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of The Green Rover
Drive train rebuild of Summer, 2007,
or how a change can have
unintended consequences
Did you ever have a project you did to improve things come back
to bit you in the trail? Or guess wrong but end up doing
the right thing for the wrong reason? I have.
Back in 1996, with the help of a friend I converted my 109 from
a Rover Rear axle to a Salisbury (Dana 60 built by Land Rover under
license). The salisbury is a big beastie that is both longer
and sits lower than the Land Rover rear axle. But the axles
are a lot stronger and I had recently broken my sixth rear 10 spline
Land Rover axle. Salisbury's are standard fitment to Series
III 109s so a stock Series III rear propshaft is just the right
length for fitting between the transfer case and the longer salisbury. To
compensate for the increased depth of the Salisbury I fitted military
109 long shackles and taller tyres. Everything was bolt on
and worked fine. What I forgot to note is the the increase
in ride height meant the transfer case and differential sat slightly
farther apart so that at rest both the front and rear propshaft
slip joints were a little more extended than stock.
In 1998 I replaced my leaf springs. Before they went on I
rebuilt the rear set with UHMW (ultra-high molecular weight) Polyethylene
plastic sheets between each leaf. This plastic provides a
low friction surface, similar to Teflon tape, but with a much higher
abrasion and puncture resistance. The goal was to eliminate
leaf to leaf friction so that the springs were freer to move with
the terrain. This worked quite well softening the ride and allowing
for greater spring articulation. Since everything was apart
I went ahead and replaced the poor condition stock frame bushings
and new spring bushings with poly bushings. Poly bushings allow
the shackles to move more freely and respond better to spring movements. I
didn't have enough plastic to convert the front springs so decided
to postpone the front spring plastic upgrade.
One thing I didn't know at the time is that Series Land Rovers
use a short prop shaft slip joint. The stock suspension
doesn't articulate well so longer slip joints are not needed and
who knows, maybe the factory saved a a little money by specifying
a short slip joint. Or maybe some factory engineer ran the
numbers and decided that was the length needed for a stock Series
Land rover. I didn't think about slip joint travel length
when I modified my springs to articulate better and wouldn't be
surprised if people who convert to parabolic springs don't think
about it either. This might be a problem only when
both wheels on an axle are at or near full lower articulation at
the same time. Not a condition Land Rovers driven on the street
or on mild trails encounter.
In 1999 Timm Cooper converted my Land Rover to a V8. The
transfercase stayed in the same front to rear location but moved
to the right to allow the engine to be centered within the frame.
The engine mounts were raised a little to allow the Ford oil pan
more clearance over the front differential. The transfer
case mounts stayed in the stock vertical location. This
slightly decreased the angles on the rear prop shaft and increased
the angle on the front, slightly increasing the distance between
the front prop shaft mounting flanges. Timm decided that a slightly
longer front propshaft was needed to re-center the slip joint travel.
We took my front prop shaft to a specialist along with the static
distance between the mounting flanges for a slip joint replacement.
At that time I specified that the next longer slip joint be used. Since
the rear prop shaft fitted OK, and was only 3 years old no one
gave a thought to how far the slip joint was extended.
I soon noticed a clicking sound from the front when I was off
roading in 4WD. I traced the click to the front U joints
binding and took a die grinder to them to increase clearances.
I should have ordered higher angle yolks as well as a longer slip
joint. on the front prop shaft.
During 2001 I finally got around to rebuilding the front leaf
springs with UHMW plastic sheets so the front springs would have
increased articulation. I also had taller 33.4" diameter tyres
installed. I noticed that the larger diameter tyres cleaned
off the dirt on the back of my built in water tank during my more
technical off road excursions. The water tank sits in front of
the left rear wheel. For some unknown reason, Land
Rover mounted the axle an inch and a half forward of the centre
of the body rear wheel arch. I decided to solve the rubbing
problem by moving the rear axle assembly rearwards 1-1/2 inches. It
centres the wheel in the wheel arch providing additional clearance
and decreases rear body overhang. I accomplished this by
using a locating pin offset plate between the leaf springs and
the axle housing. The spring pack has a locating pin and
the axle housing has a hole for the pin. This keeps the axle
assembly from moving about on the springs. An offset plate
has a hole for the leaf spring pin and a pin located elsewhere
for the axle housing. I installed the plates one at
a time by removing the U bolts, rising the body slightly, installing
the offset plate, rolling the axle housing back a little, lowering
the body and reinstalling the U bolts. I didn't need to
remove the rear propshaft to accomplish this.
I had extended the distance between the rear prop shaft mounting
flanges when I installed longer shackles then again when I moved
the rear axle assembly 1-1/2 inches to the rear. I just forgot
to account for how any change can adversely affect other things. Slip
joints make prop shafts adjustable length items, right? I
forgot the Land Rover slip joint was short. In reality I
have used up virtually all the rear prop shaft's slip joint extension
with the vehicle sitting static.
During 2002 I was climbing in loose rock, loosing traction and
the vehicle started bouncing up and down on the springs. The
nut holding the prop shaft flange to the pinion gear stripped off
leaving my front propshaft end on the ground. After
I got home I tried a simple fix by replacing the stripped pinion
nut. When I tried to drive in four wheel drive I quickly discovered
that the front ring gear had a couple
broken teeth . I replaced the ring & pinion gears. I
also noticed a shiny ring around the front prop shaft just below
the edge of the bellhousing. The increased front articulation
from eliminating leaf to leaf friction allowed the front propshaft
to strike the bellhousing at full downward articulation and possibly
exceeded the prop shaft slip joint movement at full lower articulation
when the vehicle was bouncing on the springs. I decided to
address the body hopping on the springs in a future shock upgrade
and meanwhile try not to get into a situation where the body
bounces causing the springs to flex between full upward and full
downward articulation. A future shock upgrade would include
moving the shock mounts farther apart and installing stiffer,
longer shocks. Possibly dual shocks since the sprung weight
is high.
