PHASE 4: Differentials, ARB lockers and more
So we've got a 300 Tdi and a nice lift kit nearly done in the Discotech and all is coming along nicely, but along with such a great engine with all that low end torque we've got to think about the big picture. The big picture meaning the entire vehicle, from lug nuts to engine. Sure you can install the ECR ROX wheel flares and stick 35s under your Disco, but you have to think about what that will do to the rest of the drivetrain. Think about the added stress and strain on your CV joints, center diff. and axles. The entire package has to be set up to be trouble free for the long term.
Can a Rover be set up to run 35" tires with bulletproof reliability?? Sure can. Any Disco, Range Rover Classic or Defender can, but it means a lot of changes have to be made. For example, we run 35x12.50x16 tires on our Defender project, ECR 4. The rear axle was upgraded to a Safari Gard 30 spline unit and the front axle was upgraded to HD 24 spline inners with 1 ton CV joints and thick drive flanges. That vehicle has done dozens of trails in new England, from the HEC (Hope Expedition Center) to Eagle's Ledge and trails in Moab from Hell's Revenge to Pritchett Canyon (with all the side obstacles), and it is driven every day as a commuter and it drives to all the events, even across country. With all that use and abuse and over 40,000 miles the project has never had a failure on the road or on the trail. The point is, as long as you look at the big picture and don't try to run 35s on your stock CV joints, you'll be all set, and bulletproof.
The first step in our axle and gearing work for the Discotech is to swap out the standard "open" diffs and install ARB Air Lockers front and rear. Along with the lockers we'll be adding a set of 4.11 ring and pinions. We went with the 4.11s for a number of reasons:
#1. The will give us the correct gear ratio for us to utilize the power band of the 300 Tdi
#2 They will give us a better low range crawl ratio
#3 They will help compensate for the larger tires we will be installing
We opted for the ARB air lockers for a wide variety of reasons. The locker debate is one that puts people into a frenzy, so we'll list our reasons, but we also strongly agree that out of the many types of lockers out on the market, all of them work well for different reasons and there is no right or wrong answer on lockers. It comes down to what is right for you, your truck, your budget, etc.
Our reasons for going with ARBs are:
#1 Selectability. This is of major importance to us here in snow and ice country. We just don't like the way automatic lockers work on snow and ice when you drive hard like we do. Being able to "unlock" also helps to limit stress on axle parts as you only really stress the axles while "locked" and with a selectable locker you aren't "locked" when you go pick up the kids at school, only when you hit the button on the trail. This also saves slightly on tire wear.
#2 Strength. When set up properly these units last a long time. We've had Rovers with over 100,000 miles with ARB lockers installed and no failures. The only failures we have had are with customers that let their axle breathers plug up and that can cause an O-ring failure, but with proper care they last indefinitely.
So our choice is .
In the image above you can see that we have pulled the rear differential
and have it out on the bench. The next step it to remove the stock 3.54
ring and pinions and the stock center section. While we are into the diffs
we'll install new bearings and pinion seals as well, just so that we won't
have any differentail issues for the long term.
Here you can see the diff built up with the RD56 ARB 24 spline locker and
the Ashcroft 4.11 ring and pinion. You can also see that the 4.11 ring
gear requires no spacers or shimming to fit the 24 spline set up. It is
made to correctly bolt in and last for a long time. The green arrow points
to an ECR trick that we developed from doing so many ARB air lockers. In
the instructions they want you to drill a hole in the casing and use a
compression fitting to come out of the diff. with the air line. We no longer
install them that way and have come up with a better ECR way. The way the
instructions tell you to do it works well, but does not take into account
potential field fix issues. If, for some reason, you had to remove the
air line with the through the casing air fitting it can loosen up. This
would mean that you would need to remove the entire differential from the
axle tube and re-tighten the fitting. That is a long job for just a loose
fitting, and that just isn't acceptable here at ECR. Nobody wants to do
that job on the trail. So to solve the issue we drill through the top of
the diff case and thread the entire hole. We then fit a compression fitting
inside the diff. case. Next we install a 90 degree fitting on the top of
the diff. This does a number of things.
#1. It makes it so that if you need to replaced or re-route your air line
you will have no chance of loosening the internal fitting and causing an
air leak because the two fittings are independent of each other. Loosening
or removing one in no way relates to the other.
#2. It routes the air line directly down the axle tube and therefore the
air line does not stick up, so there is less chance of pulling off an air
line when driving in heavy debris, or getting it melted on the V8 exhaust
system.
The removal of our ABS pump made for a tidy spot to install the ARB air
compressor and associated solenoids. The unit is tucked nicely under the
hood, easy to service and mounted on rubber isolators so that it operates
quietly.
Interior controls for the ARB lockers fit nicely in this little overhead
space on the Disco. This makes for ease of use and utilizes a space that
was blank in our Disco.
The addition of the ARB lockers will transform the Discotech from "average"
off road into an "amazing" off road rig. It is truly astounding
what actual 4 WHEEL DRIVE will do for you!
On to the next phase of the project.
Special thanks to Air Locker Inc.
for the ARB products!
If you have any special requests or questions about anything on your Disco
or our Discotech project, feel free to email.
We'll be more than happy to help.
PHASE 1: Paint and Body
PHASE 2: 300 Tdi and 5 speed install (also
includes bumpers, etc)
PHASE 3: Stage II Suspension,
wheels and tires
PHASE 5: Seat covers, roof rack
and the rest