If you've been feeling a bit too much "slap" or chucking while you're cruising down the highway, it's probably time to look at your fontaine fifth wheel adjustment. There is nothing quite as annoying—or potentially sketchy—as a connection that feels loose every time you hit the brakes or step on the gas. Most drivers know that Fontaine makes some of the sturdiest gear on the road, especially with their "No-Slack" technology, but even the best tech needs a little fine-tuning every now and then.
The whole point of the Fontaine design is to keep things tight automatically, but reality on the road is a bit different. Parts wear down, grease gets old, and eventually, you're going to need to get in there and make a manual tweak. It isn't rocket science, but if you do it wrong, you're either going to have a fifth wheel that's impossible to uncouple or one that rattles your teeth out.
Why the No-Slack System is a Bit Different
Most people love Fontaine because of that No-Slack branding. The way it's supposed to work is that a spring-loaded wedge self-adjusts to take up the gap between the kingpin and the lock jaw. In a perfect world, you'd never have to touch it. But we don't live in a perfect world; we live in one with road salt, grime, and thousands of miles of vibration.
When that wedge stops moving freely, or if the jaw itself starts to show its age, the "automatic" part of the system might need a helping hand. Doing a fontaine fifth wheel adjustment is really just about making sure that wedge can do its job properly. You're essentially resetting the baseline so the spring can keep the pressure where it belongs.
Signs You Need to Tweak the Adjustment
You'll usually know something is off by the "feel" of the truck. If you're getting a hard "thump" when you take off from a stoplight, that's the kingpin sliding inside the lock. It might only be a fraction of an inch, but when you're pulling 80,000 pounds, you're going to feel every bit of it.
Another sign is difficulty uncoupling. If you find yourself having to back into the trailer with a massive amount of force just to get the pull handle to release, your adjustment might actually be too tight. It's a bit of a Goldilocks situation—you want it just right. Not so loose that it rattles, but not so tight that the locking mechanism is under constant, extreme tension when you're trying to park.
Getting Prepared for the Job
Before you go grabbing wrenches, you've got to make sure the fifth wheel is clean. I know, nobody likes scraping old, crusty grease, but you can't see what you're doing if the whole mechanism is buried in three inches of black gunk. Give it a good degreasing if it's looking rough.
You'll also need a couple of basic tools. Usually, a large flat-head screwdriver and a couple of wrenches (often 15/16" or similar, depending on your specific model) will do the trick. You also want to make sure you're parked on flat ground with the trailer dropped or, better yet, use a kingpin tool if you have one. Using an actual trailer for the adjustment is fine, but a dedicated kingpin gauge makes it a lot more precise because you aren't fighting the weight of the trailer.
The Actual Adjustment Process
Once you're ready to roll, the first thing you're looking for is the adjustment bolt on the side of the fifth wheel. On most Fontaine models, like the 6000 or 7000 series, this bolt controls how far that wedge can travel.
Setting the Wedge Gap
The goal here is to make sure the wedge isn't bottoming out. If you look at the mechanism while it's locked onto a kingpin, you'll see a wedge that slides behind the jaw. If that wedge is shoved all the way in and touching the stop, it can't take up any more slack. That's usually when the rattling starts.
To fix this, you'll want to loosen the jam nut on the adjustment bolt. Then, you turn the adjustment bolt itself. Usually, turning it clockwise will pull the wedge back, and counter-clockwise lets it go deeper. You're looking for a specific gap—often around 1/4 inch to 1/2 inch between the wedge and the stop—but always check your specific model's plate because they vary a bit.
Testing the Snap
After you make a change, you've got to cycle the lock. Open the fifth wheel using the pull handle, then lock it back down onto your kingpin tool or trailer. Listen to the sound it makes. It should be a crisp, metallic "clack." If it sounds sluggish or muffled, something is binding.
Do this a few times. Don't just adjust it once and call it a day. The parts need to settle. Sometimes the wedge won't seat all the way on the first try, so give it a few cycles to make sure the fontaine fifth wheel adjustment is actually holding where you want it to.
Don't Forget the Grease
You can spend all day turning bolts, but if the pivot points are dry, the system is going to fail anyway. The No-Slack system relies on that wedge being able to slide smoothly. If it's bone-dry, the spring won't have enough "oomph" to push the wedge into place, leaving you with a loose connection even if the bolt is perfectly adjusted.
While you're under there, hit all the grease zerks. Use a good quality extreme-pressure grease. It handles the constant pounding of the kingpin much better than the cheap stuff. Also, make sure the top plate is lubricated. A dry top plate can cause steering issues and put weird lateral stresses on the locking mechanism, which can throw off your adjustment over time.
Common Mistakes to Avoid
One of the biggest blunders is over-adjusting to compensate for a worn-out kingpin. If your trailer's kingpin is hooked or worn down past its service limit, no amount of fontaine fifth wheel adjustment is going to make it safe. You'll just end up damaging the fifth wheel jaws. Always take a quick look at the kingpin itself; if it looks like an hourglass, the trailer is the problem, not your truck.
Another mistake is forgetting to tighten the jam nut. It seems like a small thing, but those bolts see a ton of vibration. If you don't lock that jam nut down tight, your adjustment will vibrate loose within a few hundred miles, and you'll be right back where you started, wondering why the truck is thumping again.
Final Safety Check
Once you've got everything dialed in, do a proper tug test. It sounds basic, but it's the most important step. Hook up, raise the landing gear just an inch or two off the ground, and give it a good pull. Then, get out and visually inspect the lock. You want to see that the jaw is fully wrapped around the kingpin and that the handle is all the way in.
If everything looks solid and the "slap" is gone when you're driving, you've nailed it. Regular maintenance on your fontaine fifth wheel adjustment doesn't just make the ride more comfortable; it saves wear and tear on your drivetrain and keeps things safe for everyone on the road. It's one of those quick jobs that pays off every single time you shift into gear.