Castellated nuts on La Salle bumpers

[John Barry [CLC17027]]

My '40 La Salle has castellated nuts holding the rear bumper in place. While these may be used with cotter pins or similar devices to ensure things remain in place, there are no cotter pins used here (or any other securing device). I'm puzzled as to why castellated nuts would be used like this, as opposed to (let's say) a hex nut with a class 3 or class 4 fit.

[Alan Harris CLC#1513]

Interesting that you would bring this up. My 1940 LaSalle 5219 has the same castellated nuts on the rear bumper. I always just assumed that they were put there by a prior owner because he had them handy when he was installing the bumper. Now it appears that the car came that way. There are no cotter pins nearby. Very strange.

[John Barry [CLC17027]]

Precisely my reaction, and precisely my situation also. The use of castellated nuts and the absence of cotter pins makes no sense from a mechanical or financial point of view.

[Warren Rauch #4286]

   I think the answer is to look at the standard hardware that Cadillac used. The parts book  (group 25.0080) calls for just a plain nut # 11.0823-120371 (1/2x 20 ,7/16 thick, cadmium plated) . Now look at group 25.0088. Lock nuts. There is a nut 1/2 x20 ,7/16 thick. It looks like a castle nut,but it would have a reduced diameter on the top to make it lock. No cotter pin needed. A dealer repair or a running change?
I'm guessing dealer.If Running it should be noted in the parts book.

Warren

[Classic]

I believe these were early versions of all-metal locknuts.  Not sure what they were called.  They were not meant to be used with cotter pins.  Not available today as far as I know.  They were used in several places on my '37 Cadillac's. Someone correct me if I'm wrong.

Gene

[John Barry [CLC17027]]

Fascinating. Sounds like the strategy for replacing a bumper would be to do one's utmost to save the old castle-style nuts. Failing that, the next best approach would be latter-day ½"-20 UNF hex nuts and lock washers. I don't think there's room between the bracket and the body to allow the use of an impact driver.

[Warren Rauch #4286]

     With as many cars as have them, it made me ask why. In the Serviceman March 1940, page 11,titled Rear Bumper Installation may be the answer.Some LaSalles when shipped by rail had the rear bumper removed to fit in the rail cars. The dealers had to reinstall them. If the bolts/nuts were lost ,new parts from stock would be used. Right?  Warren

[David King (kz78hy)]

I would check the master parts list (bumpers) and see what nut was called out.

[Brad Ipsen CLC #737]

I believe these are called Marsden nuts and are the normal nut on Cadillac bumpers in 1940 plus and minus years.  Not sure the total years used.  These types of nuts are scattered throughout the car.  The shock arm nuts are same style.  Also there are various 1/2" hex nuts (5/16 fine thread) used in various locations.  The bumper nuts are the ones that show and if not there a sure sign that care has not been taken in restoring the car.  Parts were lost.  Group no. 25.0088 in the parts book.

[Roger Zimmermann]

Those nuts were also used later: the flywheel from the 56 and maybe 57 Hydramatic transmissions is also attached to the fluid coupling with such rather small nuts. If screwed/unscrewed several times, the self retaining power from the nuts is getting almost to zero.
The nuts were also used on four studs locating the engine oil pan on those cars.