Eliminate rear bumper rubber filler on a 74 Duster

-
DusterDaddy

DusterDaddy

sledgehammer mechanic
FABO Gold Member
Joined
Apr 21, 2011
Messages
2,568
Reaction score
1,791
Location
Holmdel, NJ
I have seen some talk about moving the rear bumper in towards the body on a 74 to eliminate the need for the grey rubber strip.
I drilled out the impact absorbers straight through, and was surprised that only a few drops of oil came out of each one. I cant push them in by hand, but I can now rotate them which was not possible prior to drilling the holes.
My plan is to use a large C-clamp from the outer plate to the rear angle where it connects to the frame to compress the absorbers.
I was thinking of driving a sheetmetal screw through the hole into the inner cylinder and test fitment of the bumper, then weld the inner sleeve to the casing when I know they are in the right place.
Good plan? Anyone have a better one?
 

Attachments

  • rear filler.jpg
    16.7 KB · Views: 1,641
  • absorber (2).jpg
    35.7 KB · Views: 894
  • absorber (1).jpg
    55.2 KB · Views: 907
No, I say you get an A.
My Duster is getting 2 new quarters so maybe the side gap can be improved in the process.
Do you remember if the nut in the frame rail is welded to the side of the rail?
If not how did you grab it to remove the back bolt holding the shock?
Thank you very much!
 
Just hang a railroad tie off the *** end.....you will be good to go...
 
Dusters and sports see sisters with the same *** end.
You can swap for the older bumper as well.
 
Does anyone know what the head size of the large bolt on the front side of the back bumper shock is on 74 Duster and can you tell me if the nut is welded in place inside the frame rail?

I am eliminating them and it's larger than 7/8" ( I had a small set of sae 1/2" drive sockets which have vanished)

Thanks for your help!
 

Attachments

  • shock.jpg
    35.8 KB · Views: 646
Here: bumper bracket

IRC the bolt is 1 1/8" or 1 1/16" socket. Nut is welded to a reinforcement plate inside the frame rail.

I ultimately replaced my '74 rear bumper with a '72 because the ends of the '74 stick out past the body lines too much for my liking.
 
rapom65 said:
Here: bumper bracket

IRC the bolt is 1 1/8" or 1 1/16" socket. Nut is welded to a reinforcement plate inside the frame rail.

I ultimately replaced my '74 rear bumper with a '72 because the ends of the '74 stick out past the body lines too much for my liking.
Click to expand...

Yup, I feel the same way...It's pathetic that I can't locate my 1/2" drive set.
 
omahamoparguy said:
what is exactly inside the energy absorbing bumper?
Click to expand...
There is this hellatious steel inner bumper behind the exterior chrome one. As far as the shocks go, I'm not sure but there isn't any fluid to speak of. May some kind of crumple design on the inner sleeve of the shock???
 
^No, I don't think that's it. I only say that because when you get rear ended and the compress, they will most of the time either pop back out on their own, or with a little persuasion they will extend again. I was rear ended in my Dart, and the passenger side came back out on its own, the drivers side we pulled back out.
 
Very stout spring, just enough oil to keep things wet, and a threaded center rod to keep it from coming apart. A tube within a tube with a spring inside. It will compress with small hits and rebound back out under spring tension. I chopped this one completely in two with a chop saw but all you have to do to take one apart is cut the inner tube shell in half.
 

Attachments

  • IMG_1444.jpg
    20 KB · Views: 648
rapom65 said:
Very stout spring, just enough oil to keep things wet, and a threaded center rod to keep it from coming apart. I chopped this one completely in two with a chop saw but all you have to do to take one apart is cut the inner tube shell in half.
Click to expand...

It's a shock autopsy! Now we know.
 
Adding the earlier bumper is the better way to go. And I'm not just saying that because that's what I did. :D

The '74 bumper is massive. It doesn't weigh twice what the early bumpers weighed, it probably weighs 5x as much. The bigger issue is that even if you re-do the brackets and bring the bumper closer to the car, the bumper is still wider than the back end of the car is. It's not as obvious with the rubber filler in there, but if the shock mount bumper is probably a couple inches wider than the quarters are.

As far as the side gap on the quarter with the earlier bumper, my initial how-to was a little misleading (thanks for all the love guys! :cheers: ). The "indent" for the bumper is the same on both the early and late quarters. The difference is that the earlier quarters came together with the tail panel there with a flange, where the later ones just have a flat overlap. So the earlier quarters have a built in filler panel. It's really not that noticeable unless you really look for it. Also, I didn't realize there's a little rubber spacer that's supposed to sit on top of the bumper between the tail panel and the bumper. My bumper is set to be almost flush with the bottom of the tail panel.

