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Does anybody know the thread of the steering box filler plug on a 1951 coupe. I'm across in the UK and it doesn't seem to be a standard UK thread.
Eric.
I'd guess it's either US Standard or NPT as they did not use metric back then on anything. @CarlNutaitis or @GaryDubas maybe it's the same as your '48 or '49 and you can help confirm what it is?
I'm not the club's '51 expert though I can report on what my '46-'54 MoPar parts book show. The parts book suggests that the only '51 models to use a filler plug for the steering gear housing were DeSoto and Chrysler Windsor (6 cylinder). Further, there was a running change by s/n that suggests after certain s/n's there was no filler plug. There are no filler plugs listed for any MoPar models in '52 until they reappeared in '53. The MoPar p/n for the '51 filler plug is 1142221. Apparently, that part resurfaced and was used in the later fifites on cars with manual steering. If you search eBay for that p/n, you find several examples listed for the later model application: https://www.ebay.com/sch/i.html?_nkw=mopar+1142221&_sacat=0&_from=R40&_trksid=p4432023.m570.l1313
None are very expensive so maybe worth a try. Hope this helps.
@ericwalker I own a 1941 & 1948 DeSoto. Both have a Gemmer 3 manual steering gearbox. The steering linkage/tie-rod configuration changed quite a bit with the introduction of the 2nd series 1949 DeSotos. Also, DeSoto started offering power steering in the early 1950's, but I'm not sure of the exact year. I caution those two points with you first, but the dimensions of the plug from my cars are as follows.
Directly from the 1946-48 DeSoto parts manual, it says the filler plug is SAE straight thread 3/4"-20tpi x 17/32. The actual threaded portion of the plug is only a 1/4" inch. The 17/32 inch length is not critical. However, I would recommend that you try to stick close to the threaded portion length of 1/4" inch, as anything too much longer would have the chance of interfering with the steering gear sector shaft inside of the steering gearbox when you screw in the plug.
Here are some pictures for a visual reference:
Again, I cannot say with 100% certainty that the plug dimensions are the same for a 1951 DeSoto, but if hole where the filler plug is located on the cover plate on your car looks similar to mine, it is worth a try!
