February 24, 2003
Smoother, Stronger, Quieter!
and Manufactured Exclusively in the USA!
you ride a five-speed? As a professional Harley mechanic, I’ve
heard all the “Go Fast” hype on every engine and trans
combo you can imagine, but I’ve seldom been satisfied when I
used them in my own bikes.
When TwistGear caught my eye I decided to try it in my Roadglide®
95-inch TC. The close ratio 1st – 4th gear gave me a hole shot
that really surprised the Hot Dogs I ride with, but 5th gear's the
same as always.
In plain talk, I was just as quick as the guys with the smaller sprockets,
but at 85 mph I was loafing along at 3,400 rpms while they were spinning
like crazy at 4,000!
really works – I highly recommend it to anyone who wants real
performance without sacrificing comfort.”
El Paso, Texas
is a close ratio 5th-gear replacement system containing significant
features and advantages not found in other designs. TwistGear fits 1991-up
Evolution and Twin Cam 88 5-speed transmissions, and older 5-speeds
back to 1985 with an appropriate conversion.
features include reduced transmission noise, computer enhanced ratios
(1st-4th), easier 5th-gear shifting, and significant improvement in
gearbox reliability due to major improvements in bearing and shaft design.
is straight forward, nearly identical to a fifth gear R&R, and
can be accomplished in the frame, and without modifying the case.
on whether or not primary or final pulleys or sprockets are swapped,
you'll either retain stock performance in 5th-gear combined with
acceleration gains in first through fourth, or stay with stock acceleration
curves while significantly reducing engine RPM in fifth for comfortable
cruising. Imagine...six speed performance in a five-speed gearbox,
without the expense, noise, or wear and tear of an overdrive! (Fifth
gear remains an
ideal 1:1 direct drive ratio.)
Helical Cut vs. Straight (Spur) Cut Gear Teeth
main reason helical cut gears haven't been used in American v-twins
is the cost to manufacture, but the benefits clearly outweigh the expense.
Not only do helical gears mesh more smoothly than spur gears, which
have no helix or twist to ease engagement, they also increase the contact
ratio. The result is superior tooth strength and reduced transmission
tooth strength is further enhanced by a high pressure angle and increased
gear width. The helical gear twist delivers a face contact ratio of
1.1, resulting in at least 1 tooth in contact at all times. The involute
gear profile gives a contact ratio of 1.4, resulting in at least 1 tooth
in contact at all times. Together, there are at least two gear teeth
in contact at all times.
Stock vs. High Performance Effect On Bearings
and moderate horsepower applications generate lateral movement of the
main gear inner drawn cup bearing, which will eventually work its way
out of the main drive gear with predictably disasterous consequences.
main gear replaces the use of this low-cost stamped shell needle bearing
with a high performance caged
roller bearing capable of much higher load and torque than either
OE or aftermarket bearings. Retained by snap rings on both sides, movement
in the bore is eliminated. In addition our caged bearing features 3.5
mm diameter heavy duty rollers, with three times the load bearing capacity
of standard 2.5 mm diameter needles.
transmissions use deep-groove ball bearings in the trapdoors, which
aren't always up to the task. Both stock and modified engines benefit
from Johnson Engineering's exclusive four-point
ball bearings in both trapdoor locations. The radial capacity of
the four-point ball bearing is double that of deep groove designs, while
the shoulder design allows for complete control of axial thrust.
Rugged One-Piece Countershaft Design
five-speed countershafts and gears are two separate pieces, resulting
in a skinny cross-section between the splines and teeth roots, and a
high stress concentration factor of 1.7 — not exactly the ideal
design for transferring gobs of big inch engine torque to a sticky rear
skin on a hot summer day at the strip and you're counting on riding
home with a nifty time slip.
unique one-piece fifth gear and countershaft, precision machined
from a solid
chunk of forged steel billet, has an ideal stress concentration factor
of 1.0 for superior fatigue resistance and built-in strength right
it's needed. The result is a gear and shaft so strong, we guarantee
it for an entire year against defects when used according to instructions!
Quicker Shifting, Lower RPM’s
a stock ratio 32/17 early style or 41/22 (1.88 or 1.86:1) 5th-gear
set with TwistGear's unique 41/20 (2.0:1) ratio
helical gears delivers 10% shorter 1st through 4th for a true close
ratio transmission. The result is better than six-speed performance
minus the fatigue of shifting, the expense
of a new transmission, and the noisey operation, coupled with
it's lower cruising RPM’s and improved gas mileage you're
looking for, a pulley/sprocket change is all that's required. In
short, you control the acceleration, comfort, and economy characteristics
TwistGear and your choice of transmission and/or wheel sprockets.
Easier Shifting Equals Better Performance
shifts result in faster acceleration and longer transmission life. Shifting
into 5th-gear is much smoother due to increased clearance on the main
drive gear dogs, which are back-cut for positive engagement. Porting
the dogs is no longer necessary for high-speed shifts.
are just a few of the highlights detailing the revolutionary TwistGear
close ratio helical transmission system. Get more
details on our expanded tech page and our How
Ratios Work page.
Also available in WideGear configuration
for fat tire conversions.
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.