|
|
|
|
Removing a Front Wheel Knuckle
by Egon H. Elssner
General
After several cycles of knuckle removal and installation I
have settled into the detailed procedure that follows. The procedure
does not require the use of a high power impact wrench which makes
it useful "on the road."
The procedure and data given here are based on the X7525A
GMC Motorhome Maintenance Manual and presentations given originally
by Darrel Winterfelt, Ken Thoma and others. As with all non-GMC
approved procedure, what you do to your coach, you do it at your
own risk.
Knuckle Removal
In the process of removing the knuckle, a lot of torque is
usually needed to loosen up the drive axle nut. First, the transmission
should be taken out of Park because the parking pawl inside the
transmission may break during axle nut loosening.
I have found that the necessary torque to loosen the axle
nut may be applied if the wheel is left on the vehicle and the
tire is on the ground with the normal weight on it. The rear wheel
parking brake will usually not be sufficient to hold the vehicle
during this loosening
procedure. I have found that an easy and safe way to hold the
coach is to
simply drop the two rear support bogies onto suitable wood blocks
by letting the air out of the air bags.
Loosening the drive axle nut will require a high torque wrench
setup. A very satisfactory arrangement can be made up by using
a long handle wrench. For some stubborn axle nuts it may be necessary
to apply torque of up to 1000 ft. lbs. This is equivalent to a
160 lb. man standing on the end of a 6 foot long wrench! To make
up a long wrench, I start with a 3/4 inch drive breaker bar (about
20" long) and make extensions out of pipe.
Pry the grease cap from the front wheel. Remove the drive
axle nut cotter pin and place a 1 1/2 "socket with a 7"
extension over the nut. The extension is necessary to get the
handle of the "breaker bar wrench assembly' away from the
side of the coach. With the extension it is necessary to support
the breaker bar
end of the extension to be able to use the breaker bar. For this
support I use a
piece of 3/4 inch plywood, standing on edge, with a suitable hole
(1 1/2" dia. for the head end of the extension) drilled at
the correct height. Loosen the drive axle nut but do not remove.
Loosen the wheel lug nuts but don't remove. Place a 4 ton
bottle jack under the frame to the front frame extension junction
and raise until a 12" high jack stand fits under the frame
alongside the bottle jack. Remove the bottle jack and place it
under the lower control arm just outboard of the sway bar. A small
iron plate or bar can be used between the jack and the control
arm to distribute the load to both sides of the control arm. Raise
the wheel off the ground just enough to remove the wheel. Remove
the wheel.
With a suitable two-jaw puller remove the steering tie rod
after removing the cotter pin and nut. Removing the steering tie
rod at this time allows the knuckle to be moved from side to side,
useful in removing the brake caliper. Move the tie rod out of
the way.
Using a 3/4" box end wrench with a long handle, remove
the upper ball joint nut after removing the cotter pin. No need
to worry about the upper ball joint stud coming loose, it will
stay put until removed from its tapered socket at a later time.
After removing the nut remove the brake line clamp from the ball
joint stud.
Obtain a piece of wire to support the caliper when removed.
With a 3/8" hex wrench (Allen), back out the brake caliper
bolts. Remove the brake caliper assembly and support it from the
upper end of the shock absorber with the wire, being careful not
to kink the brake line or to drop the brake pads out of the calipers.
Make sure that the drive axle nut can be easily removed at
this point, but leave the nut on until ready to remove the knuckle.
The GMC Maintenance manual shows the lower ball joint being
removed with a large two jaw puller. Some mechanics loosen the
lower ball joint by supporting the end of the lower ball joint
stud (on the backed off nut) on a small jack to apply a pop out
force and, with a pair of hammers, beat on the flange until the
cone of the ball joint pops out. A far easier solution is to use
a two jaw puller made of a modified Pitman arm puller. A few turns
with a long handle wrench separates the ball joint from the knuckle.
The next step is to loosen the upper ball joint. The classic
way is to apply pressure with a crow bar between the knuckle and
the upper control arm and, using a hammer backed up by another
hammer on the opposite side, rapping the flange holding the ball
joint stud until it yields. A much easier and less damaging procedure
is to push the stud up using a 'pusher'. The pusher is inserted
behind the joint (over the CV joint). The upper part of the pusher
fits over the knuckle flange (around the grease boot) and the
ball joint stud fits into the slot of the lower bar of the pusher.
After taking up the slack and aligning the pusher into position,
a few twists of a short handle open-end wrench pops out the stud.
It's a good idea to put the stud nut back onto the loosen ball
joint until the knuckle is ready to be removed.
Everything is now loose, ready for knuckle removal. Remove
the nut on the lower control arm. Remove the axle drive nut and
washer and push the drive axle back as far as it can go (into
the inner CV joint). While holding the knuckle to stabilize it,
remove the upper ball joint nut and swing the upper control arm
up and out of the way. An important procedure follows: Tilt the
knuckle top outward and turn the knuckle (to the fight or left)
to gain sufficient clearance for the drive axle to come out of
the hub and the lower ball joint stud to come free of the knuckle
simultaneously. The knuckle is moderately heavy (about 50 lbs.)
and with the drive line still attached, even slightly heavier,
so caution is advised in handling. Lower the knuckle to the ground.
Reassembly
Replace or repack wheel bearings and replace upper and/or
lower ball joints as needed. Clean the ball joint cones and cone
bores of the knuckle. Only a slight trace of grease is permitted
for assembly (See the X7525A manual, Page 3A-22 (Note)). Lightly
grease the seal area of the CV Joint.
Pre-position the drive axle end and lower ball joint to maximize
working space when lifting knuckle into position (see Disassembly).