These pictures explain it better. Just find a used early bumper and brackets. It can be pretty close to a bolt on operation depending on how you do it. And you'll probably knock almost 100lbs of the car.

Here's mine - '74 Duster with a 71/72 bumper

IMG_5239_zps989e8713.jpg


And the real deal, a couple of '71 Demons
 

Attachments

  • IMG_5387.jpg
    45.4 KB · Views: 636
  • IMG_5386.jpg
    50.1 KB · Views: 645
  • IMG_5402.jpg
    43.6 KB · Views: 611
That looks a billion times better than the 73-76 with the rubber filler
 
I agree that it looks heaps better, and lighter weight is stellar!

My only concern, since I have been rear ended hard, with lots of damage to the dart, is how well will this take an impact? I know how the body crumpled on mine, how do the earlier (pre-shock absorber) cars fare in such cases? Anymore, I consider safety a lot lol.
 
Brandon Weaver said:
I agree that it looks heaps better, and lighter weight is stellar!

My only concern, since I have been rear ended hard, with lots of damage to the dart, is how well will this take an impact? I know how the body crumpled on mine, how do the earlier (pre-shock absorber) cars fare in such cases? Anymore, I consider safety a lot lol.
Click to expand...

The larger bumpers were designed in response to a new federal 5mph impact standard that took effect in 1974/75. In low speed impacts the heavy bumper and shock absorbers will fare better than the earlier bumpers, that's what they were designed to do.

But in a higher speed impact its not going to make much difference. Both early and late bumpers are still attached to the same frame rails and rear crossmember. Once the springs in the shock absorbers bottom out, everything is getting pushed into the car. With an impact under 10mph or so the amount of energy absorbed by the shock mounts is enough to make a difference. With a 30mph impact, the shock mounts are going to bottom out almost instantly and the frame rails are going to bend anyway.

I parted out a '74 Swinger that had been rear-ended at around 35mph. The bumper was a little tweaked, but it actually looked pretty good. The shock mounts were even able to unload again. Those later bumpers are bombproof. But one of the shock mounts pushed right through the rear crossmember, the entire right quarter panel buckled, and so did the right rear frame rail. Pulled a good 8 to 9" section of frame rail right off the floor pan at the spot welds. :violent1: Pushed the whole back end of the car over about 2", which was visible because the trunk lid popped open in the accident and wasn't damaged. But when you tried to close the trunk lid it was about 2" to the left from actual the trunk opening. ;)

The later shock mounted bumpers were just a band aid to get past a new standard. The actual structure of the cars wasn't redesigned, and that's where your actual safety comes from. Unless you back into a lot of parked cars or parking lot bollards, the later bumpers aren't worth their weight or appearance. The earlier bumpers won't take as much abuse themselves, but they're still bolted to the same car.
 
72bluNblu said:
The later shock mounted bumpers were just a band aid to get past a new standard. The actual structure of the cars wasn't redesigned.....they're still bolted to the same car.
Click to expand...

Once again agree completely with 72's points above. They did nothing more than bolt on an extremely heavy bumper core, behind a standard chrome bumper, mounted on two springs to take small bumps without damage. Once the give of the springs is taken up the exact same rear structure as earlier cars takes on the impact. My '74 had the same treatment up front (heavy core/bumper cover) but mounted on standard brackets not shocks. There must have been a different standard for front impacts that year as latter cars had shocks front and back.
 
The 1973 models used the same size rear bumper as the 70-72 but often had the added bumper guards bolted to them.

For my 1974 "FrankenDuster", I welded sheet metal plates across the huge holes in the rear frame/crossmember that were originally there to allow the 5 mph shock absorber to pass through. I then simply used an AMD bumper for a 70 Duster and 70-73 brackets. The front also had the 5 mph bumper. I switched to a 70-72 hood, grille and bumper up front so to mount the traditional bumper brackets, I made my own sheet metal plates with captive nuts welded to them and slid them inside the frame rails. There seems to still be more 73-76 Dusters and Dart Sports around compared to the more desireable 70-72 models . I'm glad that it is so easy to "back date" the cheaper & more abundant cars.
 
I wouldn't be so quick to say that a hacked up 70-72 clone is more desirable than a nicely done '73 up car...
Not sure I'd hange my bumper supports off sheet metal either...Just sayin.
 
You must log in or register to reply here.
-

Back
Top