Series IIa Land Rover Differentials
It has been said the Land Rover rear half shafts
are mechanical fuses to protect the differential...
Introduction
The Series Land Rover has two differentials, front
and rear, and the transfer box. In the coil-spring models, which have full
time four wheel drive, the straight transfer box is improved upon with either
a lockable or viscous coupling center differential .
When in a slight bit of trouble and you hear that
unmistable snap! from the
rear of the vehicle, and then forward motion ceases.
Note: clicking on one of the icons above will bring you to the
section describing it. Clicking on one of the illustrations below will show
a larger image of the same.
The Story
It was the last weekend in
May, and my friend Chris Vreeland was trying to replace the clutch on his
Chevy before attempting to haul all of his belongings from college and his
partially restored 1970 Cadillac Convertable back to the family home, part
way up the Maine coast. The engine was pulled and he thought he had all
the parts, but the throw-out bearing was either incorrect or in need of
replacement, and work stopped Saturday night because Chris had to get more
parts before the engine could be refitted to the Chevrolet.
Sunday, of the three day weekend,
and Chris has a reservation at the truck and trailer rental place to pick
up a two-ton trailer, by noon. This trailer is the largest
U-haul will rent, and it is the only one they have which is large
enough to carry the huge 1970 Cadillac Convertable. (It is enought to say
that three Mini Coopers could park in the same space as this Cadillac.)
Since the Chevy is obviously not going to be back under its own power by
noon, Chris persuades me to crank-over the 1969 Series IIa 88" in my
parents back yard and retrieve the trailer from the rental place in Albany.
We make the journey down to the place, hook up the trailer and start off
for the Student Auto Shop at RPI, (Chris' home away from home), and
make it to Troy without incident. At this point we are confronted with the
hill, and we've chosen the most direct approach up to RPI, which
starts at sixth street, has a STOP on the hill at eight street,
and then winds up through the campus onto the top of the hill, with a signal
at fifteenth street.
In choosing this route, one
thing is clear in our minds: we will run the STOP.
This bit of strategy only omitted
one thing, the idiot in the car behind us. Naturally a 2.25l petrol
engined Land Rover which is towing a trailer equal to its weight will not
exhibit the breath-taking acceleration of a modern rice burner. So we get
about one-third of the way up and this bozo behind us passes us and stops
at the STOP on eight street. It is about this point in time where I get
my first lesson in backing up a trailer, as at this point it becomes clear
to us that:
- The parking brake on the vehicle will not prevent the vehicle and trailer
from rolling backward on this slope, which at this point, seems darned
near to forty-five degrees.
- Since the parking brake isn't holding, and we're in two wheel drive,
any attempt to start off the hill will probably snap a half-shaft.
- We can't safely make it around the bozo at the STOP on eighth street.
So, we roll back down the slope and then try to re-start, at which point,
we hear the loud snaping noise, and all forward motion ceases. "That was a half-shaft",
says I. While I'm still holding the brakes, Chris hops out and locks the
front hubs. We roll back a bit further, from the gental slope to the flat,
and then start off again, this time in front wheel drive.
This well, and good, but it
does lead to some interesting moments, when the dips in the road and the
weight of the trailer tend to lift the front wheels off the road, and the
rubber up front chirps a wee bit. We top the hill and then head over to
the garage, where the trailer is detached and then we drive the Land Rover
into the garage, and heard some nasty clunking sounds in a brief attempt
to reverse. Given the recent events, I pull one half shaft. It is complete.
I go to the other side and pull the second half-shaft, it, also , is complete.
Uh-oh!
 Removal
The next step is to drain the
gear oil in the rear differential. As the gear lubricant flows into the
catch pan, there is the occasional plop-plop sound
as small chunks of metal find their way thgough the drain hole and into
the pan. Next the rear prop shaft is disconnected, and the rear differential
is removed, vith various bits falling on the floor.
The differential is shown at
right. This may not look so unusual, except that the hole (top right) in
which the shaft for the spider gears sits is not circular, but oval. Further
examination also shows that half of the gears show some amount of surface
pitting from rust.
 This would tend to indicate that this diff either
sat unused for a great period of time, or that it was half-filled with water
for a good period of time. It should be noted that when the vehicle was
purchased that the drive shaft had been put in out-of-phase, and the second
owner was reported to have used the vehicle to tow and launch his boat.
 Spider
With oval hole in the pumpkin,
it appears that the stres was then taken up by the spider gears and the
shaft upon which the spider gears were carried. The shaft and one of the
smaller gears were both split in half.
Repair
A quick trip to Rovers North
to purchase a used differential, and then I was back in Troy, and replaced
the diff with the assistance of a trolley jack and the rover was back on
the road with either rear wheel or four-wheel drive.
Bill Caloccia
Troy, NY
May 1991
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