What we handle
GMC repair and diagnostics in Mays Landing, NJ
Eight bays, foreign and domestic, with the same GM MDI2 / GDS2 scan capability the Chevrolet dealer uses. We cover the routine work and most of the repair work the GMC dealer charges Denali-tier rates for, and refer the narrow set of items only the dealer can do.
Scheduled maintenance and fluids
Oil and filter on Dexos1 spec, transmission fluid exchange (Dexron VI), brake fluid flush, spark plug replacement, cabin and engine air filters, all called by the GM oil-life monitor and the factory mileage table.
Common examples: Oil: 7,500 to 10,000 mi (Dexos1), Transmission: 45,000 to 60,000 mi, Brake fluid: 3 years, 100,000 mi major service
AFM, DFM, and 8L90 shudder
The two failure modes that define modern GMC truck and SUV service: Active Fuel Management and Dynamic Fuel Management lifter collapse on the 5.3L L83 and 6.2L L86 V8 (2014 to 2019 Sierra, Yukon, Yukon XL), and the 8L90 8-speed torque-converter shudder (2015 to 2019 Sierra, Yukon, Canyon). Both are GM-shared platforms, so the repair is the same work the Chevrolet dealer does on a Silverado or Tahoe.
Common examples: AFM lifter replacement, DFM lifter replacement, 8L90 Dexron HP update, AFM-delete kit consultation
Duramax diesel: referred out
We do not service the Duramax diesel. The 6.6L LMM, LML, and L5P and the 3.0L LM2 light-duty diesel all go to a dedicated diesel specialist for engine, fuel-system, and emissions work, and we will point you to one. We can still handle the gasoline Sierra lineup.
Common examples: Diesel work referred out, Dedicated diesel specialist, We make the referral, Gasoline Sierra in-house
Referred to the GMC dealer
Active warranty service, GM and NHTSA recall service, factory software updates and module reflashes that require GM secure permissions, and high-voltage battery work on the Hummer EV (Ultium 200+ kWh, 800V) and Sierra EV go to the GMC dealer in Egg Harbor Township or Atlantic City. We help coordinate the handoff with documentation.
Common examples: Active warranty service, Recall service, Factory software flashes, Hummer EV / Sierra EV HV
If you have a Sierra 1500 with AFM lifter tick, a Yukon with 8L90 shudder, an Acadia with timing chain stretch, a Terrain with oil consumption, or a Canyon pushing 150,000 miles, we have done that work in this shop. Sierra HD Duramax diesel work goes to a dedicated diesel specialist, and we will point you to one.
Signs your GMC needs service
GMCs tend to telegraph trouble before it becomes a roadside event. The cold-start tick, the highway shudder, the regen cycle that will not finish, the timing chain rattle. Here are the symptoms we see most often, and what each one usually means before we put the truck or SUV on the lift.
AFM or DFM lifter tick on cold start
On the 5.3L L83 and 6.2L L86 V8 in 2014 to 2019 Sierra, Yukon, and Yukon XL, a ticking sound on cold start that does not quiet up usually means an Active Fuel Management or Dynamic Fuel Management lifter has collapsed. Same failure mode the Silverado and Tahoe community catalogued. Repair runs from lifter replacement to AFM-delete kit depending on engine condition.
8L90 torque-converter shudder at light throttle
A shudder felt through the seat at 35 to 50 mph under light throttle on a 2015 to 2019 Sierra, Yukon, Yukon XL, or Canyon is the 8L90 8-speed torque-converter shudder. GM issued a TSB calling for a flush to the Dexron HP fluid spec. The fix is well-documented and we do it routinely.
Check engine light, steady or flashing
Steady is an emissions or powertrain fault. Flashing means active misfire, do not drive far. On the L83 and L86 V8, a P0300 misfire often traces to AFM lifter collapse. On the Acadia and Canyon 3.6L, a VVT-system code often traces to timing chain stretch. The scan tool tells us which.
Duramax DEF or DPF warning
On the 6.6L Duramax LMM, LML, and L5P, a Diesel Exhaust Fluid warning or a Diesel Particulate Filter regen failure means the emissions system needs attention before the truck derates. We do not service the Duramax diesel; the DEF, EGR, and regen work goes to a dedicated diesel specialist, and we will point you to one.
Acadia or Canyon 3.6L V6 timing chain rattle
A cold-start rattle from the front of the 3.6L LFX or LFY V6 in the 2007 to 2016 Acadia or the 2015 to 2022 Canyon points to timing chain stretch. VVT system codes often follow. Catching it before the chain skips teeth is the difference between a chain job and an engine job.
