Built a home brew jig for the lower control arms

[Noonan]

Built a tool yesterday to assemble my lower control arm and torque the lower inner control bar bushings on the 40.   Heres what i did. 

 

I took a good known front suspension from a 51 desoto.  Measured the 51 lower control arms and control arm bar as an assembly.   i found the measurements matched exactly from left hand to right hand control arms.   I felt it was a safe bet to make a jig from this.  

 

Once I transferred my completed jig over to the 40 control arm I found that these old arms had been cranked in without a jig in the past (1/8 - 1/4" approx).  

 

  I used a floor jack to spread the arms and install the jig.  Torqued the control arm bushing to 150ft lbs.  Life is good. 

 

Edited March 14 by Noonan
Pics

[andyd]

Nice work on the tool.......I have a question tho' regarding the spring pockets on the A Arms........are you running airbags?.........andyd

[Noonan]

Yea it is ! I've got it set up on air bags on all 4 corners

[Saskwatch]

  On 3/14/2025 at 7:06 AM, Noonan said:

Yea it is ! I've got it set up on air bags on all 4 corners

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        This sounds very interesting Noonan ! 
  I for one , would be very interested to read of how you do this ,if time allows. 
   Thank you 👍

[Noonan]

There's no rule book, it was a first for me.  Lots of measuring and planning.  Lots of fit up followed by re measuring/tweaking. 

   

Explaining everything could get heavy but here's a quick overall. 

 

I used the factory 40 axle in the rear, built a triangulated 4 link using a combination of heim joints and bushings.   clearanced the frame rails for the axle just enough so the axle rests on the frame at the desired lowest frame height (it cant go any lower) 8" pacbrake air bags in the rear.   

 

Set the rear ride height with the bags at 35 psi.   Set the ride height with the front bags at 65 psi.   I did my best to determine the overall airbag height at my pre determined psi before I started mounting and building anything 

 

Used the factory front suspension.   lowered the knuckle supports for a static ride height drop.  I had some 7" pacbrake air bags and mounting plates left over from the rear of a toyota pickup i used that in the front to start setting up the bags.    Pacbrake air bags are solid and affordable up north here.   

 

 I'll have to get some photos together. 

 

The steering is all factory and connected, swapped steering arms from left to right.  Gave one arm a little heat up and bend.   Steering may need to be improved and tweaked, time will tell as things progress.   I will have to tighten up that loose old steering gear box yet.  

 

And on and on and on 

[Saskwatch]

     Thank you very much , a lot of impressive work, you must have done this before.

 As always, those pictures would be appreciated.

 Also, a shout - out to andyd for picking up on that and inquiring about the airbags just by reading the post & pictures ……. Thank you for the interesting post!  👍👍

[Sniper]

Nice work on the jig, the FSM have for my Plymouth does give those measurements as a double check, not sure if they are the same as a Desoto's but I imagine the Desoto manual would have those measurement too?

[andyd]

Saskwatch.......I've been wearing glasses since I was 13, now 71........so I have 4eyes........able to see things....lol......andyd 

[Noonan]

  On 3/15/2025 at 7:11 PM, Sniper said:

Nice work on the jig, the FSM have for my Plymouth does give those measurements as a double check, not sure if they are the same as a Desoto's but I imagine the Desoto manual would have those measurement too?

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I did check the measurements from the fsm to the 1940 control arm after building and using the jig. 

 

 I had to get a bit creative when transferring over visible marks to use those measurements.   The points used for measuring the overall span are not taken from the outer edge of the control arm,  they are taken where the control bar bushing contacts and seats.    If that makes any sense.....  It's as if it's a cut away view. 

 

The 1951 car these arms came off of looked like it hadnt been messed with.   I was assuming these control arms had never been apart.  

 

 Comparing the inner control bars and bushings from 1940 to 1951 they are the same parts.  So I also assumed the control arms would have the same specs as well.  

 

   Assumptions can be horrible things lol...  you only live once... 

 

I did not use any measurements to build the jig.    I built the jig right on the 51 control arm. 

 

Used bolts in the control bar holes as my locators for the control bar location front to back. 

 

2 pieces of angle iron.   These were clamped and secured then tak welded to the bolt heads.  Finally flat bar spanned the gap.   

 

Could have built it out of one piece by making 90 degree bends in the press although the angle iron has the inner webbing that kind of looked like the factory tool.

Edited Sunday at 05:38 AM by Noonan

[MikeMalibu]

Thx for adding the tips on making the tool.