A rubber band wrapped in a figure 8 around the lower ball joint
grease boot and the lower control arm will help hold the boot
in place during assembly.
Lift and position knuckle to engage drive axle and lower ball
joint stud. Start lower ball joint nut on stud. Having an assistant
handy helps while lifting the knuckle into position and starting
the lower ball joint nut. An alternative is to balance the knuckle
on a block of wood or small jack. Fully engage drive axle into
hub, place axle nut washer and start drive axle nut. Run up the
nut on the lower ball joint nut but do not torque. Pull down upper
control arm to engage ball joint stud and start nut (without brake
line clamp at this time).
Lightly tighten the drive axle nut. Visually make sure that
the outer CV Joint mates with the drive axle seal. Any gap between
the joint and seal will result in grease leakage, bearing contamination
with dirt and water with possible bearing failure and brake pad
and rotor contamination by grease.
Torque the lower ball joint nut to 100 ft. lbs. Check alignment
of cotter pin hole and tighten nut to insert the cotter pin. If
the torque seems excessive, try a different nut. Fit the cotter
pin.
Torque upper ball joint nut {without the brake line clamp).
Without a special adapter which I haven't been able to find, it
is impossible to accurately torque this nut to the specified 40
to 60 ft. lbs. Use a long handle box end wrench to set the cone
of the ball joint stud into the knuckle, estimating the applied
torque as best you can.
Clean and grease (with a silicon grease) the bushings upon
which the caliper slides as the pads wear. See the X7525 manual,
Page 5-20 Figure 12.
Check the lay of the brake hose and slip the brake caliper
into the knuckle. Very likely you will need more pad to pad clearance
to do this easily. Push the brake cylinder into the caliper with
either a tool made for it or a C clamp and suitable metal plate.
It may be necessary to drain some brake fluid from the master
brake cylinder to avoid overflow when pressing the cylinder into
the caliper. See the X7525 manual, Page 5-19.
Insert the caliper bolts and torque to 35 ft. lbs. It is important
to torque these bolts because they can work loose and cause catastrophic
braking/drivability problems if they fall out (a personal experience)
With the brake pads relatively loose, check that the caliper assembly
slides freely on the bushings.
Loosen and remove the upper control arm stud nut. Place the
brake line clamp over the stud and replace the nut. Check the
brake line for freedom of movement when the knuckle is moved from
side to side. Tighten the nut to insert the cotter pin. Fit the
pin. At this time, it's a good idea to degrease the brake rotor
with a spray brake cleaner and clean paper towels.
From inside the coach, step on the brake pedal to set the
brake caliper. Check brake fluid level. Most likely, the brake
pads will drag after this operation. The pads are normally pushed
apart by the slight typical side to side wobble of the brake rotor.
It is, however, a good idea to check for brake drag and heating
.after a few miles of driving.
Fit the steering tie rod and torque the nut to 40 ft. lbs.
Tighten nut to allow cotter pin insertion. Fit the pin.
Before you install the wheel, tighten the drive axle nut as
much as you easily can (up to about 140 ft. lbs.).
Install the wheel and tighten the lug nuts as much as you
easily can. Block the wheel with a 2x4 and torque the drive axle
nut to 140 ft. lbs. Torque the wheel lug nuts to your favorite
torque (I use 200 ft. lbs. on my steel rims, the owner's manual
says 250 ft. lbs.). Lower the wheel and remove the bottle jack.
Place it under the frame and remove the frame block.
Check the fit for a cotter pin on the drive axle. Tighten
(but never loosen) the nut to the next pin insertion point. If
the torque would appear to greatly exceed 280 ft. lbs. (the upper
end of the 140 to 280 ft. lbs. specified in X7525) it might be
a good idea to try a different axle nut or washer. Fit the pin.
A slightly curved pin goes in quite easily. With a screwdriver,
bend up the longer end of the pin leaving the shorter end straight.
Tools and Props in approximate order of usage
2 wood blocks 12" long 6 x 10 (for rear axle support)
Small chisel or screwdriver (for cap removal)
3/4" drive breaker bar
7" long 3/4" drive extension
1 1/2" socket, 3/4" drive (for drive axle nut)
6 foot extension for breaker bar
Piece of 3/4" plywood with hole (for breaker bar support)
Bottle jack, 4 ton
12" high Jack Stand or wood block equivalent
Small metal plate or bar {for lower control arm jack support)
heavy duty wire cutter for cotter pins {8" handle is nice)
pliers or long nose pliers (for cotter pins)
3/4" socket, 1/2" drive (for steering tie rod nut)
3/4" box end wrench, long handle {for upper ball joint nut)
3/8" hex (Allen) wrench with 3/8" drive (for caliper
bolts)
6" long 3/8" drive extension
1/2" drive to 3/8" drive adapter (to adapt torque wrench
for caliper bolts)
12" piece of 1/2" or 3/4" pipe to extend ratchet
wrenches (for convenience) Upper ball joint pusher
15/16" socket, 1/2" drive (for lower ball joint nut)
Lower ball joint pusher
3/8" drive ratchet wrench
1/2" drive ratchet wrench
1/2" drive torque wrench, to 150 ft. lbs. (for steering tie
rod, lower ball joint nut and brake caliper bolts)
3/4" drive torque wrench, to 300 ft. lbs. (for drive axle
nut and wheel lug nuts)
Socket for wheel lug nuts
Cotter pins: 5/32" x 1" (for axle drive nut}, 1/8"
x 1 1/2" (all others).
We Have A Website!
For parts and service repair listings and more, check it out
at: www.gmcws.org The site now has an on-line membership application
and links to other GMC Motorhome related sites. Please pass along
any information you would like published as well as suggestions
for improvement to Tony Weir at tweir@pacbell.net.
|
|
|