Terrain 2.4L Ecotec oil consumption
On the 2010 to 2017 Terrain (and its Equinox twin) with the 2.4L Ecotec, excessive oil consumption from a piston ring design issue was the subject of a class action. We measure consumption, document it, and walk you through ring replacement versus short-block options based on engine condition.
Coolant or oil leak on the driveway
On the 5.3L and 6.2L V8, water pump and timing cover leaks are common with age. On the Acadia 3.6L, the water pump is driven internally by the timing chain, which changes the repair scope.
Hummer EV charging or HV warning
Early Hummer EV units have shown charging-system quirks tied to the Ultium 800V platform. High-voltage work goes to the GMC dealer; we handle tires, brakes, suspension, AC, and cabin systems on the Hummer EV and Sierra EV at standard independent rates.
Two or more at once, do not wait. GMC repairs are usually cheaper when caught earlier rather than later, and the AFM, DFM, and timing chain failure modes all get worse fast once they start.
GMC service for Mays Landing and Atlantic County owners
Same family, same eight bays, same corner of Mays Landing since 1981. We serve Hamilton Township, Egg Harbor Township, Northfield, Somers Point, Folsom, Buena Vista, and the rest of Atlantic County. Most GMC owners we see drive in from those towns plus Hammonton, Vineland, Millville, and the shore towns.
The nearest GMC dealer is in Egg Harbor Township or Atlantic City, fifteen to twenty-five minutes from our shop, so the dealer story for GMC owners is not about distance. It is about the Denali-tier labor rate the GMC dealer charges for the exact same Chevrolet-shared mechanical work. A Sierra Denali oil change at the GMC dealer often runs 30 to 50 percent above what the same service costs at an independent shop on the same engine. The dealer keeps the work that needs the dealer: active warranty, recall service, factory software flashes, and HV battery work on the Hummer EV and Sierra EV.
Helpful details to mention
- Vehicle year, model, and trim (Sierra 1500 SLT, Yukon Denali, Sierra HD Duramax, Canyon AT4, Acadia SLE, etc.)
- Mileage
- Which dash light is on, or what the driver information center is showing
- What changed and when (sound, feel, smell, performance, fuel economy)
- Most recent dealer or shop visit and what they did
- Whether the truck or SUV is still under GM factory or extended warranty
- Duramax diesel trucks: we refer those to a dedicated diesel specialist
The more we know up front, the more accurate the estimate and the timeline.
Customer proof
Service was performed quickly and the Kneble Team provided great communication throughout the visit.Robert Orzechowski, Google review
Questions before scheduling?
Talk with us about GMC Repair and Service in Mays Landing, NJ
Tell us the model, the year, the mileage, and what changed. If it is a routine item, we book the visit and quote it on arrival. If it is a dealer-only item, we save you the trip and tell you where to take it.
Service guide
GMC Repair and Service in Mays Landing, NJ Service Guide
Topic-based reference for the GMC and Chevrolet shared-platform reality, the AFM and DFM lifter failure mode that defines 2014 to 2019 Sierra and Yukon service, the 8L90 8-speed shudder fix, why Duramax diesel work is referred to a diesel specialist, and how the Magnuson-Moss Warranty Act protects GMC owners using independent shops.
In this guide
02 of 05, AFM and
AFM and DFM lifter failure on the 5.3L L83 and 6.2L L86 V8
The defining modern GMC truck and SUV failure mode. Active Fuel Management (AFM, 2014 to 2018) and Dynamic Fuel Management (DFM, 2019 and later) shut down cylinders to save fuel. The lifters that ride the cam lobes for those cylinders collapse with age, throwing a P0300 misfire, a check engine light, and the characteristic cold-start tick. The 5.3L L83 in the Sierra 1500 and Yukon, and the 6.2L L86 in the Sierra Denali and Yukon Denali, are both affected. Same failure mode the Silverado and Tahoe community has been documenting for years.
Read more about AFM and DFM lifter failure on the 5.3L L83 and 6.2L L86 V8
Symptom progression
Stage one: cold-start tick that quiets after a minute. Stage two: persistent tick with intermittent misfire codes. Stage three: P0300 misfire, dropped cylinder, possible camshaft damage from a flattened lifter lobe. Catching it at stage one or two is the difference between a lifter job and an engine job.
