Toyota 4Runner, Third Generation: Trail Suspension, Part 4

All-Pro one-inch diff & top-hat spacers we call it the lift-drop.

Mar. 08, 2010 By Justin Fort

All-Pro Off-Road's 1-inch spacer.

As simple lift combinations go, a set of one-inch spacers provides most coil-sprung trucks an effective increase in ride height. Some kits are not so ideal, and some spacers are best used as street-only or light-duty improvements in altitude, but for the Toyota crowd, the “top-out” spacer is a sensible and effective lift for 4Runner, Tacoma and FJ owners.

Call them what you like, but the top-hat/top-out/spacer provides an inexpensive and ready lift – All-Pro Off Road (, 951.658.7077) builds its kit with a poly-based puck. The poly spacer should be used in tandem with the matching one-inch diff-drop, a correction for the increased constant-velocity angles created when lifting an independently suspended vehicle. 

Simple as it seems is a crock. In the case of our oft-flogged and eternally adulterated gen-three 4Runner, the diff-drop worked fine, but the All-Pro one-inch poly spacer was compromised by our previous parts selections. We intended to use the spacer to plus the front end to an honest three inches, pushing the limits of happy half-shafts to experiment with workable droop within the OEM geometry. Unfortunately, with approximately 1.75- to 2-inch lift already achieved with a set of TRD Tundra coils on adjustable Bilsteins 5100s (at their lowest setting to allow as much flex as possible), the one-inch All-Pro top-out created too much lift, and we couldn’t put the front back together without serious gymnastics or damaging something.

New diff-drop hardware with original formed OEM washer.

All-Pro Diff-Drop for Happy CVs
Starting with the easiest part of the lift-drop, we slid beneath the 4Runner to decipher what went where. The diff-drop is a good idea for a 4Runner with a 1- to 3-inch lift. It mitigates some of the increased half-shaft angle and reduces wear accordingly (not a big deal at road height – it’s the high-articulation moments that cause damage). The diff pivots front-to-rear, so you’ll be lowering the forward mounts a tad. It takes a small bite out of clearance, less than an inch with the skid-plate properly spaced (as we’ll describe later). Aftermarket skid-plates units usually get back the inch lost with the diff-drop. Seeing as we have to splat the IFS end of this 4Runner to contact anything remotely ground-like, it’s a marginal loss. Trust us, we’ve tried.

The only difficulty you’ll likely see, especially with a salted-up truck, is breaking the sticktion of the two Grade Massive through-bolts at the forward differential mounts. With a strategic daub of Liquid Wrench and some leverage, they came along (never forsake leverage: it’s better than popping a vein or having to admit rust is stronger than you). We loosened both and left one in a few threads to keep things in place while slipping in the new spacer and bolt (you’ll reuse the formed OEM fender washers). The spacer sits between the mounts and the sub-frame. We dressed the threads with a locking compound before sending them home. The All-Pro instructions didn’t suggest doing so, but this seemed like a time when thread-lock wasn’t a bad idea.

Not exactly one inch – the All-Pro diff-drop measures 3/4 inch pre-washer.


Support the diff with a jack if you please. Here, both spacers are fitted, bolts loosely threaded.

The only ingenuity required for the diff-drop was making the forward skid-plate fit properly. With the diff-drop installed, the backing mounts of the plate don’t reach the sub-frame. We keep a stock of “thick-ass” washers (a fender washer stamped from 1/4-inch mild steel that serves well for test fits and experimentation) and two of them tack-welded together formed an ideal kickout for the skid-plate to attach correctly. We needed longer bolts to get proper thread purchase, so a few leftover Grade Massive bolts off a bugeye WRX did the trick.

Diff-drop, firmly installed. Neat trick: that lower-arm adjuster cam is worth about 1/2-inch more footprint on each side (if we’d just bother to do so).

Top-Hat Complications: Good Spacers, Wrong Recipe
On to the top-out spacers … the key thing to consider is the magnifying effect of the pivoting A-arms – one-inch at the shock becomes two at the hub, the increase in overall shock body length approximately doubling effective lift. It’s different for a spacer inside of the shock (beneath the top-hat), because that spacer increases spring tension but is held to the same maximum length, lifting the vehicle because the spring is stiffer, not because of increased length of the coilover.
Longer Subaru-sourced bolt used for the skid-plate is on the left (as is another easy emergency spacer). Any high-grade metric bolt will do.

