedes must have reinforced them somehow to be crash worhty. The 3 person bench is heavy.

So I’m back to drilling through the frame and reinforcing with a steel plate. No way that is coming out or breaking.


2005 Dodge Sprinter
Get out there and do it

Are you bolting through the whole box frame with a really long bolt? Would like to see pics if you have any as I want to install brackets and would like to avoid welding.

 

[CaliforniaStars]

Yes exactly. I will post some pictures shortly

 

[220629]

Not that anyone asked...

It is highly unlikely that even the stresses on the "long bolt" during a crash will be high enough to compromise the Unibody "frame rail" integrity. That assumes sufficiently large (bearing surface area) plates.

As I have put forth in other posts.
[For the most part, in the USA...] The bottom line is that any seat aftermarket design or DIY attachments never fail. If the seats stay in place during/after a crash everything is ok. If not, any mediocre lawyer will have a field day in court.

FWIW.
vic

 

[areeevan]

Yes exactly. I will post some pictures shortly

About to start my bench instal. Do you have those photos for reference?
For consistency, plan is to bolt through the frame rail on both sides of the van, with reinforced plates on both sides (under the bolt head, and also under the nut).
Will see how that works with the gas tank alignment, may need to add some 1inch or so spacers upon reinstall.