Repair scope
On a healthy engine, lifter replacement with updated GM lifters. On engines with damaged cam lobes, lifter plus camshaft. On engines that have run misfiring for thousands of miles, valve-train and head work. We also consult on AFM-delete kits for owners who want the failure mode designed out for good (the kit blocks the AFM oil-control circuit and locks the lifters in their non-collapsing position).
Tell us what changed, when it started, and what you drive. We can help decide whether to start with an inspection, alignment check, or related repair.
03 of 05, The 8L90
The 8L90 8-speed torque-converter shudder fix
On 2015 to 2019 Sierra 1500, Yukon, Yukon XL, and Canyon equipped with the GM 8L90 8-speed automatic, a torque-converter shudder felt through the seat at 35 to 50 mph under light throttle is a known issue. GM issued a TSB calling for a flush to the Dexron HP fluid spec, which has friction-modifier chemistry tuned to the 8L90 converter lockup behavior. The repair is well-documented and routinely successful.
Read more about The 8L90 8-speed torque-converter shudder fix
How the shudder presents
A repeatable vibration felt through the floor or seat, mostly in the lockup range between 35 and 50 mph at light cruise. Goes away briefly on harder throttle (which unlocks the converter) and returns on coast back into lockup. Easy to confuse with a driveline or tire issue; the scan tool and a road test isolate it.
What the fix involves
Drain and refill with Dexron HP fluid per the GM TSB procedure, usually a multi-fill flush to displace the old fluid completely. Post-flush road test to confirm the shudder is gone in the lockup range. The 8L90 itself is a durable transmission when the fluid is right; the fluid spec change is what matters.
04 of 05, 6.6L Duramax
6.6L Duramax diesel: why we refer it out
The 6.6L Duramax (LMM 2007 to 2010, LML 2011 to 2016, L5P 2017 and later) in the Sierra HD is one of the most capable diesel platforms on the road. We do not service it. Diesel engine, fuel-system, and emissions work goes to a dedicated diesel specialist, and we will point you to one. What follows is a plain-English rundown of the known service items so you know what you are dealing with.
Read more about 6.6L Duramax diesel: why we refer it out
CP4 fuel pump (LML, 2011 and later)
The Bosch CP4 high-pressure fuel pump on the LML has a documented failure pattern where internal wear sends metal debris through the entire fuel system. When the pump fails, the fuel rails, injectors, and lines all need to be cleaned or replaced. It is a heavy diesel fuel-system job, and CP3 conversion work alongside it, that belongs with a dedicated diesel specialist. We do not perform it, but we will point you to one.
DEF and DPF emissions service
The Diesel Exhaust Fluid heater, the Diesel Particulate Filter, and the EGR cooler are the three emissions-system items that come up most on the LML and L5P. These are diesel emissions repairs, which we do not perform. A dedicated diesel specialist handles them, and we will point you to one.
Allison 1000 transmission fluid
The Duramax pairs with the Allison 1000 6-speed automatic. Fluid exchange with Allison Transynd every 45,000 to 60,000 miles keeps the transmission alive past 250,000 miles. Because it lives behind the Duramax diesel, we send this work to the diesel specialist along with the rest of the truck rather than split the vehicle across two shops.
Tell us the year, make, model, and what you are noticing, and we will say what to check first.
05 of 05, How we
How we protect your GMC warranty
The federal Magnuson-Moss Warranty Act (15 U.S.C. section 2302) prohibits GM from voiding your warranty because routine maintenance was done at an independent shop. GM's published warranty terms acknowledge this. We document every service per GM standards and refer warranty-eligible items back to the dealer.
Read more about How we protect your GMC warranty
What we keep on file for you
Printed and digital service records that match the format GM expects. Parts receipts when we use OE-equivalent parts. If the dealer ever pushes back on a warranty claim, those documents are how Magnuson-Moss protections work in practice.
What we will not touch
Anything GM covers under active warranty (powertrain within the 5-year / 60,000-mile window, electric components within the 8-year / 100,000-mile window on the Hummer EV and Sierra EV, all current recall items) goes to the dealer. Independent shops that promise warranty work either are not telling the truth about what GM will honor or are billing for work the dealer would have done for free.
Call the shop or request an appointment and include the vehicle year, make, model, mileage, and symptoms.
FAQs
GMC service FAQs
Is GMC really just a rebadged Chevrolet?
For service purposes, yes. GMC is GM's professional-grade trim of Chevrolet platforms: Sierra is Silverado, Yukon is Tahoe, Yukon XL is Suburban, Acadia is Traverse, Canyon is Colorado, Terrain is Equinox. Same engines, same transmissions, same scan-tool protocol, same factory parts numbers. The Denali interior and trim package is what you pay extra for. The mechanical work is identical to the Chevrolet equivalent.
