Hilux Diff Drop
Over the years, a number of different diff drop kits have been developed for the Toyota Hilux. Lets have a look at some.
The 1" spacer style Diff Drop
This is to explain to anyone what the 1" diff drop spacers are and what they do. There are alot of rumours/falacies when it comes to using these spacers and I hope to clear up some confusion regarding the topic. The 1" diff drop spacer are exactly that - spacer that are 1" in height that fit between the front two differential mounts and the crossmember tha mounts bolt onto. This here is a pic of what the kit looks like -
Here's what they look like when fitted to to a 2005 and on Hilux.
Now there are for's and against's with this kit. Some Suspension kit's offer them included but a quick Google search will find numerous suppliers of this style of diff drop kit. These kits are advertised as lowering your front diff one inch so as to reduce the CV angle on your driveshafts due to installing a suspension lift. This is misleading and doesn't go into full details about the true results of installing this. Let me explain. Does it reduce cv angle? Yes it does, but no where near the 1" that is claimed by the distributors of this type of diff drop kit. You will only get half an inch reprieve at most due to the "cantilever effect" that the front diff has and its position in relation to the Driveshafts. here is a great diagram to explain what I mean -
The 1" diff drop kit does drop the front mounts an inch, but because of the position of the CV shaft it doesn't lower the diff by 1" due to the rear mount still being fixed above the rear crossmember. A quick CAD sketch using the dimensions above shows that the actual diff drop achieved is only 9.53mm so that is all of a reduction in CV angle achieved. with this type of kit which is hardly worth bothering with. Who in their right mind would give up 25mm of clearance to gain a CV reduction of just 9.5mm? Surely, you would be better off lowering the suspension lift by 9.5mm which would give you 16mm more clearance overall.
The Arm or Cradle style Diff Drop
The next iteration of diff drops that proved quite popular for sevearal years was the cradle or arm style diff drop.
This style replaces the diff mounts and allows the diff to be relocated by around 30mm. This design has a weakness because of the single ended mount shown on the left side of the photo above. The factory bash plate cannot be refitted after this style of diff drop is fitted and requires fitment of a bash plate with a hump protruding below the bash plate to protect the lowered diff. Some designs of diff drop bash plates are quite chunky and leave your rig exposed to getting hung up. Look for a nice tapered design with a minimal diff hump for best offroad performance.
In recent times, this design has fallen out of favour becasue it has been prone to bending of one of the mounting arms in off road conditions.
Double mounted Cradle style Diff Drop
To compensate for the weaknesses of the single ended arm stylemounting system several suppliers have recently developed a double ended mounting system as shown below. The one shown here has been machined out of billet steel which adds to cost and weight. This also drops the diff by about 30mm. Unfortunately, a complex mounting system and billet steel design adds significantly to weight, about double its competitors.
The next iteration of this style of diff drop was made from folded steel. This design has a couple of weaknesses. The first is lack of strengthening gussets on the arm in th ebackground.
The other weakness is not so obvious but it relates to the fact that the diff drop contains a bend that is too acute to be able to be done on a brake press and a butt weld is used. Lets have a look at it close up.
You can see that two parts are offset from each other to allow the fabricator to apply a fillet weld on each side. This causes two problems. First, the thickness of the load bearing steel is significantly reduced and the weld itself is a weak point due to the amount of penetratin that can be achieved when fabricated. We have received reports that this type of diff drop has been known to fail offroad either from bending or breaking at the weld.
The latest diff drop design and in our view the best solution out there is the one from Buds Customs. In our view its by far the best engineered solution seen to date as its been designed and manufactured by offroaders for offroaders.
Whilst still a fabricated solution, by use of meticulous attention do detail to the design which includes low profile custom Australian made urethane bushes and countersunk bolts, This kit achieves the highest diff drop in its class at 35mm. Weaknesses from butt welds has been avoided by using advanced manufacturing methods allowing the full thickness of the steel to be retained. So in summary, this diff drop avoids previous weaknesses and features:
- Low profile slim line design
- Industry leading 35 mm diff drop (37 mm measured on prototype)
- Best clearance by far.
Some misinformed people have stated publically that the extended diff drop will lead to problems on uptravel and the CV might possibly disengage on uptravel. VMN has tested this and found that when fitted to a N80. With the bumpstops removed, the UCA hit the body on uptravel 215mm above ride height. Even at this acute angle., the CV was not binding and the wheel hub could be turned by hand. However, with a trye fitted, there are a number of other limits that prevent this extreme CV angle.
- Travel of the shock (measured 50mm at ride height)
- Bump stop limiting travel (measured 40mm at ride height)
- the tyre hitting the body well before the UCA.
Here's a quick video demonstrating how the CV is fine even at extreme uptravel angles.
Here at VMN, we've sold all of the types of diff drops discussed in this article. We now only sell the Buds Customs 35mm low profile diff drop becasue nothing comes close to it.
You can get your diff drop from VMN here