Originally Posted by
mnpracing
UNIQUE FUNCTIONAL PRODUCTS
SERVICE BULLETIN
Subject: Replacement of torsion axle.
Application: Torsion axle trailers.
Condition: Rubber suspension element failure allowing trailer tire to contact
fender.
Tools Required: Air wrench; torque wrench; ¾” socket (for lug nuts); 15/16”
socket and wrench (for axle trailing arm and axle mounting bolts); 3/8” flair
wrench (for brake lines); floor jack; jack stands.
If any trailer tire has significantly less fender clearance when compared to the
other trailer tire(s), axle will have to be replaced.
To Remove Axle:
Step 1: Jack up trailer and set on jack stands such that the tires and wheels and
the defective trailer axle can be removed.
Step 2: Remove tires and wheels, setting aside the lug nuts, which will be reused.
Step 3: Remove 5/8” bolt and nut from each axle trailing arm using the 15/16”
socket and wrench. The bolt must be completely removed. Slide the trailing arm
off of the splined axle shaft. (Note: If the trailing arm is hard to remove, insert a
wedge, such as a screwdriver, into the slot of the trailing arm to spread it open
for easier removal).
Step 4: Carefully hang the trailing arm from the trailer frame using a wire tie or
rope. Be careful to not stress the brake line or brake hose.
Step 5: Remove the (4) 5/8” bolts and nuts that attach the axle to the trailer frame
using the 15/16” socket and wrench. Slide axle down to clear trailer frame
brackets and remove.
To Replace Axle:
Step 1: Install axle and bolt into the trailer frame brackets. (Note: The axle
mounting bracket is not centered over the square axle tube. The long part of the
mounting bracket should be facing toward the rear of the trailer). Torque the (4)
5/8” bolts and nuts to 150 ft.-lbs.
Step 2: On BoatMate ski boat trailers, there are only two trailing arm positions
used. The only axle that is set to 24 (+/- 2) degrees below horizontal will be a
single axle that has a 15” wheel and five lugs. All other single axles (14” 5-lug
and 15” 6-lug) and all tandem axles are set to 18 (+/-2) degrees below horizontal.
Each spline on the shaft moves the trailing arm angle by 6 degrees. If an angle
finder is available, make certain the top of the axle tube is level and position the
trailing arm to the correct angle as shown in photo.
On BoatMate runabout trailers, there is only one trailing arm position regardless
of axle. This angle is 30 (+/-2) degrees below horizontal. Again, each spline on
the shaft moves the trailing arm angle by 6 degrees.
If angle finder is not available, position trailing arm horizontally then move down
the correct number of splines. Move three splines for the 18 degree setting, four
splines for the 24 degree setting and 5 splines for the 30 degree setting..
Slide the trailing arm onto the shaft. . (Note: If you are having trouble installing
the trailing arm, insert a wedge, such as a screwdriver, into the slot of the trailing
arm to spread it open for easier installation). Bolt the trailing arms to the splined
shafts using the 5/8”x 3-1/2” long bolt, washer and nylock nut. Torque bolts and
nuts to 150 ft.-lbs.
Step 3: (For brake axle only) Re-attach brake lines and bleed trailer brakes. This
may not be necessary if the instructions from step for in the Removal section
have been followed.
Step 4: Re-install wheels and tires. (Note: If equipped, care should be taken not
to damage the wheel plastic hub insert). Hand torque lug nuts to 95 ft.-lbs. using
the every other bolt method.