-ADVERTISEMENT-

How to Bulletproof Your GM’s IFS

After a decade of proving itself in the truck-pulling game, it’s safe to say the independent front suspension found under ’01-present GM HD trucks is a viable system to campaign with in the dirt.

-Advertisement-
-Advertisement-

Although it gets a bad rap from straight-axle fans, the AAM 9.25-inch IFS axle is actually a fairly stout unit in stock form. It incorporates an aluminum (“clam-shell-” style) carrier that houses a 9.25-inch diameter ring gear, and accepts 33-spline CV-style axle shafts. However, when it comes to upping horsepower and torque levels for competition purposes, GM’s IFS can (and should) always be improved upon.

With there being no shortage of Duramax mills cranking out four-digit horsepower these days, it’s no wonder so many aftermarket IFS parts exist for late-model Chevy and GMCs. Whether it’s suspension, axle or steering related—or a combination of all three—if your IFS has a problem, you can rest assured that there’s a fix for it.

The following pages showcase the parts that allow the factory-based AAM 9.25 IFS system to survive the extreme abuses of sled pulling. From tie-rod sleeves to front lockers and high-strength, alloy-steel axle shafts, there’s something here for every power level. DW

Aftermarket tie-rod sleeves vastly improve the overall strength of the factory tie rods on ’01-present GM trucks, keeping them from bending or even breaking, and stop those hard-to-watch toe-in scenarios from occurring. Most sleeves thread onto the factory inner tie rod, adding considerable strength in its weakest section (the area between the steering rack and the outer tie rod). Our advice is to stick with stainless-steel sleeves, because they won’t rust (i.e. easing future front-end alignments).

Check out the size difference between the stock tie-rod and a stainless-steel tie-rod sleeve from Merchant Automotive. The outer diameter of a factory tie rod on an ’01-’10 GM three-quarter-ton or one-ton truck measures 14.2mm, while the Merchant units increase their girth to 25.5mm. Running just $79.95, these tie-rod sleeves are just about the cheapest insurance your GM’s steering system could ask for.

The installation process for tie-rod sleeves is a piece of cake. Even for a first-timer, sleeves can be added in a matter of minutes. You simply discard the factory jam nut, remove the outer tie rods (counting the number of revolutions it takes to detach them), thread the tie-rod sleeve on, and reinstall the outer tie rod.

Going beyond tie-rod sleeves, several companies offer complete tie-rod assemblies. These Stage 1 tie-rod assemblies from PPE feature brand-new OEM inner and outer tie rods, and will come fitted with 304 stainless-steel tie rod sleeves. At $479.99, the Stage 1 kit is a budget-minded option for truck owners with ball joints that are already worn out.

Building on its Stage 1 tie-rod assemblies, PPE’s Stage 2 package for ’01-’10 trucks incorporates burlier components. For instance, the toe-adjusting shaft is 48-percent bigger than the factory one, while the tie-rod body itself is 40-percent bigger. In addition, the outer ball joint is 14-percent bigger and the inner ball joint is 28-percent larger than stock.

The Key to Maximizing IFS Performance and Durability:

The AAM 9.25 IFS system under ’01-present GM trucks utilizes CV shafts (also known as half shafts) to transmit horsepower and torque from the differential to the front wheels. Constant-velocity (CV) joints are used to handle torque transfer while still allowing steering and suspension inputs from the driver.

The front end of this ’01-’10 includes four key joints. The two innermost joints (“A”—located on each side of the differential side of the half shafts) are tripod joints, which cope with axle plunge and angle changes in order to atone for the suspension travel. The outer CV shafts (“B” —one on each side) incorporate six-ball Rzeppa joints, which don’t plunge at all, but are capable of handling more angle (for the steering).

-ADVERTISEMENT-

The key to optimizing this system’s durability and performance potential is to keep everything that is suspension-, steering-, and axle-related from experiencing odd angles. The more angles seen by the CV-shafts, ball joints and steering components, the weaker the front end becomes. As a general rule of thumb, it’s best to have the CV shafts parallel to the tie rods when the truck is making its peak power (just like what’s pictured).

PPE’s Stage 3 tie-rod assemblies (available for both ’01-’10 and ’11-newer trucks; the ’11-plus units being shown here) represent some of the toughest units you’ll find in the aftermarket. The forged tie rods measure 1.50-inches wide and feature massive 2-1/3-inch ball joints (including a 30-percent larger inner ball joint).

While tie-rod sleeves are usually the first modification made to the AAM 9.25 IFS system, most truck owners who plan to sled pull (or drag race) typically add pitman- and idler-arm braces at the same time. The purpose of a pitman- and idler-arm support kit is to stop the steering center link from twisting under load and causing a toe-in situation. PPE and Cognito Motorsports offer quality (and highly popular) pitman and idler arm support kits.

Here you can see how the pitman- and idler-arm support kit installs. The braces keep the factory center link from rocking forward and backward, yet still allow the side-to-side movement required to steer the truck. For hot street trucks that make roughly 500 to 750hp and that hook to the sled occasionally, tie-rod sleeves and a pitman- and idler-arm support kit is usually sufficient in standing up to the abuse.

