Under carriage protection

**shamirj** · 20th March 2019, 10:43 AM

hi all,

Just curious whether some of these undercarriage protection is all that necessary on the D3. I am thinking of the D2 which really didn't have much protection underneath and the D3/4 have quite a few. I took my middle cover off to expose the sump to do an oil change and thinking do i really need to have one, and what am i protecting really? The last one is the transmission cover plate and again question the need for this one. If just touring don't see the need unless rock crawling. These covers made of steel are also quite heavy would prefer alum or lighter option or nothing at all. Also saves having to remove each time an oil change is required. And exposes the undercarriage for viewing for leaks better then it being all covered. Thoughts...

**twr7cx** · 20th March 2019, 10:50 AM

Depends what your doing with the car. I’ve left them off on our MY12 D4 TDV6 for the past fortnight as was finishing changing oils etc. The lady only uses it for her daily commutes and towing the horse float so I saw little risk.

I wouldn’t think your saving much in weight by not having them though. Plus it helps to just keep the underside clean - something I noticed with ours that above the plates was pretty clean for a 150,000km vehicle.

**hv_man** · 20th March 2019, 10:53 AM

Hi

I would leave them on or upgrade to an AL plate
For me better to be protected than have something damaged.

I highly recommend APT off-road
While also providing more protection they are also easier to clean out than the oem guards.

Compressor guard is the first item to buy if you have do so already

Followed by the front bash plate
Sliders are good protection, save me from expensive damage a number of times.
I’d then consider the transmission guard and then the sump guard last.
For general touring dirt roads etc the oem sump guard is adequate if off-roading this can be easy bent when pushing over rough terrain.

APT off-road Discovery 3 & 4

**101RRS** · 20th March 2019, 12:02 PM

I think the standard steel plate under the engine is pretty good as is (it is pretty thick) and I would only replace it with something heavier if dedicated rock crawling - mine has received a lot of hits but no damage.

The transmission cover is a different matter, it is not metal and if you got beached on a big rock in the middle it could very well brake through and damage the gearbox sump. Also while open to the elements with no protection at all the transfer case could be exposed to a large pointy rock that got past the rear gearbox X member.

If I were to get protection I would look (in priority order) at the gearbox/transfer case, the exhaust pipes under the rear suspension, the fuel tank, the air compressor and then the engine.

**BrianElloy** · 20th March 2019, 12:30 PM

I have the full suite of APT bash plates and rock sliders (front, sump, transmission, compressor, lower A-arms and rock sliders).

The first priority on a D3/4 is definitely the compressor bash plate, then transmission

Front plate is a good idea as are rock sliders if you plan on doing anything technical

All my bash plates have been .. um .. bashed.

They do add weight but they also lower the car’s center of gravity.

Bottom line is that they’re great insurance if you ever go out bush. Prevention is better than cure.

**loanrangie** · 20th March 2019, 04:16 PM

I agree that the standard under engine plate is quite good and there is a lot of space before it hits anything, replacing the plastic trans cover would be first on my list after the compressor.

**shamirj** · 21st March 2019, 12:20 PM

thanks to all replies.

seems like the engine one is not that necessary but will look at other options, something lighter like alum.
air comp cover doesn't have one, not needed. Its a coil sprung suspension

The gearbox cover yet to remove for the fuel filter but recall on previous D3 it was plastic from memory so will keep for now.

The other item i have removed was the plastic cover for the ABS, again nothing else there. seems like it doesn't really cover anything other then the ABS which again in the D2 days it was fully exposed no problems.

Tossing up for the battery cover, as there are some ecu's behind but i like to be able to see under the hood without having to take covers off. cheers

**Eric SDV6SE** · 21st March 2019, 03:05 PM

Originally Posted by shamirj

thanks to all replies.

seems like the engine one is not that necessary but will look at other options, something lighter like alum.
air comp cover doesn't have one, not needed. Its a coil sprung suspension

The gearbox cover yet to remove for the fuel filter but recall on previous D3 it was plastic from memory so will keep for now.

The other item i have removed was the plastic cover for the ABS, again nothing else there. seems like it doesn't really cover anything other then the ABS which again in the D2 days it was fully exposed no problems.

