Upgrading the leaf springs on my 1987 Jeep Grand Wagoneer

Ever since I bought my 1987 Jeep Grand Wagoneer and began to modernize it, I’ve wanted to use the vintage Jeep as a tow rig for my 1978 Datsun 280Z on track days. While it certainly would have been simpler—and a whole lot cheaper—to purchase a 10-year-old SUV and slap on a hitch, there’s no rule that says tow vehicles have to be boring.

I made sure to bake in certain details to my project Jeep: Hydroboost brakes, a 3.73:1 rear gear ratio, and enough cooling for both the engine and the transmission to handle the relatively modest weight of my vintage Datsun. I also made sure that the truck’s AC blew cold. On a hot summer night, after a day spent baking inside the tin oven that is my Z, I want to haul home in some comfort.

Unfortunately, I overlooked a crucial area of my project—suspension—which put a serious damper on my towing plans. More accurately, I tried to save some cash with a workaround instead of doing things the right way from the start. The end result forced me to find an alternative tow machine at the last minute to save my final track date of 2022, teaching me an important lesson about not cutting corners.

Wag-sag blues

Anyone who has spent time around full-size Jeeps is familiar with the term Wag-sag, a gently sloping stance produced by rear springs suffering from three decades of gravity’s pull. Typically, Wag-sag manifests whenever there’s a bit of extra weight in the cargo area; sometimes, it’s visible even with passengers riding in the second row.

I was fairly certain that my own Jeep was riding on its original set of leafs, but, even when I packed the back to the brim with gear, my case of sag hadn’t seemed all that bad. This helped me justify the decision to replace only the rear suspension’s worn-out bushings and shocks (the latter with a new set of Bilsteins). Cost was also a motivating factor: if I replaced rear springs, I’d also have to do the fronts to avoid giving the truck a janky ride and a weird look. You have to pay for a lot of steel in a set of four new leaf springs, especially compared to what you’d pay for more modern, modestly-sized coils.

At the beginning of last summer, with towing finally on the horizon, I did make a pair of concessions. I ordered a Jeep-specific air lift kit that would fit between the top of the leafs and the frame, inflating to make up for any flaccid performance from the springs themselves. Next, I purchased a load-distributing hitch, something I had planned on buying anyway to help improve trailer stability, given the Jeep’s relatively short wheelbase. This system relies on a set of spring bars to reduce tongue load and control sway by moving some of the load forward to the tow vehicle’s front axle.

Dip, dip, dip

Each of these strategies had come to naught by the time I was ready to hitch up. My air spring kit was sold out nationwide, and even though a cracked cylinder head had sidelined my Z until the month of August, the extra months weren’t enough to account for the slack in the global supply chain. Undaunted, I scheduled a U-Haul rental so I could test the weight-distributing hitch before I headed down I-81 on my way to a date at Watkins Glen International.

The bumper dip after hooking up the 2200 pounds of U-Haul trailer to my Class IV hitch should have been my first clue. As you can imagine, doubling the weight by adding 2500 pounds of Datsun to the trailer sent the back end of my Jeep into the kind of squat seldom seen outside a dead-lift competition.

I went ahead with the test drive. The trip was short—a local jaunt to AGM Performance, where we planned to use a set of scales to install and adjust the spring arms for more effective tongue weight distribution—and eye-opening. Even at low speeds on city streets the Jeep’s steering felt like the front tires had been filled with helium. Asking the setup to turn and brake simultaneously was an exercise in wishful thinking.

Even more fanciful? The idea that we’d be able to link up a weight-distribution system to U-Haul’s finest flatbed. The spring arms proved to be far too short to connect to the triangle neck on the trailer itself. Finally, I did the quick online research that I could have done at any point that summer and discovered that the surge brake system on a U-Haul unit requires that the long neck remain mobile while towing. Even if I found a load-distribution system that would fit, it would effectively defeat the trailer’s stoppers, thus introducing a new element of danger into a brew that was already fairly sketchy.