Taking things a step beyond simply reinforcing the factory pitman and idler arms, PPE offers what it calls its “Race” pitman and “Race” idler arms. Designed to work with PPE’s Race-series center link, they both accept a larger 7/8-inch bolt assembly (via a pressed-in sleeve), with the Race pitman arm being fitted with chromoly joints held in place with a snap ring.

With a lot of trucks being lifted, it’s important to select the right torsion-bar key for your application. Again, if you plan to sled pull, drag race or even venture off-road, it behooves you to keep the CV shafts at the optimum angle (parallel with the tie rods). The most versatile keys we’ve come across are the MaxxCam 2 units from Suspension Maxx. They offer seven incremental adjustments, so you can obtain the exact height, stance and CV angle you’re after.

Once enthusiasts have upgraded the tie rods, or installed sleeves and pitman- and idler-arm braces, the next step usually entails a locker. For off-roaders, sled pullers, and drag racers alike, the ARB Air Locker (RD197) remains popular. Its big claim to fame is that it doesn’t sacrifice your truck’s highway driving manners, yet with the flick of a switch, it can be locked in with 100-percent traction on demand.

Is IFS the key to the Duramax’s Success in the Dirt?

Since the nature of an IFS system is to provide maximum traction at all times (no matter the terrain), this might be the key to so many GMs ending up out front at a lot of truck pulls. Let’s face it: if anything, it’s the Duramax-powered trucks that are down on horsepower, compared to the Cummins-powered rigs. But, we’ve seen GMs take home the win at all kinds of local and national events.

Of a two-piece design with forged gears and a solid internal locking mechanism, the ARB Air Locker is simple yet rugged. The Air Locker RD197 comes with an air line, a solenoid valve, an activation switch and bulkhead fittings; however, it requires a 12-volt air compressor that must be purchased separately.

Although no longer in production, the Eaton ELocker was once the go-to unit for hot street trucks that spent a lot of time hooked to the sled. While many serious sled pullers use an ELocker to lock both the driver and passenger axleshafts together, you’ll find a low-budget, welded differential on a lot of purpose-built pulling rigs.

While the verdict is still out as to whether or not a straight center link is warranted for high-horsepower GMs, everyone agrees that—at the very least—a stabilizer should be used on trucks that intend to sled pull competitively. Once the center link rotates (an OEM ’01-’10 unit is shown), the front tires toe-in, traction is lost, and permanent damage to the steering system can occur.

For ultimate rigidity and control between the steering wheel and tires, PPE’s 304 stainless-steel center link might be it. Its straight design (i.e. “straight center link”) eliminates the toe-in and toe-out instances the factory unit is known to allow while sled pulling or drag racing.

Dirty Hooker Diesel’s center-link steering stabilizer bracket is a more budget-friendly way to address the stock center link’s tendency to flex under load. Designed for factory-ride-height trucks only, the direct bolt-on unit incorporates a three-sided mount bracket that utilizes the front differential as its triangulated support, which keeps the steering system straight and true. It can be installed in 15 minutes, it doesn’t alter your front-end alignment, and it runs for just $160. Two versions are offered: one for ’01-’10 trucks, and one for ’11-present.

This is what a typical center-axle disconnect (CAD) failure looks like in the factory front differential. At the mercy of extreme stress and torque, the sliding collar is exposed to constant twisting and binding; when it finally goes, it basically explodes. Due to the amount of labor required to fix it—running up the cost of the repair considerably—many serious sled pullers (and a lot of novice enthusiasts) upgrade to stronger axle shafts and do away with the center-axle disconnect altogether.

Here’s a permanent fix for a failed center-axle disconnect: Fleece Performance Engineering’s TufShafts. They eliminate the split passenger-side axle shaft (the side that breaks), and are made from high-strength, HyTuf material (a low alloy steel used regularly in the aviation industry).

Because Fleece Performance Engineering’s TufShafts do away with the center-axle disconnect mechanism, it means the front driveshaft will spin permanently, which can lead to some vibration on lifted trucks driven on the street or at highway speeds. However, with the differential unlocked, no turning radius will be sacrificed.

For truck owners that want to retain the factory-axle disconnect (say, on street-driven trucks), Dirty Hooker Diesel offers this custom sliding collar. The billet unit is a direct replacement for the powdered metal, factory sliding collar and is capable of handling much more shock load.

Another option for eliminating a failed center-axle-disconnect scenario comes from RCV Performance Products. Fittingly named the Ultimate IFS CV Axle, this is the cat’s meow in the sled-pulling segment. Using a six-bearing inner CV joint to distribute torque (versus the weak OE tripod design); a housing, bearing cage, inner race and axle shaft made from aircraft-quality, high-alloy steel; and vastly improved articulation, RCV’s product is as indestructible and versatile as they come.

SOURCES
ARB

866.293.9078
ARBUSA.com

Cognito Motorsports
866.426.4648
CognitoMotorsports.com

Dirty Hooker Diesel
989.479.0444
DirtyHookerDiesel.com

Fleece Performance Engineering
855.839.5040
FleecePerformance.com

Merchant Automotive
866.399.7169
Merchant-Automotive.com

PPE
714.985.4825
PPEDiesel.com

RCV Performance Products
815.877.7473
RCVPerformance.com

Suspension Maxx
888.629.9226
SuspensionMaxx.com