Tossing up for the battery cover, as there are some ecu's behind but i like to be able to see under the hood without having to take covers off. cheers

Under car covers are pretty important in my view, I've got an ARB bar, it's lower bash plates merge nicely with the factory engine plate. Transmission is still factory, and it's not full plastic either, appears to be some form of FRP or GRP.

APT compressor cover and transmission cover is still on the wish list.

All of my covers have got scratches, nicks, dents and marks on them, indicating that stuff does hit them. Id hate to think what kind of damage you would do if they weren't there.

Re Engine bay, covers are there for a reason. On top of the radiator and in between the top frame there's a foam rubber strip. Ours perished and this let's in all the road dust. The aero on the car draws in a lot of air over the engine via the grille to aid in cooling. If I didn't have the battery and brake systems covers on, everything would be covered in thick layers of dust.

I replaced the foam strip with the square profile foam you get from the green hardware store. No more high dust levels in the engine bay.

Plus I reckon the engine bay looks that much better with all the covers on.
20190316_113429.jpg

**fourteen8** · 3rd January 2025, 09:31 AM

Hi

Does anyone has this? Can it be installed with factory engine underbody protection? Thanks

Landrover Discovery 4 (2009-2015) Auto Xrox Transmission Guard Bash Pl
– Canyon Off-Road

**Slunnie** · 3rd January 2025, 03:53 PM

A lot of these factory plates underneath are about airflow. This is most definitely the case with the Disco5 (Cd 0.3), but even with the Disco3 they dropped the Cd from 0.41 to 0.40 with the D4. The D2 doesn't have them because it wasn't much of a consideration. Everybody looks at the flow over and around the vehicle, but under the vehicle isn't well considered and it also has a pretty significant effect on the aerodynamics - this has to be done now to reduce fuel consumption via flow and wake, noise and aero sensitivity from the spare tyre being mounted underneath the rear. Interestingly, from my extremely basic CFD type testing, spare tyre under the boot, or a long range tank or LPG tank in the same location has a massive ability to really mess up all of the airflow underneath the vehicle from underbonnet (radiator) airflow through to the wake - however a 4WD is quite high off the ground so its not so bad.

Just a moment...

2.2.2 Under-floor
A key challenge for the New Discovery (5) was developing an aerodynamic under -floor
with best in class off-road capability and robustness. An aerodynamically efficient
floor is usually achieved by maintaining as much longitudinal flow momentum as
possible as well as managing flow separations. The aerodynamic floor strategy is
presented in Figure 6.

D5-1.JPG

The engine and side under-trays were carried over from previous vehicles sharing this
architecture. The large aluminium transmission under-tray has been clad in a smooth
skin giving an incremental 3 drag count benefit and improving NVH performance. Its
trailing edge has been tuned to slight ly deflect the flow down to create a stable
recirculation bubble at the break-over x-location, thus maintaining flow momentum.
The flow re-attaches onto the exhaust SCR can at the vehicle centreline and onto the
urea and fuel tank cradles as illustrated in Figure 7 a). These protective shields have
been extended to maximise coverage and profiled to ensure minimal stagnation
pressure.

D5-2.jpg

The large radius used on the lower trailing edge of the fuel tank cradle to avoid
grounding was initially adverse for drag, causing the flow to turn upwards in an
unsteady manner. Deflectors have been developed to guide the flow more efficiently
and preventing it from impinging on the sub-frame and suspension arms. This resulted
in a drag reduction of 2 counts.

The heat shield surrounding the spare wheel was optimised to give the required
thermal protection without a drag penalty. For powertrains with a single sided exhaust
muffler, an in-fill tray was engineered to bridge the void between the suspension and
rear bumper.

Eventually, the development of a low-drag wake was achieved by forcing the flow to
separate steadily over time along the y-axis, at the same x-location. At the vehicle
centreline, the heat -shield z-location was optimised to ensure separation at this
location, thus enabling the drag to be insensitive to the presence of the underslung
spare wheel, or its size. Outboard of the centreline, the rear suspension arm trailing
edge was used to force separation as illustrated in Figure 7 b).

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