As you’ve read, we’ve used the pliable, rock-friendly and simplistic “Tundra lift” to raise the front end of our 4Runner, and the All-Pro one-inch top-out spacer was intended to bring the rig to its maximum IFS lift. The Tundra lift, using a new TRD spring, had some sag inevitable. We weren’t sure exactly how much, but a 1.5- to 1.75-inch final height was expected. With about two inches of lift added with the one-inch spacer, we’d push the mechanical limits of front travel with this 4Runner. Part of the experiment was to decipher what parts would make it work (things like droop-straps and bar discos), and then get an idea of what would break.

After a host of attempts to fit the one-inch spacer with the TRD Tundra/Bilstein 5100 combo, we concluded that without altering the upper A-arm, the one-inch spacer wasn’t going to work. We dropped the lower arm, disconnected everything but the kitchen sink, and the one-inch spacer created too much coilover length for our TRD/Bilstein combo. One of the few downsides of the Tundra coil swap is that the coils’ outer diameter is larger than the 4Runner spring (about two centimeters), so they take up more space in the working area around the shock itself, and the upper A-arm or OEM ball-joint contacts the coil at max-droop. A narrower spring, such as the OEM 4Runner unit, would have made assembly easier (the upper arm could have drooped further), and a uniball or high-travel ball-joint would enable more articulation at the upper arm’s limits. A modified factory A-arm (we’re going to try a set of these down the road, with a small-shop recipe on how to build them yourself) or tubular-uniball upper arm like that offered by All-Pro, would also increase the potential travel of the upper arm. We’ve yet to cross those bridges.

Note the skid-plate droop – minimal, even spaced out 1/2-inch.


All-Pro’s one-inch top-out spacer in place; extended press-in studs are included with locknuts and new top-hat isolator bushings.

IFS and Spacer Thoughts from a Pro
Not being able to make the All-Pro top-out poly spacer work with our combo left us with inquiring minds. A conversation with Jon Budrant of All-Pro filled in most of the blanks. He fleshed out the math of a one-inch spacer, a few reasons for a poly spacer (including vibration absorption), and the ins and outs of tubular A-arms (not necessary in this case, but useful in others). Most importantly, Budrant explained that in our case, considering the spacer can’t fit, kicking up the variable perch on the adjustable Bilstein 5100s (the BE5-6929-HO, to be exact) would make almost no difference in ride quality with the progressive TRD Tundra springs (48131-AF090 and 48131-AF100, left and right). We’d counted on the progressive rates to smooth the ride on-road, but there are five steps on the shock body and each lifts the perch about a centimeter. That’s our next step (no pun intended).

Despite taking the front suspension apart, the longer spacer and coilover combo wouldn’t fit without doing scary leverage things.

In reality, we’re making the most of the limits imposed by an independent front suspension. If you’re in the mood for more than three inches of overall lift for your 4Runner – more than IFS alone can provide – it’s time to consider a body lift, or using a solid axle up front. We want to keep this rig independent, though, so we’ll keep trying.

One of the pinch-points – upper ball-joint, meet Tundra coil, despite reducing the ball-joint perimeter as much as reasonable.

It’s important to avoid throwing out the baby with the bathwater here – the TRD Tundra/Bilstein coilover is wonderfully functional, and a great foundation for a trail-ready 4Runner. Forcing the spacer to work with extant parts could have rendered them less useful. These poly spacers are nice pieces, though, and the All-Pro kit is easy to complete; it’s just not ideal for the TRD Tundra/Bilstein 5100 combo. If you want a simple two-inch lift for a 4Runner on stock shocks and springs that would match a two-inch rear spring, the All-Pro spacer is perfect. It would probably work with several of the shorter Tundra combinations too, as with the two-wheel drive non-TRD set of coilovers we kept seeing at the junkyard. Can you say “bargain lift”? Stay tuned, and call All-Pro to learn more.

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