What size HEX are the 13/32 pinion bearing BOLTS? 9/16" or 5/8"? Please let me know what year you are referencing.
The bolts the suppliers are making are 5/8" hex.
Not the question I expected. Usually someone is stumped by the odd thread size. The Hex head came in both sizes, but I cannot tell you when which was or why. But this reminds me. I found a few in some T stuff I was sorting through and need to check the boat-tail for which odd head it has. I don't like it when they don't match. The 1920 and earlier using the "closed spool used studs instead of bolts. The nuts also came in both hex sizes. Maybe Royce or someone else can tell which were used when?
Drive carefully, and enjoy, W2
They did make them with both head sizes. I suspect the 5/8 is earlier, because it is difficult to use a socket or a wrench on them. On the 9/16, there isn't a problem.
Lots of cars on this forum have these bolts. Can you please see what wrench fits yours, and post the year of your vehicle? I'm thinking we should be able to establish the transition from the 5/8" to 9/16". Thanks for your help.
I have the smaller 9/16 bolt heads on a 26/27 rear end. My other set of bolts has the larger 5/8 head and was bought separate - may originate from an earlier rear end.
Dave: If you really need to know, get the part number, and contact the Benson Ford Research Center, and request the record of changes. That should answer your question.
Larry, I'm disappointed that the interest in originality is slowly disappearing. I expected this might get some people interested in when this transition took place, since It's easy enough to try 2 wrenches.
Do you remember what you used on your pickup?
I just checked all the cars in my garage. They all take the same size wrench.
Thank you Royce.
Royce: I'm pretty sure David said BOLTS! David, I used the 9/16 bolts on my '25 roadster p/u. You've got me going now. I would like to know too! The 5/8 bolts are difficult to tighten, because a wrench can't be placed straight on, and that is probably why Ford went to 9/16.
Mine are all 1917 and earlier. All 5/8". Maybe they went to the smaller size and bolts instead of studs / nuts when the open spool came into use?
I have examples of the 9/16" bolts on 1926/7 cars, but no examples earlier than that so far.
We need some 20-25 cars to understand this better.
Anyone with a later car can help! please take a minute and see what you have. Your help is greatly appreciated.
There are very few rear axle assemblies that left the Ford factory that are unmolested originals - I would suggest taking Larry's recommendation as stated above - anything else would be insubstantial.
My '23 and '24 have 5/8" head size hex bolts in the open spools, the Bolt Chart with tool identified by Ford part #2584B also lists the nut for the spool stud as 5/8" hex head size for the wrenches to be used on that nut.
5/8" hex wrench to use on the '23-'24 spool bolts.
The confusing part is that the early stud and nut was part # 2584-B, and when the change was made to the cap screw, the same part #2584-B was used! That cap screw also used a lock washer, [ref. Sept 1921 Service Bulletin]
Looking up the part # in Ford books, find that there is no rev. for a smaller hex head (9/16") for the #2584-B.
But a check of the parts drawing or rev notices perhaps might find that in 1926, with the large drum rear axle, that cap screw became a smaller 9/16" hex. My 1927 has that size!
1927 large drum and small hex head cap screw.
So don't know the final answer, both both sizes of hex head seem to be found on Fords
Dan, Your pictures really help highlight the difference. Your findings help support the theory (my working theory) that the 9/16" hex size bolts come sometime between 1924 & 1926. I just had the opportunity to look at a late '21; that had 5/8" hex.
I've wondered what year that diagram was made from. Obviously it lacks the large drum axle and hogs head to block support bolts. It also depicts a magneto horn on the firewall. Interesting that it shows & lists demountable rims, but does not show or describe the generator, starter, or battery carrier. Since it also describes the drive shaft as having studs & nuts; my estimate is 1919 to 1921.
I really want to thank you for taking the time to take the photos.
I assume that brass tag lets people know you have the coveted brass bushings in your rear end?