Do-over time

While I might be a bit of a masochist when it comes to automotive projects, I wasn’t about to put anyone’s life in danger by dragging tail down the highway. Having exhausted all workarounds, I admitted defeat. It was time to get a new set of springs installed.

Fortunately, I had options. Despite the supply-chain situation, I was able to source a set of springs from BJ’s Off-Road without any delay. The Jeep supplier provided a choice between imported and USA-made steel, and, after a bit of forum browsing, I learned that the most recent batch of built-elsewhere springs had a tendency to sag after only a couple of years. It was an easy decision to spend the extra bit of money.

I was also able to locate a universal Air Lift kit online that had good reviews from fellow Grand Wagoneer owners. I wasn’t sure if the replacement leafs would need the extra help, but at this point I was done with penny-wise, pound-foolish decision-making. I wanted a bulletproof towing solution.

Installation was simple, for the most part: Unshackle the old springs, bolt up the new units. The old leafs were clearly on borrowed time: Corrosion patterns on the rear set showed that they had flattened out and had been sitting on the helper spring for who knows how many years.

Putting in the air shock kit was a little more challenging. The Grand Wagoneer’s gas tank is mounted on the driver’s side, an arrangement which leaves only a little room for positioning brackets and tools, but AGM eventually got the kit to slide into place. I opted against an in-vehicle air compressor—I didn’t plan on airing up or down on a regular basis—and told the shop to rout the lines into a Y-fitting so that I could fill both sides evenly from a single valve.

Banish the suspension blind-spot

I should have slapped on a new set of springs as soon as I bought my Jeep. The difference between how the Grand Wagoneer handled before the fresh springs and after is astonishing. Although I was afraid that the SUV would feel too stiff or jumpy (especially with about 20 psi of air filling the helper springs at the back, as per the manufacturer’s recommendation), ride quality had improved across the board.

Gone was a substantial amount of the shudder and wallow that the Jeep had displayed on very rough pavement. Longer corners no longer required tacking out with my knee and shoulder to counter-balance body lean, a feature of the SUV since day one of my ownership. The improvement was most noticeable when driving around traffic circles; previously, these induced terrifying amounts of tilt, forcing me to dramatically reduce speed on entry or risk an embarrassing re-enactment of Motor Week’s cringe-worthy slalom test.

Though Wag-sag is now banished, I still haven’t had a chance to tow with the new suspension yet, as the autumn track season came to a close before I could finish installing the springs. I’m looking forward to sampling the difference at my first time-trial date this spring. I’m also getting used to the extra two inches of ride height I’ve gained by returning to stock spec; the relative lift has changed not just how the vehicle looks, but also how it feels from the driver’s seat.

If all of the above seems incredibly obvious—fresh springs make an old suspension feel like new again—you’re right. That’s the reason I’m highlighting this particular oversight: If someone like me, who’s spent thousands of dollars modernizing my Grand Wagoneer’s drivetrain, brakes, and suspension, can skip out on something as self-evident as installing new springs, then I’m willing to bet there are other classic vehicle owners in a similar position.

There’s a compelling reason to whiff on this aspect of the build. It’s possible, as a driver, to get used to almost any aspect of how a vehicle performs, given enough time and mileage behind the wheel, and this is particularly true with suspensions. We’ve been conditioned to expect an older car or truck to feature a softer, more disconnected character out on the road, and tired springs fit perfectly into this preconception. Combined with the fact that, unlike a busted shock, there’s rarely any catastrophic clunk-and-shudder associated with a spring that’s past its prime, and it becomes extremely easy to just accept that your old rig’s worn-out chassis is merely a feature of its throwback appeal.

If your classic is currently riding on springs of unknown vintage, find out what an upgrade will run you. Chances are it’s a lot more affordable than you assumed. New springs will pay serious dividends not just in terms of comfort, but also in handling, braking, and safety. On today’s roads, old cars need every advantage they can get when dealing with modern traffic, and new springs are low-hanging fruit that’s well worth the pluck.

Check out the Hagerty Media homepage so you don’t miss a single story, or better yet, bookmark it.