Bulletproofing has long been a buzzword in the diesel industry, but is anything ever really bulletproof? The answer is no. Even balanced and blueprinted engines—pieced together with the strongest internals on the market—can pop if neglected or pushed too far. Sure, built engines, performance transmissions, and competition caliber injection systems are designed to withstand or facilitate huge horsepower, but you can’t simply add these things and never think about them again. At some point, depending on your driving habits, power level, how you use your truck, or because of age, you’re going to have to break the seal on that indestructible engine or transmission, along with having your injectors overhauled from time to time.

If you think you can install a built transmission and simply walk away, forget about it. While a built automatic can last up to a decade, at some point it’ll be due for more than just a simple service—especially if you’re using it to compete at the drag strip or hooking your truck to the sled.
Any time you’re going to be performing boosted four-wheel drive launches at higher power levels, do yourself a favor and opt for a converter with a billet stator. Here, you’re looking at the only billet stator on the market for Ford E4OD/4R100 torque converters. It resides in a triple-disc unit from John Wood Automotive that was CNC-machined by Sun Coast Performance.
An aftermarket converter designed to handle big torque should have a forged- or billet-steel front cover and furnace-brazed internals for optimum strength, a true triple-disc clutch with a quality friction material properly bonded to each disc, and a billet clutch piston. As mentioned, a billet stator is a wise decision for competition use, but it should also be considered in high-horsepower trucks that tow.
After more than eight years of harnessing 150 hp more than what it was originally built to hold, this E4OD, pieced together by John Wood Automotive, was due for a new converter and fresh overdrive clutches. Of course, in eight years’ time a lot of advancements had been made for the E4OD/4R100 platform, so many of those upgrades also made it into the build when it was pieced back together.
A billet-steel flex plate is a must-have item for any truck making 550 hp or more. Why? Because 550 hp likely means 1,000 to 1,200 lb-ft of torque—and immense low-rpm torque is known to tear the center sections out of factory flex plates
Aftermarket injectors and high-pressure fuel pumps are sizable investments, especially on common-rail engines, so take care that yours only see the cleanest fuel possible. Change fuel filters and drain your water separator (if applicable) every other oil change, or at least once a year.
After six years of loyal service, these Stage 4 hybrid 7.3L injectors were sent in to Unlimited Diesel Performance for inspection and a refresh—and we’re glad we did it when we did. Not that they were getting ready to fail, but some wear and tear was discovered on the plungers during teardown, along with a few solenoids not passing spec and requiring replacement. There is no way to diagnose this other than pulling them and sending the injectors in, as there were no warning signs that they were in need of some TLC.
As you can imagine, performance applications are harder on valve train components. With added rpm, boost, and drive pressure in the mix, valve adjustment becomes even more important. This is especially true for 24-valve Cummins applications. Many Duramax-centric shops believe that valve adjustments should be carried out any time the heads are removed or the valve covers pulled.
The aforementioned Stage 4 hybrids were also fitted with brand-new 200-percent nozzles and flow-tested (350ccs) while in Unlimited Diesel Performance’s care. There is no set timeline on when to replace injector nozzles, but it’s important to know they too don’t last forever—or even as long as a factory nozzle. This is because a larger hole size means more meat has been removed from the nozzle itself. When you get into competition-size nozzles (400-percent and larger), it’s not uncommon for a nozzle to crack at some point.
Pulling the injectors on many engines allows you to take a look at the rocker arms, inspect the injector wiring, test glow plugs (where applicable), and even access your head stud nuts for a re-torque or torque check. Again, just because you’ve added stiffer valve springs, stronger pushrods, or even built the engine, it’s still wise to take a peak inside the engine whenever (and wherever) possible, even if it’s part of a separate repair or upgrade.
Though it’s a bit extreme for street-driven trucks, at the high-end of diesel drag racing and truck pulling, it’s normal for engine builders to take a peak inside of these monsters at least every other year, if not every off-season. Thanks to stronger, deck-plated and billet-aluminum blocks, these 3,000 hp behemoths have proven highly durable, with many appearing brand-new inside after an entire summer of abuse. However, new pistons or rings, a quick cylinder hone, or fresh bearings provide good peace of mind for keeping these engines healthy. For an engine that cost well north of six figures, the added insurance is welcomed.
While you shouldn’t need to peer inside of the built engine under the hood of your daily driver every winter, after a handful of years it’s wise to semi-disassemble and take stock. Sure you can wait until a compression test is required or blow-by gets excessive, but then you’re already past the point of no return. Trust us, with engine turnaround time not exactly being quick in the diesel industry, setting aside some time to do a once-over every few years is much better than windowing a block and being without your truck for several months.
Not that it’s ever a bad idea with higher miles, but if you’re launching in four-wheel drive and under boost at the drag strip it pays to keep an eye on your U-joints, yokes, carrier bearing, and driveshafts. As soon as they’re visibly questionable or causing a vibration or noise, replace them. For the most part, the stock hardware (such as this recently replaced Spicer transmission slip yoke and corresponding 1330 series U-joint on an F-350’s front drive shaft) will suffice at the power levels most hot street trucks see.
Any time you’re building an engine that’s had a few miles put on it it’s wise to install new front accessory items. Things like water pumps, belt tensioners, idlers, serpentine belts, and even radiator hoses all have life expectancies that rarely exceed eight to 10 years. It’s best to start fresh not only internally during an engine build, but externally, to keep your truck on the road.
There’s no denying that traction bars absorb the brunt of abuse present in your driveline, so invest wisely here. If you’re running the type of traction bars that employ budget-friendly, off-the-shelf heim joints on your street-driven truck, they’re virtually guaranteed to make noise at some point, with many even needing replacing every year or two. DIY’ers have had great success using the greasable Johnny joints from Currie Enterprises over the years. Though they cost more money, the traction bars offered from One Up Offroad are designed to both perform and last indefinitely, thanks to their use of proprietary bushing joints (shown).
Of course, there are freak failures that can occur on any engine, built or not. Take this 6.7L Power Stroke for example. After its aftermarket oil pressure regulator failed, the lack of oil pressure led to several spun rod bearings. While this isn’t meant to scare you, it is the proof that anything can happen even if an engine has been balanced, blueprinted, and assembled with the best parts available.
If you’re running a built engine, chances are pretty good that you perform regular maintenance on your truck and use a quality engine oil. However, there are always truck owners that neglect to carry out proper maintenance intervals or forgo them altogether for excessive periods of time. Trust us, no engine (built or not) will last if it’s neglected. This means regular fluid and filter changes aren’t a recommendation but a necessity—especially on today’s common-rail engines

The simple truth is that there’s parts you’re going to have to replace eventually, whether you’re at 600 hp or 1,200 hp—even aftermarket components. Are those traction bars you bought years ago banging and clanging? Time for new heim joints. Has your brake wear increased since the addition of all that extra horsepower? Time to consider an upgrade in stopping power. How many years has your once-overbuilt transmission been dealing with ever-increasing horsepower? Better get it checked out before it fails and you’re out some serious money. The list goes on. For a behind-the-scenes glimpse at the repairs that are both expected and overlooked on built trucks, keep reading. It could mean the difference between your fun coming to an abrupt halt or continuing for years to come.

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