How to Install Air Bags on a 2017–2019 Ford F-250 or F-350

This guide walks through fitting the BOSS rear air bag kit for the 2017–2019 F-250 and F-350 Super Duty (BOSS LA-120, for trucks with a 4″ rear axle). It follows BOSS's own fitting instructions, which are also on the product page as a PDF. The triple bellow version uses the same instructions.

Always follow the instructions that come with your kit. This article is an overview to help you plan the job.

Before you start

• Check you have the right kit: the vehicle is printed on the instruction sheet.
• Work on one side of the truck at a time. Jack up one side and put a jack stand under the axle. Never work under a truck held up only by a jack.
• You'll need a socket set, cable ties, a sharp knife for the air line and soapy water for leak checks.

1. Assemble the air bags

Bolt the top and bottom end plates (the brackets) to the alloy rings on each bag, using the 6 bolts and spring washers at each end. Leave the bolts loose enough to rotate the plates, so you can line them up with the U-bolts and bump stop holes.

2. Fit each bag

1. Remove the upper rubber bump stop from the chassis.
2. Sit the bag assembly on the axle and line up the top and bottom brackets.
3. Fix the bottom bracket to the axle with the U-bolt clamps supplied.
4. Tighten the top bracket to the chassis using the large washer plates supplied and the original bump stop nuts.

Two details from BOSS's diagram:

• The top bracket mounts facing the inside of the chassis rail. The rail has a bulge where the bracket rests: position the bracket against the bulge and tighten it there.
• The bag plates are offset. On both sides, the offset faces the differential.

3. Tighten the bag bolts

With everything aligned, tighten the 6 bag bolts at each end, leaving a gap of about 1–2 mm between the two plates. Work evenly from one side of the plate to the other, the way you tighten wheel nuts, so the gap is even all the way around. Don't over-tighten: that can cause leaks.

4. Air line and valves

• Mount the Schrader valve panel somewhere easy to reach.
• Keep the air line at least 100 mm (4 in) from the exhaust.
• Cut the line clean and square with a sharp knife, with no burrs, and don't squash it.
• Push the line firmly into each fitting, then give it a short, sharp tug to make sure it's seated.
• Don't use thread tape, sealant, oil or grease on the line. It will cause a leak.
• Zip-tie the line to the chassis.

5. First fill and leak check

After fitting, inflate the bags to 80–100 psi once, then let them down to your normal pressure. This lets the alloy rings bite into the rubber and seal. Spray soapy water on every fitting: bubbles mean a leak. If a fitting leaks, pull the line out, rotate it and refit it, or re-cut it. If air leaks around the alloy ring, remove the 6 bag bolts and rotate the ring 90 degrees.

Finish by fitting the door decal in the door jamb.

Safety

• The bags help the truck sit level when it's legally loaded. Don't exceed the truck's GVWR.
• Never inflate the bags above 200 psi, and don't drive with them bottomed out.
• Retighten any factory bolts you loosen, such as U-bolts, to Ford's torque specification, and replace U-bolts that look damaged.

Need the kit? BOSS rear air bag kit for the 2017–2019 F-250 and F-350. Other years: Ford kits. BOSS also posts installation videos on youtube.com/bossairbagsuspension.