My Sierra has a tick on cold start. Is that the AFM lifter problem?
If you have a 2014 to 2019 Sierra 1500 or Yukon with the 5.3L L83 V8, or a Sierra Denali or Yukon Denali with the 6.2L L86, a cold-start tick that does not quiet up after a minute is almost certainly Active Fuel Management or Dynamic Fuel Management lifter collapse. Bring it in. Catching it before the lifter flattens a cam lobe is the difference between a lifter repair and an engine repair.
My Sierra shudders at 40 mph. What is that?
On a 2015 to 2019 Sierra, Yukon, Yukon XL, or Canyon with the GM 8L90 8-speed automatic, a shudder felt through the seat at 35 to 50 mph under light throttle is the documented torque-converter shudder. GM issued a TSB calling for a flush to Dexron HP fluid spec. The fix is straightforward and we do it routinely. Easy to confuse with a driveline or tire problem; the scan tool plus a road test confirms it.
Should I worry about the CP4 fuel pump on my Duramax?
If you have a 2011 or newer LML Duramax in your Sierra HD, yes, it is worth understanding. The Bosch CP4 has a documented failure pattern where internal wear sends metal debris through the entire fuel system. Catching it early is the difference between a pump replacement and a complete fuel-system job. We do not service the Duramax diesel, so the CP4 check, CP3 conversion, and any fuel-system work go to a dedicated diesel specialist, and we will point you to one.
My Acadia or Canyon has a cold-start rattle. Timing chain?
Likely. The 3.6L LFX and LFY V6 in the 2007 to 2016 Acadia and the 2015 to 2022 Canyon has a known timing chain stretch issue. A cold-start rattle from the front of the engine, often with VVT system codes following, is the typical pattern. Catching it before the chain skips teeth is critical; once it jumps timing, the repair scope grows significantly.
Will I lose my GMC warranty if I use Kneble's instead of the dealer?
No. The federal Magnuson-Moss Warranty Act prevents GM from voiding your warranty because routine maintenance was done at an independent shop. Keep every service record we hand you (printed receipt and digital copy), keep the parts receipts, and bring those to the dealer if they ever push back on a warranty claim. We document every service per GM standards.
What should I ask any independent shop before booking my GMC?
Three things. First, do they have a GM MDI2 or GDS2-class scan tool that reads GM-proprietary protocol (not just generic OBD-II). Second, will they give you a written estimate before any repair starts. Third, what happens if they find a warranty-eligible item or an active recall during the visit; the right answer is they hand it off to the dealer with documentation, not that they try to fix it themselves.
What does Kneble's do specifically about the Hummer EV and Sierra EV?
We service tires, brakes, suspension, cabin AC, and cabin electronics on the Hummer EV and Sierra EV at standard independent rates. We do not service the high-voltage battery pack (Ultium 200+ kWh on the Hummer EV, 800V architecture), the HV motor windings, the inverter, the DC fast-charge interface, or the battery cooling loop. Those items require the GMC dealer's factory permissions and tooling.
Further reading and viewing
Related Kneble's coverage for GMC and GM-platform owners
GMC-related and adjacent service content from the Kneble's library if you want to dig deeper.
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Local shop
Visit Kneble's in Mays Landing
5473 Somers Point Road, Mays Landing, NJ 08330
Five minutes off Route 40 between the Hamilton Mall and Lake Lenape. Ten minutes from the Atlantic City Expressway Exit 17. Twelve minutes from EHT and Northfield. Fifteen minutes from Somers Point along Mays Landing-Somers Point Road. From Folsom or Buena Vista, take 322 east, then south on Somers Point Road. Freddy J's Bar & Kitchen is nearby at 5698 Somers Point Road if you want to grab food before or after the appointment.
- Mon to Fri 8am to 5pm
- Saturday 8am to 4pm
- Sunday Closed
Reviews
Trusted by South Jersey drivers
Customers come to Kneble's for clear communication, practical recommendations, and repairs handled by a local team they can reach directly.
Friendly receptionist. In and out within 45 mins.
Janet Jackson, Google review
Service was performed quickly and the Kneble Team provided great communication throughout the visit.
Robert Orzechowski, Google review
Excellent quick service by personable staff and very qualified techs at a reasonable charge.
Glenn Peterson, Google review
Very good service here. Treated us very well. Great conversation with Carmen.
Gary Mazzone, Google review