H-D Big Twin round-tube swingarms 1958-72
Description: Round-tube swingarms were used as original for 1958–64 Duo-Glides, 1965–72 Electra-Glides and 1971–72 Super Glides.
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Round-tube swingarms were used as original for 1958–64 Duo-Glides, 1965–72 Electra-Glides and 1971–72 Super Glides.
1958 (early?): Was a prototype swingarm used on any 58 model production Pans? I do not know. In Bruce Palmer’s 37–64 FE it said early-58s have a prototype swingarm but in his 37–64 SE it says perhaps very early 58s have them. Anybody know for certain? According to Palmer the prototype swingarm had forging number EX2040 outside the left axle clip and forging number EX2039 outside the R-H axle clip. I have no clear photos of these markings but page 976 of Palmer’s 37–64 SE shows what may be EX2039 on a 58 prototype Pan.
1958: Even if some early-58 model Pans had a prototype swingarm I imagine the majority of 58s would have received the first BT production swingarm. These had forging number 47614-58 outside the left clip. Also present was a forging hallmark consisting of the letter A inside a shape that looks like a jar. According to Palmer this hallmark indicates AmForge, Chicago, Illinois. In the first picture below, hallmark A is followed by die number 1. Under the forging number is 64 and apparently this represents the production run. This is the lowest run number I have seen on a left clip that has its forging number outside. Also notice the position of the threaded hole for the brake hose clamp bolt (H-D #3720).
The bolt hole is accommodated by a semi-circular boss inside the clip.
Next is another swingarm with 47614-58, hallmark A, die number 1 and run number 64 outside its left clip.
Outside its R-H axle clip is forging number 47606-58. Away to the right is die number 1. Also outside the clip you will often find a hallmark that looks like the letter Q with WF inside but it’s hard to be sure it is present in this picture.
The next swingarm is a later model and provides a clearer view of the hallmark although it is not always in the same position.
While forging number 47614-58 was still outside the left clip, 65 was another run number that accompanied it. Hallmark A is present as is die number 1.
I don’t yet know what happened with run numbers 66–69.
Some will recognise the next two pictures because I have used them before. Forging number 47614-58 and hallmark A are both present but the die number is 2. I cannot see a run number.
Inside the clip appeared to be an additional rib and I wondered if it was original to the swingarm but it was hard to be sure because the view below was the only one I had.
Next example has the same forging number outside its left clip, along with hallmark A and die number 2. This is the highest die number I’ve seen outside a left clip. I cannot see a run number. This clip is further similar to the previous one in that it has an extra rib inside.
However, in that instance the rib appeared welded on and I have pictures of another swingarm showing the same thing. That gives me three examples of swingarms with 47614-58 outside and an additional rib inside. At least two appear welded on but I still don’t know if the other one was welded on or was part of the forging.
1959 (early and mid): It seems most 59 model Panheads had swingarms with forging number 47614-58 outside the left clip but did the forging ever include the abovementioned extra rib as original while the forging number was outside? Anyone?
1959 (late?): I think it may be possible some late-59 Panheads had swingarms with forging number 47614-58 inside the clip. I have seen this with a few 59s and the swingarms may be original to the bikes. The semi-circular boss for the brake hose clamp bolt is present, as is the additional rib, but the extra rib is not welded on; instead it is part of the forging. And the forging now includes extra material along the bottom of the clip. Hallmark is A. In this instance the die number is 3 which is the lowest I have seen inside a left clip.
Outside the clip is run number 71 upside down.
Next picture provides a better view of the extra rib and again it is part of the forging. Inside is 47614-58 with hallmark A. I am unsure about the die number.
Run number outside looks like 70 upside down.
Generally speaking, die numbers and run numbers got higher as time progressed but the combination of numbers on some swingarms indicate the forgings were not always used in the order in which they were produced. Always check as much ID as possible.
1960–61: Panheads for these two model years had the same type of swingarm that I think may have first appeared on some late-59 Pans. Below is another example with forging number 47614-58 inside accompanied by hallmark A but the die number is 4.
Run number outside is 74.
Outside the R-H clip is forging number 47606-58 as expected. The hallmark appears present and to its right is a die number that may be 8.
The third die number I have seen inside a left clip of this type of swingarm is 5.
Run number outside is 76 but it is preceded by what looks like the letter L. I do not know what L indicates.
As mentioned earlier, 3 is the lowest I have seen inside a left clip and I think it possible this type of clip may have first been used for some late-59 Panheads. I do not know exactly when 3 changed to 4 or when 4 changed to 5 but it seems that 5 may have been the last die number inside the left clip for 1961 models (and perhaps the first for 1962 models).
1962: Similar to 60–61 but in the section that accommodates the pivot bolt there is a grease fitting as original. It is mentioned in my 1959–69 H-D SM on page 2F-14: ‘1962 and later models have grease fitting in fork pivot housing.’
On that page (2F-14), figure 2F-20 indicates the fitting is on top of the housing but that seems wrong and although I have seen one fitting on top I do not think it was original. Anybody know if the factory ever installed a grease fitting on top as original? Does anyone have a copy of The Enthusiast introducing 1962 models? If so, could you check it for any mention of the fitting and its location. Thanks.
Other swingarms I have pictures of show the fitting underneath and placed as per the next example. Ahead of the fitting is a forging number that looks like 47556 58. It is followed by a hallmark and I’ll come back to both these markings later.
