1940 Plymouth upper control arms.

[Randy4840]

I have a question about upper control arms on my 1940 Plymouth Convertible. I am in the process of installing Fatman dropped spindles designed to fit the 51-56 Mopar's. I read on this forum that the 41- 56 upper control arms would fit in place of my stock 40 upper control arms.My stock control arms attach to the upright from just one side. The 46 upper control arms bolt on but the upright doesn't line up correctly with the newer control arm. Anyone tried this conversion with any success?

Thanks.

Edited October 28, 2019 by Randy4840

[Andydodge]

Randy........I have a 1940 Oz Dodge 4dr Sedan which was based on the US sourced 1940 Plymouth, apart from being RHD it is the same as the US 1940 Plymouth chassis and I have used MOOG cast steel upper control arms on it since about 1973/74...........I have the Moog 1941-1956 upper A arms with the 41-56 upper inner pins and bushes and the 41-56 upper outer pins and bush.......the original 1940 Upper Inner pin uses 4 bolts to attach to the chassis the same as the 1941-1956 Upper inner pin.........I have used the stock 1940 Spindle that the 1941-56 bush fits into  without any problem..........the lower A arm is the original 1940 A arm and likewise the lower inner pin and bushes and out pin and bush..........I use 1941-56 stub axles with the 1939-56 king pin ......the car has a 9" shortened Austin 1800 Rack & Pinion.............I have a 1' thick Heim jointed adjustable sway bar using the lower shock mount pin as per original 1940, the sway bar is located at the chassis with neoprene bushes.............I have also only this year relocated the upper shock mount using a custom made upper mount as pictured...............my car runs 11" Oz vented disc and 11" solid rear discs..........apart from the relocated upper shock mount everything described has been this way since the mid 1970's, I have owned the car since 1971, the V8 I installed in 1973.............I trust this helps............Andy Douglas        

[Randy4840]

Andy, thanks for answering my post. My 40 convertible has the single side upper pin attachment. I tried a 47 Plymouth upper control arm but it doesn’t line up properly. Bolt pattern mount to the frame is correct. The upper pin is a different diameter so it wouldn’t fit the upright. I have a set of Fatman Fabrications 3” dropped uprights to fit the 51 to 56 Mopar. They are similar in all but the upper pin diameter. Your pictures are most helpful. Thanks again. I am new to this site and haven’t figured out how to post pictures yet. 

Randy Cole. 

 

[Andydodge]

Randy............the upper A arms I used whilst they are Moog 1941-56 aftermarket replacements use the standard stock 41-56 inner and 41-56 outer pins and bushes..........the stock mopar upper A arms are stamped steel and are the same dimensions as the Moog pieces ......I am using the stock 1940 Oz Dodge spindle or upright which is the same as the 1940 Plymouth and as the pics show the upper outer stock camber bush and pin fit both the 41-56 upper A arm and the 1940 spindle or upright.............in the 4th pic down you can see that the upper rebound rubber on the A arm does not quite line up with the rebound rubber plate on the chassis tho' it is sufficient to work but apart from that the swap/conversion does work............I recently did the upper shock mount relocation as shown in these pics tho' I am not absolutely happy with the change in handling.........the sway bar arrangement I have on the car has been there since the mid 1970's and as shown uses the original lower shock mount pin as per the stock 1940 arrangement tho' with aftermarket Heim joints ...............you mention that you have Fatman uprights which still should use the stock mopar upper and lower outer bush and pins which should be the same as the standard upright in those areas............andyd  

[Randy4840]

Andy, thanks for your patience with me on this subject. In talking with Fatman about the uprights, I learned that there are 3 different upper outer pin sizes on the 40. Mine are smaller than the ones on the 41 outer pins. For now I am going to use my stock upper control arms with the Fatman dropped uprights. Knowing what you have told me I will look for the upper control arms that fit my car and have the correct size outer pin for the next phase of this build, which is to install a 57 Red Ram 325 Hemi. Next year. For now I am lowering this car and installing disc brakes on both ends. 
I am interested in what you used for your sway bar. I am sure the stock one is too small. I have a custom one on my 48 that is 7/8 “ diameter. I will call the guy that built the one on my 48 unless I can source one from a different car. Any information on yours would be appreciated. 
Thanks, Randy 4840

[Andydodge]

Randy..........the only 1940 parts on my cars front suspension is the spindle or upright, the lower A arm and its inner & outer pins and bushes.........ALL the upper parts, A arm, inner & outer pins and bushes are 1941 to 1956 parts and fit fit without modification to the spindle upper hole..........I used the 1941-1956 parts as I found the Moog cast steel arms and as they are a generally stronger piece than the stock 1940 Dodge/Plymouth upper A arms I used them..........as for the sway bar I used Heim joints as the sway bar I had made by a local Oz aftermarket suspension company, it is the same overall shape as the stock bar but 1" in diameter, with each end flattened with a hole drilled thru it, the Heim joint bolted on and the link between each Heim joint was machined up from hex bar by a friend, the lower shock "pin" was also machined with the stock shock on one end and the Heim joint on the other........the 7/8th sway bar should probably be o/k..........I just back then thought 1" sounded good........lol...........andyd   

Edited November 3, 2019 by Andydodge

[rich-d]

some one on ebay is selling x style control arms for '39-'40 cars. Pricey about $185 each side. I'm thinking of getting them because they look stronger that way. These cars are being driven at higher highway speeds and have more power these days.

Edited January 26, 2024 by rich-d

[andyd]

The thing you need to be aware of is that whilst the 1939 upper arms look the same as the 1940 ones, the 1939 upper inner pin/bush assembly uses only 2 bolts to attach it to the frame, whereas from 1940 to 1954 at least they use 4 bolts.......I'm not 100% sure whether the 1940-56 arms will fit on the 1939 bushes & pins.......its been a while since I looked at the differences between the years........andyd