W116 300SD Seat Compatability

[Putty]

Does anyone know if any other MB Seats could be put in a W116 with slight modification? W116 seats are hard to come by BUT, I see a lot of W126 and W123 seats in my local salvage yards. I wouldn't be afraid to relocate some mounting holes...maybe even do some custom electrical work if I ended up with power seats. I just was curious if anyone has attempted this and if they have had any success. Perhaps the MB gurus know general dimensions of the seats and if they would even fit in the space.

Your Thoughts?

[Alec300SD]

I haven't installed complete W126 front seats in 'Desert Rose'.

However, one of the first upgrades I did for my 78 W116 300SD was to replace the front seat cushions (spring boxes, padding, and skins) with those from a late W126.
The late W126 spring boxes have extra support compared to the earlier designs.
The same will be done on my 79 W116 300SD 'Stormcloud'...the black leather W126 seat cushions pulled on Monday just need to be freed from their motorized bases.

DIY – Pictorial - W126 Front seat cushions in a W116

If you decide to go this route, use the PS seat cushion for the DS, as it will have less wear in most cases.

[Putty]

That's a really cool write up! Why did you opt to keep the original backrests though? Did they not fit? Didn't like the look of the W126? I'm curious because I would be fine to swap the whole thing. Do you think the boltholes for the tracks will fit...or at least be close?

[Alec300SD]

The original W116 seatbacks are still okay on 'Desert Rose' other then wear on the left DS bolster that exposed the green plastic-coated horsehair padding.
I do have a darker brown front seat MB-Tex skin that has yet to be installed on the driver's seat.

The W126 seatbacks are are not manually operated, and I didn't want to add any more electrical complexity.

I did try to convert one W126 seatback to manual, by removing the seatback adjuster from a W116 and transplanting it to a W126 seatback.
I used a cutoff grinder to remove the rivets that hold the adjusters to the hinges.

The W126 seat hinges have the same dimensions as the W116 seat hinges, but on my off-the-car mockup the W126 seatback with the W116 manual adjuster modification resulted in a maximum forward seatbank angle that was much less than what I find to be comfortable.

I'm not sure if the motorized W126 seat frame rails will directly mount into a W116 without some sort of modification.

I'll test it out, and report what I find, when I remove the front seats from 'Stormclould' this weekend

[Putty]

I bought some seats from a W123 today with the MB Tex and they are in excellent shape at my local pick your part. The tracks are the same width but the length is 2 inches longer than the original. I'm debating whether I should swap the tracks or just drill new mounting holes and hide them with the carpeting.

[mabbonizio]

I installed both front and rear w123 seats in my w116.

Fronts:

I swapped the seat tracks. Its a bit of a ***** but once you do the first one the second goes much quicker.

Rears: ( had to get a little creative here)

I purchased one complete w123 sedan rear seat + an additional w123 rear bench at the u pull it.

Removed all the gross old padding from the w116 rear seat frame and cleaned off the frame.

Removed both w123 rear bench covers and foam pads. Measured and cut one foam pad in half in the center, then cut a few inch chunk from the center of the other pad and taped it in the middle of the bench pad I cut in half.

Put new w123 foam pad on the w116 seat frame and GENTLY stretched the MB tex cover over it. - Installed right in the car.

For the rear back rest I simply installed the w123 back rest in w116. There was a approx 1" gap on either side of the back rest between back rest and car body. I simply used long self tapping screws in place of the shorter stock screws that screw the brackets on the bottoms of each side into the body of the car. As I tighten the screws the seat back was stretched enough to fit tight.

Its not perfect but considering how bad the padding and cloth seats where before I'd say its great. Most people think its stock.

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[mabbonizio]

I installed both front and rear w123 seats in my w116.

Fronts:

I swapped the seat tracks. Its a bit of a ***** but once you do the first one the second goes much quicker.

Rears: ( had to get a little creative here)

I purchased one complete w123 sedan rear seat + an additional w123 rear bench at the u pull it.

Removed all the gross old padding from the w116 rear seat frame and cleaned off the frame.

Removed both w123 rear bench covers and foam pads. Measured and cut one foam pad in half in the center, then cut a few inch chunk from the center of the other pad and taped it in the middle of the bench pad I cut in half.

Put new w123 foam pad on the w116 seat frame and GENTLY stretched the MB tex cover over it. - Installed right in the car.

For the rear back rest I simply installed the w123 back rest in w116. There was a approx 1" gap on either side of the back rest between back rest and car body. I simply used long self tapping screws in place of the shorter stock screws that screw the brackets on the bottoms of each side into the body of the car. As I tighten the screws the seat back was stretched enough to fit tight.

Its not perfect but considering how bad the padding and cloth seats where before I'd say its great. Most people think its stock.

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[Putty]

Thank You! That is really reassuring especially given the condition of these seats...ill post pics. I was thinking id need to modify them more but I think i can clean up the old tracks and reinstall. Unfortunately, the W123 at the pickpart was a wagon, so the rear seats won't work. I guess the hunt is still on for a rear seat in Navy, which I'm finding particularly hard to find (90 percent of all interior colors I'm seeing are beige). After pulling up the carpet for steam cleaning, I realized I have a leaking window seal somewhere (minor rust)...so, guess I'll be installing new seals.

[guyonabuffalo]

I did the opposite of what you are attempting. W116 seat installed in my W123.

as mabbonizio stated, its a pain in the D#$K !!