Inside the left clip is 47614-58, hallmark A and die number 5. As indicated in my previous post, 5 was perhaps the first die number inside the left clip for 1962 models (and maybe the last for 1961 models).
Outside the clip is a run number which looks like 81 upside down.
1963: Forging number inside the left clip changed from 47614-58 to 47614-58A. Hallmark is still A. On the next example the die number is 7 which is the lowest I’ve seen so far on a forging with 58A. (I have no examples yet with die number 6.) Notice the difference in two inside ribs when compared with the previous swingarm. No semi-circular boss for brake hose clamp bolt #3720 (used 1958–62); instead there is now a rectangular boss to accommodate screw #2672B, resulting in the fastener hole being further forward and closer to the bottom of the clip.
Between the top of the shock stud hole and the boss for the axle adjuster bolt, material was added and the outer edge takes on the appearance of a reinforcement rib. About halfway down the clip, a rib was included and it extends most of the way across.
Another picture I have of the above swingarm appears to show two pressure release holes at the front of the pivot bolt housing but it is hard to be sure. However, the holes are visible in the next swingarm and it too has 47614-58A, hallmark A and die number 7 inside its left clip.
As indicated above, forging number 46714-58A officially first appeared for 1963 models. And the same seems to apply for the twin release holes. Did any late-62 models have swingarms with the 58A forging? I am not sure. I have photos of a few late-62s with them but I do not know if the swingarms are original to the bikes.
1963–65: It may be that run numbers outside the left clip reached their highest at some point during 1963 or perhaps during 1964? Run numbers seem to have commenced in the 60s and continued into the 70s, 80s and 90s but I suspect they went no higher than 100 and may have then gone to H1? I haven’t seen H1 or H2 but one of my mates has H3 upside down outside the left clip of his early-1965 Panhead and I’m thinking this was the new style of ID to represent a production run. Can anyone confirm this? Or if anyone thinks it is wrong then please comment. Anyway, the swingarm appears to be original to the bike so I imagine the letter H may have first appeared prior to the 65 model year. The bike was assembled when he bought it and still is so we don’t yet know the die number inside. Outside his R-H clip is die number 28 upside down.
Apart from the abovementioned change for production run number ID outside the left clip, it seems swingarms for 63–65 are the same type. Next example has H4 upside down and I suspect it may be a 65 model although I cannot be sure.
Inside is 47614-58A and hallmark A but the die number in this instance looks like 8.
Outside the R-H clip the die number is 27 upside down with a hallmark below it.
1966: Same type as 1965. As noted earlier, the combination of die numbers and run numbers on some swingarms indicate the pieces weren’t always used in the order in which they were made so I can’t be certain about some model years. Anyway, the next highest I have seen outside a left clip is H7 upside down.
But the die number inside is still 8 as per the previous example.
Next combination is H8 upside down and die number 9 inside.
1967: Left forging number is 47614 58A. Hallmark A is present. I am not sure when the left die number changed to 10 but it seems to be around 1967. As per earlier clips, some die-10 clips have only one hole for the brake hose clamp screw but some have an extra hole further to the rear. Also notice below that there is no boss for the additional hole.
And here’s another example.
It may be that early-67s only had the hole in the rectangular boss first introduced for 63 and my guess is most swingarms for 1967 had that hole tapped ready for use. But at some stage during the 67 model year it seems the factory wanted the hose clamp mounted further to the rear and that may be why some swingarms have two holes. I expect very late 67s only have the rearmost hole, as do 68–72 models. For those swingarms the rectangular boss remained in place but it did not have a hole.
Something else that seems to have changed around this time was the placement of the twin pressure release holes in the pivot bolt housing and you’ll notice the two below are closer together than the holes shown in the black swingarm earlier in this thread.
However, one swingarm I know of only has one release hole although it is in one of these later positions.
As another example of pieces not necessarily used in the order in which they were made, some clips with die number 11 still used the brake hose clamp screw hole in the rectangular boss.
I think clips with that die number (11) may also have been the first to have the boss left undrilled but pictures I have thus far are not very clear.
I do not know when the left die number became 12 but the forging number was 47614-58A. As you can see, the only hole for the brake hose clamp screw is the one toward the rear that seems to have first appeared at some stage during the 1967 model year. The rectangular boss introduced for 63 remains in place but has no hole.
Next change to the left clip forging number was when it became 47614 58B. Hallmark is still A. In this instance the die number is 13.
Outside the left clip is H22 upside down. Notice the lower rib has been increased in length and ends closer to the anchor stud hole than before.
Getting back to the pivot bolt housing, I do not know if any were made with an EX (experimental) forging number. All the ones I know of bear a forging number that looks like 47556 58 and it can be found below or above the housing for 58–61 models. Usually the forging number is followed by a hallmark but it’s hard to get a clear picture of it. Anyone know for certain what the hallmark is?
For 62-later models I have only seen the forging number below the housing. The same hallmark was often there although I’m not sure how long it remained.
Some late-60s–72 housings have other markings underneath such as 4-H, 4-N, 14-N and HH but I don’t know what they indicate. On top sometimes you’ll see a lone number and these go from 1 through at least 4.
Questions and/or comments welcome regarding any of the info I posted. And if anyone has a swingarm I can help ID then please feel free to contact me anytime.
Also thanks again to panhead (Site Admin) for your help with forum settings.