Control arm interchange?

[40plyrod]

Hi guys, it's been awhile since I've posted to this site, life got busy but I'm back and am having a parts interchange problem. I've got a Canadian made 1940 Plymouth sedan and I'm working to install a set of dropped spindles. I'm trying to swap out the upper control arms from the 40 for a set from a later model (1948 I think). I've learned that some of the 1940 Plymouths used a 2 bolt attachment for the upper control arm but mine is a 4 bolt link so the newer style control arms bolt right up however they don't line up with the lower control arm so I can't install the upright. Is there a difference between the 40 and the later lower control arm? Would anyone have an interchange parts manual that can check this for me? Anyone have any experience doing this. I know from doing some research on this site AndyDodge has done this with no issues. Thanks for any help. Ed

[Andydodge]

You called?..........lol............as mentioned my 1940 Oz Dodge is 1940 plymouth based and used the 4 bolt upper A arm which I swapped for the 1941-54 Moog style cast steel upper A arm which uses the 4 bolt inner pin & bushing.........I used the original 1940 vertical spindle with the 1941-54 Upper Outer pin & bush which allowed the spindle to line up with the Moog upper A arm...........the 1940 spindle attaches to the 1940 Lower A arm using the stock style 1940 lower outer pin & bush.............now ......the 1941 -54 stock stamped steel AND the aftermarket MOOG cast steel upper A Arms are HANDED, ie, they must be used on the correct side as their shape is slightly offset front to back.....see the shape of the "X", see how its different on each side? ................have you attached them on the wrong side...............with the inner pins and bushes installed on the upper A arm the pins CAN actually be installed onto the chassis on the wrong side.................see the attached pics which show the non symmetrical shape of the upper A arm........even tho' mine are the cast steel type they are the same as the stock Plymouth stamped steel versions and use the same inner & outer bushes and interchange with the stock parts..............does this help?................Andy Douglas  

[40plyrod]

Thanks Andy for you response, here's a few pictures of what I'm up against. I don't see any offset difference between the left or right upper control arms. The stock 40 upper control arm lines up but the later style is quite a ways out which leads me to believe nothing is bent and I don't think there is enough adjustment in the bushings to get it to match up. That's why I'm wondering if the later lower control arms are different as well.  

[Andydodge]

Plyrod.......you posted 4 pics.....the 1st two, show the upper A arm on the WRONG side as the arm shown has the upper shock mount facing FORWARD........this should face to the rear, like in the 3rd pic which shows the upper shock mount facing to the rear............the 1st two pics show the USA drivers side upper A Arm.........if you note my two pics there is definately an "offset" to the shape of the upper A arm, notwithstanding that the A arms shown are MOOG brand aftermarket A arms they are indentical to the shape of the stamped steel upper A arms of which I have two sets, both sets are offset like the MOOG ones on my car........I havn't access to my workshop manuals at present , its raing & they are in the garage outside but have you checked whether the lower spindle bush maybe inserted backwards?.................otherwise I don't know what to say as my front end is pictured and has been like this since the mid 1970's when i first rebuilt it using these MOOG upper arms..........will check the manuals later & get back..andyd 

[40plyrod]

Yes, I put both drivers side and passenger side uppers on to check alignment but they both are the same and I'm not noticing any sweep difference between the two. Next step is to either get another upper on the chance I have 2 driver's side (one with the shock mount in backwards) or take apart the driver's side and try one over there and see if it lines up. Thanks again Andy for you help.

[Andydodge]

Your 1st two pics show a USA drivers side A arm on the Passenger side, which is incorrect and needs to be swapped.............the 3rd pic shows a USA passenger side A arm on the passenger side, which is Correct................the 4th pic shows the USA stock 1940 Passenger side upper a arm on the passenger side............you seem to have both a drivers & passengers side stamped steel 1941-54 upper A arm, just need to get them on the correct side..............andyd

[40plyrod]

I tried both on the passenger side and took pictures to demonstrate that there was no difference between the two other than the shock mount direction. This leads me to believe that there must be a difference in the lower control arm between the '40 and the '48. 

[Andydodge]

The only different that I've found between the 1940/41 lower A arm and the 42-54 lower A arm is that the 42 onwards has the bracket that the front sway bar end inserts into with a rubber block to isolate the shock.......andyd

[40plyrod]

Thanks for your replies Andy. I'll do a little more trial and error and see if I can get something to work.