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ranch_owner_trucksOP
LeatherBillings, MT44 posts, joined Jul 2025
2021 Ram 2500 Limited6.7 Cummins, rear air
2021 Ram 2500 Limited, 6.7 Cummins, crew cab, 8 foot bed, factory auto-level rear air. 58k miles. pulls a 24 foot W-W stock trailer, gooseneck, about 13,000 loaded with pairs.
two things going on. first, three mornings this month the rear was sitting noticeably low when i came out, the compressor ran for a while on startup and then it leveled. second, last week i got "service air suspension" on the dash halfway to the sale barn in Billings. it cleared after a restart and has not come back.
i love the bed lower button for hitching. you drop the rear, back under, raise it, the ball lines up with the coupler and you don't touch the trailer jack. i'd hate to lose that. before i let the dealer start charging me, where do i look?
Ram's owner info pages at ramtrucks.com say almost nothing about troubleshooting it, just how the modes work.
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plano_platinum
Cloth SeatsPlano, TX14 posts, joined Jul 2025
2023 Ram 3500 Limited Longhorn6.7 HO Cummins
sag overnight that comes back up after the compressor runs is a leak almost every time. the system is not holding pressure when it's parked, it just refills it when you start it. the message on the road is usually the compressor running too long trying to keep up, it has a timer and gives up.
i had a 2019 2500 with the same setup before i went to Ford for a while. mine was a bag with a little rub spot on it.
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duramax_dealer_tech
VentilatedShreveport, LA61 posts, joined Jul 2025
GM dealer tech, 19 yrs2019 Sierra 2500HD SLT, L5P
GM guy, but air is air. spray soapy water on everything with the rear aired up and the engine off: both bags top and bottom, every push in fitting, the line where it runs along the frame, and the valve block. a small leak foams like a beer. do it in the shade or the water dries before you see anything.
if you find nothing, check the compressor intake filter and the relay before you buy a compressor. a tired relay makes it work long and look like a leak.
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diesel_tow_rating
LeatherGreeley, CO33 posts, joined Jul 2025
2021 F-350 Platinum SRW6.7, 16k lb fifth wheel
one thing worth saying for people who land on this thread later. the air keeps the truck level, it does not add capacity. a 2500 with rear air has the same rear axle rating and the same payload on the door sticker as one without, and with 13,000 on a gooseneck the pin weight is pushing 2,500 or so. you're probably fine on a 2500 Cummins but people do read "air suspension" and think it turned their truck into a 3500.
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ranch_owner_trucksOP
LeatherBillings, MT44 posts, joined Jul 2025
2021 Ram 2500 Limited6.7 Cummins, rear air
found it. left bag, the push in fitting on top had a crack you could only see with soap on it. probably from mud packing around it all spring and then freezing.
dealer in Billings wanted 380 to diagnose before they'd quote. parts store had a push to connect fitting in the right size for 14 dollars. cut the line back a quarter inch so it was a clean square end, pushed it in, soaped it again, no bubbles. truck sat level for four nights.
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mod_bryce_l
ModeratorBoise, ID112 posts, joined Jul 2025
2020 Silverado 3500HD High CountryL5P, dually
nice. one safety note for the next person who has to get under one of these. before you jack the rear or put it on stands, go into the suspension settings on the screen and put it in jack mode or alignment mode. if you don't, the system sees a corner drop and tries to level the truck while you're under it.
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ranch_owner_trucksOP
LeatherBillings, MT44 posts, joined Jul 2025
2021 Ram 2500 Limited6.7 Cummins, rear air
two weeks and two trips to the sale barn with a full trailer, it holds. compressor runs a few seconds on startup like it always did when new. the message has not come back.
i'll know for sure when the September nights get down in the 30s, that's when everything rubber on this truck shows its age.
