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While visiting our pals at Rivera Primo in Whittier, California, amongst the belt drives and SU carburetors, we spied a fully polished jewel of a six-speed bagger transmission. Wanting to know more about the Powerdrive 6-speed LSD ($1,949), Ben Kudon, the marketing whiz at Primo, walked us through the technology behind its newest tranny and offered one up for an install. The transmission is made for upgrading '93-98 touring bikes to six-speed, but we wanted to make it work on our project '89 FLHS. Doing this would get rid of the FLHS's bulky frame-mounted oil tank and make room for upgrades such as an air ride compressor and controller.
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To get things started...
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To get things started H-D tech, Kevin, removed the rear wheel.
We couldn't get the straight dope on whether this or any other late-model touring transmission would fit on this old frame, so we decided to man-up and try and get it to work.
Basically the transmission is comprised of parts completely made in America. The case is made from a single chunk of billet aluminum that is polished to a mirror-like finish. Yes, it may be a sweet-looking tranny, but it's what's inside that's the real thing of beauty. Packed into the case are six forged gears, which are all back cut for durability and easier shifting. The 2.94:1 First gear leads way to a 2.21 Second, 1.60 Third, 1.23 Forth, 1.00 Fifth, and an 0.860:1 overdrive Sixth. This gearset was chosen by Primo after much testing and they found it to provide great off-the-line acceleration while offering smoother cruising at high speeds. Also in the case are hardened shafts as well as support blocks, a billet oil fill tube and top cover, and grade-8 hardware to hold it all together.
After taking the bike to Harley-Davidson of Anaheim Fullerton, we found it only took a little forethought, as well as some slight modificatins to both the new transmission and the old swingarm, to get it to fit. Follow us as we show you how it was done.
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The swingarm, which holds...
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The swingarm, which holds the rear of the trans in the frame was also removed.
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The front of the trans...
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The front of the trans was unbolted from the rear of the engine and removed.
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The stock trans (left)...
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The stock trans (left) has a bulky bolt-on oil tank that is housed in the frame of the bike, where as the Primo trans (right) has the oil tank neatly built-in like a late-model Harley.
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Kevin checked the fit...
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Kevin checked the fit of the swingarm on the bench to make sure it didn't bind and had enough room to fully articulate without hitting the new trans.
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We found that the top...
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We found that the top and bottom of the front of the swingarm had to be clearanced with a die grinder a few thousandths to fully clear the new trans.