2021 RAM 3500 Reliability: Heater-Relay Repair History, Wheel Studs and Cummins Load Limits

The 2021 maximum is a particular high-output configuration

RAM's exact-year matrix, dated 28 October 2020, separates standard-output Cummins/68RFE and high-output Cummins/Aisin AS69RC six-speed diesel branches. It publishes 37,100 lb for the Regular Cab Tradesman 4x2, 8-ft-box, dual-rear-wheel high-output truck with a 4.10 axle, 14,000-lb GVWR and 45,000-lb GCWR.

That is a different exact-year row from the 35,100-lb 2020 maximum documented in the linked prior-year guide. It does not establish that a used 2021 truck is more durable, that every 4.10 dually has the same rating, or that an aftermarket modification creates the factory configuration.

Verify the engine/transmission branch, cab, box, drive, wheel count, axle and labels before using a seller's capacity claim. The standard-output diesel still uses the 68RFE, and a single-rear-wheel pickup can have the high-output/Aisin combination. A trim badge or 'Cummins automatic' description leaves essential selectors unresolved.

Follow Y08 to Y76 to 13A, rather than counting three independent defects

The 2021 model query returns 21V163000 / Y08, 21V798000 / Y76 and 23V060000 / 13A. The first record explicitly says it was superseded by 21V798; the second says it was superseded by 23V060. These are linked heater-grid-relay actions, not proof of three separate failures on each truck.

The earlier descriptions concern an electrical short in the intake-heater relay, with fire possible even when the ignition is off. Earlier operations included inspection, replacement if necessary and specified insulation work. The later 13A record states relay replacement and retains the instruction to park affected, unrepaired vehicles outside and away from structures until repair is complete.

Ask the manufacturer or dealer to reconcile the current VIN status and the actual final repair. Do not accept 'relay checked in 2021' as proof that the later action is closed. The historical query's 21V163 park-outside Boolean is false despite its remedy text containing a parking precaution; this guide relies on the explicit instructions and later superseding record rather than that flag.

This is evidence about an electrical relay. It does not measure grid-heater fastener ingestion, establish a general Cummins failure rate or endorse emissions-related deletion as a substitute for the manufacturer remedy.

Five other pickup-related entries require distinct records

The table separates curtain-airbag inflation, steering-column control and wheel hardware. A restraint-system repair invoice without a campaign identifier is not enough to establish which action was completed. Applicability and current completion must still be checked for the individual truck.

One model-query entry is explicitly not a blanket pickup campaign

Z20 / 22V140000 concerns an ABS software condition in which the ESC malfunction indicator may fail to illuminate. Its RAM 3500 population explicitly names cab chassis vehicles below 10,000-lb GVWR. Its appearance in the 2021 RAM 3500 results does not establish that a completed pickup belongs in that population.

Thus the nine retrieved entries comprise the three-record relay chain, five other entries discussed above and this application exclusion. They are not nine independently established pickup defects. Absence of a different campaign from this model query also does not certify a Canadian vehicle as clear.

Have current VIN evidence resolve eligibility, and investigate actual brake, stability-control or transmission warnings on their own merits. Excluding an inapplicable campaign is not permission to ignore a symptom. Similarly, ZA3's summary is not used to assign every Aisin-equipped truck to its population.

Water-in-fuel warnings are not all the same diagnostic event

The manufacturer-authored 2021 owner manual identifies two diesel fuel-filter assemblies. The pickup's second assembly is ahead of the rear axle above the driveshaft; the cab-chassis location is different. Service paperwork should identify both filters and the correct application rather than just 'diesel filter replaced.'

On the selected warning page, detected water is associated with the indicator and five chimes. The manual directs stopping the engine and draining water from both filters; if the indicator remains on, it says not to start before the water is drained to avoid engine damage. Fuel/water separators must not be drained with the engine running. Have a qualified technician follow the complete procedure rather than using this buying guide as a workshop shortcut.

The same page distinguishes a single chime with the warning: wiring or sensor trouble may be involved, requiring dealer service. That is not a reason to assume every warning is harmless. Record the actual warning behaviour, diagnostic findings and completed repair; do not infer pump replacement or fuel-system cleanliness from a cleared dashboard.

The reviewed 504-page manual is externally archived, second edition V1. Selected pages were checked, not the entire maintenance schedule. Historical wheel-torque information is deliberately not repeated because the later Y26/Y36 campaign corrects published instructions.

Selected 2021 rows retain the SO/HO and cab differences

These are factory completed-pickup examples, not ratings for an inspected VIN. All weight figures are pounds. RAM labels payload and maximum trailer values estimated, rounded to 10 lb and mutually exclusive. Actual equipment, occupants, cargo and tongue or pin load still consume capacity.

A defensible buying decision needs closed evidence gaps

The chart's notes require a fifth-wheel hitch above 23,000 lb and a gooseneck above 30,000 lb; they do not supply separate complete hitch-method matrices. A 37,100-lb trailer claim is not permission to ignore hitch ratings, axle limits, tire limits or actual loaded weights. The full exact-year towing guide remains the place for the wider 74-rating matrix.

Before purchase, obtain current Canadian VIN information, verify the relay's final repair history, separate curtain and steering-column invoices, resolve wheel-stud inspection and corrected instructions, and inspect fuel, transmission, brakes, tires, steering and suspension. Reject unsupported capacity claims and defer a decision while significant leaks, warnings or modifications remain unexplained.

No reviewed source establishes lifespan, comparative failure rates or a best-year ranking. Strong records and an independent inspection support judging a particular truck; a larger factory towing number or a tidy campaign list does not. Catalogue profiles are editorial references, not active offers, confirmed sellers or available inventory.

A replacement Aisin changes the K1 bulletin check

For this 2021 truck, Stellantis bulletin 21-002-23 Rev. B has a narrow replacement-history condition: the 2019–2021 model-year branch applies only when a complete NEW transmission was replaced between 1 February and 18 December 2022. It also specifies Aisin equipment and a vehicle build cutoff of 1 December 2022. Check AS69RC/DF2 identification and the replacement invoice; do not apply this K1 snap-ring bulletin to every original 2021 Aisin or a 68RFE. P0731-00 and loss of gears 1–4 warrant qualified diagnosis. This is not a failure-rate estimate, Canadian VIN clearance or a promise of current warranty coverage.