Rear End Coil Spring Perch/Mount - Different Designs

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Post by g3chevy on Tue Apr 09, 2019 10:53 pm

Today I stumbled across something I've never seen before when doing a rear end swap. When looking at the spring perch on the rear end I just removed from my 77 El Camino, it appeared to be a different shape and location from the one I'm installing on the vehicle. The replacement rear end came from a 74 El Camino. I've always assumed these housings where identical. Well that's not the case with this project. Here's a video showing both rear ends.

https://youtu.be/uAb2IXqIUfo

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Post by ant7377 on Wed Apr 10, 2019 5:56 am

The later one seems more robust. Maybe there was a problem with failures. Especially on an Elcamino with a load in it.
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Post by Joe73 on Wed Apr 10, 2019 10:12 am

Any chance one is a chevy rear and the other is BOP ? Just a thought.
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Post by g3chevy on Wed Apr 10, 2019 10:29 am

No, both are c-clip rear ends but that's and interesting question. I have a BOP rear end that uses the axle retainers on my 75 454 El Camino so I'll get some pics of it and see what it looks like.
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Post by 73ss on Wed Apr 10, 2019 7:13 pm

I haven't seen that before. When I did my rear I noticed that one of the perches was a degree or 2 off from the other side. I went ahead and installed it and the spring is sitting fine and the ride height is the same side to side. If it was off I was going to cut it off and re-weld but it's fine.

Of course I did not notice it until after I blasted, clean, Prime & painted the rear. It's a BOP rear, the perch looks like your first pic.
I would think the perch in your second pic would have started to fold over from the weight.
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Post by g3chevy on Wed Apr 10, 2019 11:34 pm

Looks like my 75 SS 454 El Camino with BOP rear end have the square spring perches like the 74 rear end. I have a 76 El Camino parts car that I'll check this weekend to see how its setup. I'm thinking the later rear ends have the round spring perches since GM tried to save weight and reduce production costs in the mid to late 70's.

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Post by g3chevy on Wed Apr 17, 2019 1:49 pm

Thought that all the rear ends with 11" drum brakes might have the round spring perches. But that is not the case. My 76 SS El Camino parts car has the square spring perch. Does anyone have a 77 El Camino or Malibu they can check?

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Post by Hawk03 on Wed Apr 17, 2019 8:17 pm

My '77 Malibu has the round perches

Hawk03 wrote:
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Post by g3chevy on Wed Apr 17, 2019 8:55 pm

Interesting... Might be a 77 only thing??? Hawk03, did you get your steering column installed?
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Post by 77camino on Thu Apr 18, 2019 8:34 am

My 77 El Camino has the round perches alsoRear End Coil Spring Perch/Mount - Different Designs 9fb75010
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Post by g3chevy on Thu Apr 18, 2019 10:40 am

Cool. Looks like this is exclusive to most or all 77 A-Body vehicles. I'm wondering if they did this for better suspension geometry? Or this was some cost cutting change in production?
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Post by Joe73 on Thu Apr 18, 2019 1:43 pm

I highly doubt a different style spring perch on the axle, that still lines up with the same pocket on the frame up top, would have any change to geometry. Geometry would be greatly effected with repositioning the upper and/or lower control arms or angles.
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Post by bigredlaguna on Thu Apr 18, 2019 3:34 pm

g3chevy wrote:Cool. Looks like this is exclusive to most or all 77 A-Body vehicles. I'm wondering if they did this for better suspension geometry? Or this was some cost cutting change in production?

Cost cutting 100%. This design change doesn't affect performance, and the miniscule amount of weight reduction per car translates into big savings on raw material cost.
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Post by g3chevy on Thu Apr 18, 2019 5:16 pm

Cost cutting makes perfect sense. But I'm still wondering why they would move the mount 1/2" further out from center than the original design? Could be so the brake line tucked under it nicely like the earlier version but using less material? Who knows. I've seen many different variations in designs from hoods, hood latch brackets, swivel bucket seat bases, fenders etc. so I guess this is just another one of those...
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Post by Hawk03 on Fri Apr 19, 2019 5:37 pm

g3chevy wrote:Interesting... Might be a 77 only thing??? Hawk03, did you get your steering column installed?

Not yet, the weather turn cold quickly last year before I could paint the shaft and touch the column from where I scratched it trying to install it before. I bought a dash pad too and wanted to install everything (shaft, column and dash) at once but need to paint the dash pad. Its finally warming here so I can start painting everything.
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Post by g3chevy on Fri Apr 19, 2019 9:16 pm

Winter just keeps lingering on this year. I've had the same issue with painting, but mine is because its been too wet or humid. We finally got a nice weather weekend so I'm hoping to get some stuff done as well. Keep me posted on the column install. Just want to make sure it works for your setup.
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Post by Hs1973 on Mon Apr 22, 2019 2:34 am

There is sometimes weird things you find on 2 identical cars. Small brackets thats changed or different designs on latches. 
When i restored my chevelle 75 i actually bought 73 fenders thinking they where the same, however even if they look the same they fit like crap to the light buckets and the hood. Ive been having a tough time when i put the fenders on. 

They lined up Nice to the doors since they Came from the same car ( rustfree California junkyard elcamino) so there is defenently difference in parts from year to year or plant to plant.
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Post by Iggy on Mon Apr 22, 2019 11:25 am

I was given a 1975 Olds Cutlass rear axle and was told it has a posi - it does not, but I saved it from being scrapped! My plans are to rebuild it and gear it for my 1975 Laguna as I like the idea of eliminating the C-Clips. This thread made me take a closer look and the Olds axle has the heavier square spring mounts - I am like this axle more each day! I have the backing plates from a 1977 Monte Carlo with 11" drums that I will be putting on this axle so it will be a true Frankenstein axle when done!
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