Twist That Early 5-Speed Into A Smooth,
Modern Performer!
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| When Harley made the move from
four to five-speeds in 1984-85, it began a process
that wouldn't be finalized until 1991, with the
transition to a splined output shaft to replace
the keyed taper shaft that was prone to breakage. |
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| Converting your 1985-1991 five-speed to a modern
day TwistGear/WideGear setup is easier than you
think. |
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Adapting TwistGear and WideGear to
Older 5-speeds
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| Both TwistGear and our new WideGear
30mm extension are easily retrofitted to 1985-1990
BT 5-speeds, resulting in major increases in reliability,
performance, and comfort. Harley-Davidson's 5-speed,
introduced in 1984-85, retained the traditional
key and tapered shaft design joining the clutch
hub to the transmission. The key tended to shear,
usually in direct relation to available horsepower
and torque, the spacer seal was easily damaged during
installation, the main shaft bushing was prone to
leaking, and servicing required case removal.
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| In 1991 the splined mainshaft design
was introduced, which not only strengthened the
drivetrain components significantly, but made servicing
the clutch and transmission much easier as well
— a definite improvement all the way around.
Ball bearings replaced the needle bearing supporting
the main gear, while the old style main shaft bushing
was converted to needle bearings and sealed with
an interior oil seal.
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| To convert the old style 5-speed,
you'll need a splined main shaft and clutch hub,
along with your preferred clutch. You'll also
need a transmission output sprocket to go with
theTwistGear or WideGear kit you're installing.
You may also want to invest in a late model trapdoor
that can take advantage of the larger bearings
used since '98. To the best of our knowledge,
the following OEM part numbers can be sourced
for the conversion. Other versions are available
from the aftermarket. |
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| PART |
P/N |
| clutch hub |
37550-98 |
main shaft
(not required with WideGear) |
35042-91 |
| transmission
sprocket, 32T |
40250-94-A |
| compensator
sprocket, 24T |
40269-85 |
| compensator
sprocket, 25T |
40308-94 |
| clutch shell
and sprocket, 37T |
37707-94 |
| clutch shell
and sprocket, 36T |
37707-98 |
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Why is it a system?
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| Our improved spacer and oil seal
are also major improvements that result from upgrading.
The old spacer design (see our new, improved version
for four-speeds that combines spacer and seal) was
wide, with a small, fragile cross-section and minimal
lead-in chamfer, creating a lot of difficulty during
oil seal installation. Further degrading longevity
are the narrow transmission sprocket splines, which
generate high spline stress.
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| The 1994 sprocket upgrade is wider, allowing a
large diameter narrow spacer that in turn allows
a bigger lead-in chamfer. The end result is reduced
spline stress and easier seal installation. Our
spacer, included in the TwistGear kit or available
separately, has a lead-in chamfer twice that of
the 1991 OEM spacer, speeding installation and reducing
the potential of installation damage. |
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| Our oil seal design is different as well. All
our helical system upgrade - TwistGear, WideGear,
and SportGear - kits include our exclusive triple
lip oil seal, which can also be purchased separately,
as can our alloy spacer. If you're considering an
overhaul, now's the perfect time to upgrade both
the reliability and performance of that vintage
tranny. It's easier than you think, and better than
you could imagine.
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What About Four Speeds?
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| As for four-speed frames, there are
several manufacturers of "five into four"
cases that fit square swingarm frames and accept
trapdoor cassettes. Although we haven't tested them,
we see no reason why they wouldn't work. Disclaimers
usually include having to retro back to a tapered
mainshaft, but in order to use TwistGear, you'd
do the opposite and fit a splined late model mainshaft,
which would also affect the rest of the drivetrain,
including the clutch hub. |
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| There's also the issue of shifter
linkage and cable routing, but all in all it looks
like a relatively easy workaround that can bring
modern technology to those old Shovels, Pans, and
Knucks. We're currently developing sources for riders
who don't want to give up their classic rides in
order to benefit from modern five-speed transmission
technology. |
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SportGear™ and TwistGear® are
trademarks of Johnson Engineering,
Inc. Buell™, Dyna™, and Sportster™
are trademarks of the
Harley-Davidson Motor Company. No affiliation
with the
Harley-Davidson Motor Company is implied or
inferred.
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