Shock Mounts for Older Mopars- Tech

WooHoo- My first Tech post, and this is really useful:

If you have a mid-30's to early 50's Mopar you've got an a very nice- almost modern- IFS already on your car, but it probably doesn't feel like it. The reason is that the Mopar engineers- clever though they were- foolishly ran the shock between the upper and lower (unequal length) control arms. The because of this the shock didn't really compress/extend much, and you had the wallowing boat-like ride that we all know and love.

The fix is pretty simple: Make an upper shock mount and attach it to the frame instead of the upper control arm. There are at least a couple of people making kits for this, and I bought one the first time I did it, but after that I just made my own, and if I can anybody can.

I've done this on a 50 Plymouth and a 38 Chrysler. The details varied slightly between the two, and I'll be mixing pics of the two in this post as necessary, so Lemme know if this confuses you.

To get started you'll need to cut some metal: For the upper shock mounts you'll need 3/8" material (ignore that I said "Plate" on the diagram- it just needs to be flat). I don't have a plasma cutter, so I went to a local guy who does water jet cutting. Cost me about $25 for everything. Here's what you're making:


You'll need 2 pieces. You'll also need:
>> 2 pieces of 1/4" stock cut 1.5" x 3" for lower tabs.
>> 2 pieces of 1/4" stock cut 4" x 4" for upper backing plates.
Here is what the tabs will be for after you drill a hole in them:


Now a little welding: Take the upper shock mounts and weld them on edge to the center of the 4x4" backing plates. They'll look kinda like this:


Next, some measuring: You want to know where your control arms are when your car is at ride height so you can replicate that when you go to position your new shock mounts. I think I measured from the top of the upper control arm straight up to the inside of the fender. Used a level to make sure I measured straight.

Now Jack your car up, take off the wheels, and face the situation. Probably looks kinda like this:


sigh...
Now take off the old shock and unbolt (newer formed sheetmetal style control arm) or cut off (older forged gooseneck style arm) the old upper shock mount stud.

Take a deep breath and follow me to the next section. I've also never posted anything this long before, so I'm gonna break it up.

 

OK- we're back.
Your new shock mount is gonna need to go on the frame rail just in front of the triangle-ish plate that mounts the steering box. This spot would be easier if you hadn't welded that backing plate to the new upper mount, but those frame rails are actually pretty thin steel, and if you weld the upper mount on edge straight to the rail you run the risk of it doing a "Can opener" on your frame.

Clean up your frame from the steering box plate up to under the control arm. Yeah, do it all now- you'll be glad you did. This pic is of the passenger side, but you get the idea...




Now it is time to get out your new shocks, 'cause the eyeballing and mocking-up is about to begin.

A variety of shocks can work for this. I used a Monroe 3033 (O.E. application was 1967-1991 Full size Chevy truck) on my 50 Plymouth, and Pro Shox sm-600 or 500 (sorry, I just can't remember). Both these shocks are pretty long travel. You're gonna need it.

Now take out your springs (CAREFULLY!!) so you can cycle your suspension up and down by hand.

Grab a shock, compress it half way into its travel and wrap a cinch strap around it the long was to hold it at that point. Bolt it to an upper shock mount.

Now block up your control arms at ride height and start eyeballing where things will go. On the 50 I had to weld the lower shock tab to the lower control arm to get the shock to run straight, on the 38 I was able to use the original position with just a little reinforcement. Either way keep in mind that the shock needs to move straight on its axis. Those mounts have to line up right, and the upper and lower limits of the arm's travel (@ the bump stops) must be less that the travel of the shock by maybe 1/2" on each end.

Once you find where the upper mount must attach to the rail and mark it (as above) you'll have to tailor the backing plate to get it to lay flat against the frame rail. I used a framing hammer and a bench vise to get that gentle curve...


Then clamp it in place again, step back, scratch your ass and think about it for awhile. Cycle the suspension a few more times and make really, really sure you like how you have everything, and weld'er up.


Some cleanup and a little paint and there you are.




Thats the 50 above. the 38 came out prettier but was actually a tighter fit due to the frame and control arm configurations combined with the rack & pinion and discs:


Took me forever to do it the first time, but the second time was done in an afternoon, and made the biggest difference imaginable in handling. This is the best bang for the buck of anything you can do to an old Mopar!

 

Oh- everybody always wants to know how much to cut coils to lower a car a given amount. In the course of doing the 50 I took some measurements :
On the original saggy springs cutting 1 coil dropped the front 1.5" as measured at the frame rail close to the spring.

 

One more thing about the cut springs: New springs from ESPO for the '50 were 17 3/4" long for stock ride height. When cut to 12 3/4" they yielded a ride height 2 1/2" lower, and that is how ESPO does it when you order custom lower springs.

 

wow. awesome tech post. thank you so much. i can't wait to do this.

 

what the disc brake conversion off of?

 

The spindles are original Mopar. I got the disc adapters from "Olddaddy" here on the Hamb. He makes them for a variety of old Mopars.

 

what a great post! this is gonna save me time and $$ when it's my turn
thanks
MIke

 

This rocks!! Thank's man.

 

Not relavent to me right now but since I'm a mopar man this is damn good tech...Thanks!

 

I have a 1939 Chevy with a stock Independent Front Suspension which looks very much like the Mopar suspension in your tech article. I believe that your weld in shock tower concept will work on most Chevy car front suspensions of this era (from 1939 through 1948.
Later!
Specs

 

thanks for all the great info. pics are great and really help... looks like i got another project on my hands...

 

You can also use the Ford F1 F100 Style and either bolt them in or weld them.

 

Bumping this back for tech week.

The shocks plym_46 used are Gabriel 81676.

 

wheres a good place to pick up a set of those f100 style shock mounts????

 

I got mine from Speedway Motors.



http://www.speedwaymotors.com/F1-Forged-Upper-Shock-Mounts,2132.html

 

whats the best length to use on these cars???

 

I don't think it really matters. The length will just change which shocks you'll use. I think I bought the longer ones. I won't know the shocks I'm going to use, though, until I get them installed and start measuring and then go down to the parts store to do some cross referencing.

 

right on, thanks.

 

I'm looking forward to doing this soon, will post pics when done

 

Right On, good info.

 

wow, fantastic thread. good info, nice simple drawings, descriptions and pics. i hope to do this to my 51 plymouth and will use this info to do so. keep it up. i hope to return posting favor on my projects, thx again, mike

 

Well, I did mine, used the F1 shock mounts... worked very well for a year or so, today my passenger side mount broke
Now I'm going to cut some 3/8" plate and get to welding so I don't have to do it again.
Here was the F1 mount... snapped right above the bolts where the heat and bend was applied

 

...should have been bent cold.......

.

 

If you quenched it after you heated it, you screwed yourself. ???

 

It was not quenched after. A cold bend would have held, huh? Well, maybe next time. Glad I ruined some expensive (for what they are) parts.

 

great info i needed this i have a 39 dodge d11 coupe and about to rebuild the front suspension where is the best place to find new bushings also interested in the disc brake swap

 

this will be a must do this summer!

 

I know this thread is old, but I've always wanted to do this to my '47 Ply.

however I wanted to put the shocks inside the coil springs like more modern cars. Has anyone ever seen this done?

 

Way too much work, for no return over what this method offers.