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--- techtalk:ih:transfinal03f [2022/10/04 01:54]
hippysmack [1977-E1979 Trapdoor]
+++ techtalk:ih:transfinal03f [2024/04/29 19:53]
hippysmack [1957-1985 Transmission Trapdoor Pics and Information]
@@ Line 3: / Line 3: @@
 ====== 1957-1985 Transmission Trapdoor Pics and Information ======
+\\
+====== Transmission Trapdoor History ======
+The first transmission door appeared in the mid 1954 model year. ((Dr Dick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/204280-trans-door/page8#post4590222)) \\
+Previous to that you would have to split the cases to do any transmission repair. This was not popular with dealers. \\
+The dealers were Harley Davidson's customers: It wasn't you and me. So what the dealers had to say had carried great weight with the Motor Company. \\
+Transmission failures in the K models was a common occurrence. HD wood upgrade transmission changes almost immediately after the introduction of these models. These changes would continue until 1958. While Harley was trying to figure out how to keep these transmissions together, the dealers needed to be able to get into the transmissions to fix them. What that did is required HD to design and install what they called an access cover. We know it as the trans door.
+The Japanese and Europeans would also adopt this access cover technology for the race bikes. They call them cassette transmissions. At the racetrack, you could now remove one transmission or replace it with another which meant gear ratio or transmission changes were quick and easy. \\
+The mid 54 through 1956 trans doors were attached to the cases via tapered dowel pins. This require hand fitting. Harley-Davidson must have been concerned that the trans door itself would become a issue and transmission failures. It didn't.
+in 1957 the first interchangeable doors were introduced. Straight dowel pins . These doors remained unchanged until 1973. At that point the countershaft bearing area was reinforced.
+In 1975 HD was in the process of swapping these bikes over to left hand shift if you if you look at a 77 and up model crank case you'll see that the casting numbers are dash 75. For the 1977 model year the door was changed to accommodate the left hand shift shaft and the demise of the transfer valve. This door had the notch for the shifter shaft and a modification of the bottom profile of the door. The shifter shaft notches self-explanatory. The change to the bottom profile of the door was to allow the transmission and primary to share the oil. There is now a open area under the counter shaft were oil could migrate between the two compartments .
+previous to this in 76 and down models the transfer valve allowed the transmission to fill up with oil when the bike was idle. with your 76 down bike once the transfer valve evacuated most of the oil out of the primary the trans remained basically isolated so the idea being that the trans kept getting lubed. Without the transfer valve in 77 there was no need for this any longer it was actually thought that it was better off that the primary and trans shared the oil all the time. this is the door was supplied through the parts department as replacement for all 57 and up bikes. I've never found the problem with using these later doors on a 76 and down motorcycle HD also used them on under XR's built after 77.
+Bottom line is that any sportster with a generator can interchange any generator vintage door on any generator vintage bike.
 ====== 1977-E1979 Trapdoor ======
 HD Part# (34844-57B) \\
 Casting# (34846-76)
+Machined cutout for left side shifter shaft protrusion. \\
 -E1979 Sportster Transmission Trapdoor Pics: \\
@@ Line 17: / Line 43: @@
 HD Part# (34847-79) \\
 Casting# (34846-76F) \\
+Machined cutout for left side shifter shaft protrusion. \\
 L1979-E1984 Sportster Transmission Trapdoor Pics: \\

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