There are numerous screws and bolts that need to be removed to change the tracks. Remember to take a lot of photos with the small stopper pieces highlighted. I lost/forgot a metal piece that normally goes near the front of the track assembly. Now I cant get the seat as far back as the passenger side (I am short so its not a big deal but anyone taller than me would have trouble). Since that piece is permanently lost, I will wait till I find a nice front Drivers side track again to tackle this - correctly.

Good luck with your swap. Looking forward to your pictures.

[Putty]

DEAR LORD! You weren't kidding when you said it would be a pain in the D***! The rear bolts on the W116 seats aren't threaded...they have a lower square lock nut that is rusted and horribly inaccessible!!! I ended up having to just rock the seat back and forth until it broke the bracket. Luckily, it was rusted anyway, but now, I'll have to make new brackets and tack weld them in there. I guess its not a big deal...I have to repair a few little rust spots anyway.

As for the seats themselves...the arrangement of these sliding rails is asinine! My old 79 Benz had some corrosion on the railings and I had to spray it down with nut buster just to get the rails to move somewhat easily but I still had to bash the heck outta them with a hammer to get the holes to line up for the screws! Luckily, the W123 seats upper sliding rail was fine to stay on there but the angle bracket, locking claws, and trim all had to be replaced.

The worst thing was getting everything almost finished just to find that the W123 handle that LOOKED almost the same as the W116, wouldn't work...and you had to disassemble half the seat again.

HOWEVER...let it be known, it IS possible to swap W123 seat hardware with W116! I have one of the seats finished and will post pics when I figure out why this website keeps failing to upload my pics.

[Clemson88]

Open the photo with your Windows Paint program. Click on the 'resize,' icon and type in '25,' where it says 100. Save the photo then try the upload again.

This website, as do most forums, limit the size of the uploads.

[Putty]

Alright guys and gals! Here is my write up on how to swap a W123 seat into a W116. If you are like me, you are finding it hard to find seats for your W116 especially in navy. I couldn't afford $900 for JUST the seat covers so I decided to hit the internet and found a nice set of W123 bucket seats in a pick your part. W123 seats seem to be everywhere and with a little reassurance from my buds at peach parts, I decided to tackle this project and it is indeed possible to do!

This was what I started with...a irreparable W116 seat from 1979 complete with cracks and broken springs.


On the left is the foam padding that was jammed into the springs and on the right is my W123 donor seat. I found it easier to have the seats in this position and side by side...it made it easier for keeping track of parts and progress.


These are the tools you will need. First, three things not pictured are a #2PH socket, a 10mm socket and a wire wheel (if you had corrosion on your tracks like I had and the chassis bolt was still attached). You will need a pry bar, can of nut buster (or any decent lubricant), a #3 or #2 phillips screwdriver, and a rubber mallet. You may want to also have a drill with 3/16 drillbit.


First, lets start with disassembly of the W116 seat The W116 had a STUPID design of making the lower threaded nut horribly hard to get to and if you had the slightest bit of rust, it would strip out and you would have to literally break the bracket out of the car to get the seat out...so, lets get rid of that old 10mm chassis bolt if you still have it attached.


continued on next post...

[Putty]

At this point, it is best to look at this project in three distinct sections:

1. The lower slider



2. The support bracket



3. The Upper slider



You have to disassemble one section at a time...you cannot take the entire assembly off at once.

First, lets start with removing the three screws that make up the lower slider. One on each end and one in the middle. Note that on the lower slider there are oversized holes drilled in it...this is to get a screwdriver in the slot to remove the third hidden screw. You will find that if your sliders are not very lubed up and don't move very easily, you will need the rubber mallet...you will be sliding the sliders back and forth a number of times throughout this project.



continued next post...

[Putty]

The sliders on the W116 had two spring loaded adjusters...one on the left side for the upper slider and one underneath the seat for the lower. They also had a large return spring that, if you haven't done it already, remove it.



Make a note of this as there is a subtle difference in the W123. Because they are spring loaded and have a tendency to lock, I found it was easier to use a pry bar to hold the locking teeth out of the way instead of using the handles.



Once the lower slider has been removed, the lower spring loaded catch can be removed...SAVE THIS, you will need it. Try not to crack the plastic trim as you remove it...gently pry it away from the bracket at the rear of the seat and try not to break the little locking tab. The plastic piece can remain dangling from the catch, if you haven't broken it, it can go right back into the new seat. Don't forget the little rubber grommet that was holding the other end of the catch...you MIGHT need it later.



The other side is disassembled the same way.

Another thing to note is that one of the spring loaded catches controls the lower slider and the other side catches the other (these are on different sides depending on the drivers side or passengers side).

This is what the middle angled support bracket will look like with the whole lower slider assembly gone.



continues next post...

[Putty]

We are almost done with disassembly! Now to remove the middle angled support bracket...which is a breeze...4 total screws, 2 of them facing you and the other 2 is the one you will need the #2 phillips socket to get at.





The locking rail will come off with the bracket...hold onto this.

Congrats, you should just be left with the upper sliders!
One last thing that needs to be done...remove the UPPER slider ONLY ON THE SIDE THAT I HOLDING THE REMAINING SPRING LOADED LOCKING ARM. Nothing BAD happens if you completely disassemble everything, it is just a waste of time.



There are 3 screws on this rail but you only need to remove the rear one and the hidden one...once you do this, you can pull up on the whole rail and remove the lock arm from under it.



Once you do that, youre finished with disassembly!!