When the ring and pinion was replaced, I discovered a twisted
front axle that was close to breaking and replaced it. . I
had broken a front axle previously in 1998 while off roading on
the Border to Border marathon run between Canada and Mexico. So
this was front axle #2. I
decided to put 24 spline front axles on my future upgrade list. This
upgrade was stalled because of the high cost of 24 spline front
axles. I just stopped driving the more technical trails until I
could get the shocks upgraded and figure how to handle the front
prop shaft issues.
In 2005 I found myself on a loose dirt downhill slope and needed
to back up. The vehicle started to bounce on the springs
again. I minimized the bounce as much as I could to get out
but noticed a new sound in four wheel drive. I concluded
that I had damaged the front ring and pinion gears again, put the
vehicle into 2 wheel drive and unlocked the front hubs. I
decided to just drive in two wheel drive until I could afford
a diff and 24 spline upgrade. This of course kept me off
everything except pavement and well maintained trails. This
turns out to have been a good move, but for the wrong reason.
During the summer of 2007 I was given an almost new pair of used
SeriesTrek 24
spline front axles making my front end upgrade affordable. I
commissioned
Great Basin Rovers to build me a differential
with a 24 spline Trutrac carrier and stronger than stock 4.75:1
ring and pinion gears. I
also ordered a custom front prop shaft that had a smaller diameter
shaft where it passes by the bell housing, longer slip joint and
high angle U joints. Linus Tremain came by to help and do
the heavy lifting in getting one diff out and the other in. While
dropping the front prop shaft he noticed that the transfercase
was free to wiggle when the front prop shaft was wiggled. We
also found that the front ring and pinion gears were in good shape
and not damaged as I had believed. Instead the transfer case had
come loose from the gearbox! Or more precisely the adapter
plate that goes between the Borg Warner T-18 gearbox and the Series
Land Rover transfer case came loose. In four wheel drive
the loose transfer case was causing symptoms that were like the
ones I had with broken front ring and pinion gears.
With the front axle
upgrade completed the project moved to the middle of the vehicle
and I removed the transfer case to find out why the adapter plate
was loose on the gearbox. As it turns out, all four mounting
bolts had worked themselves back out. I also discovered that
the movement had destroyed the rear output shaft bearing, the thrust
washers against which the bearing rested and damaged the rear of
the main output shaft. I wasn't sure why the mounting bolts
backed out. The hardened allan head bolts and the threads
in the gearbox were fine. I bolted the adapter back in using
loctite and likely more torque. Before
I used an 'L' shaped allan wrench to tighten them down. This
time I bought an allan head socket and used a socket wrench for
additional torque. I
had a hard steel sleeve made up to repair the main output shaft
where it rides against the rear bearing and replaced the
rear bearing. When
I went to replace the transfercase intermediate gear I discovered
a damaged thrust washer and replaced it. I also went ahead
and replaced a worn emergency brake expander unit, the rear output
oil seal and number of BSF nuts that got rounded off from
using the wrong size wrenches. Of course I assumed
everything was in good reusable condition and the project got
stopped each time I discovered an out of spec part. I really
should have inspected everything before I started reassembly. It
would have saved me a lot of time.
Font end rebuilt, transfer case and adapter reassembled, new improved
front prop shaft installed, all I needed to do was install the
rear propshaft and ...
The rear prop shaft barely reached the rear diff at full extension. Whenever
rear downward articulation occurred the rear propshaft would pull
on the transfer case with the force generated by several hundred
pounds of moving salisbury axle assembly and those big 33.3 inch
dia tyres. No wonder the adapter plate bolts worked themselves
loose. What I thought was a damaged front ring and pinion
gear ended up being a too short rear propshaft pulling on everything! All
because I didn't think to measure the flange to flange distance
when I did something to affect it. And I've known since 1999
that Land rover slip joints are short. It just didn't occur
to me that I had run out of slip joint movement with the vehicle
stationary. I
ordered an new custom rear prop shaft from Great
Basin Rovers.
This one the correct length got my rear flange to flange distance
AND with a long slip joint.
The lesson in this story is that any change made to your vehicle
affects other parts of the vehicle, often in unanticipated negative
ways. It is important to think beyond the immediate scope
of a project and try
to understand how a change will affect each related part. Increased
articulation affects propshaft clearances, puts addition strain
on shocks and increased extension of the propshaft slip joint. Something
that would be good for people converting to Parabolic springs to
think about. Moving
prop shaft mounting flanges farther apart reduces the amount a
prop shaft slip joint can expand before the diff and transfer case
are pulling against one another.
Of well, when all was said and done I did end up with a new 24
spline front axle conversion, correct length front and rear propshafts
and a resealed partially rebuilt transfercase. But I
could have avoided 2/3rds the work and 3/4 the time if I had just
remembered that moving the rear axle affects propshaft length years
earlier.
Mid 2009 addendum: Both the new propshafts that Great Basin Rovers sold me have twisted and need replacing 2 years from new. I had Rover propshafts behind my 302 for the previous 7 years without any twisting. And no, I have not done anything during the last 2 years that I hadn't been doing all along. In fact 2009 has seen only one trip because of a lack of funds for fuel.
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