We own a 2021 Grand Design Momentum 393g toy hauler that has severe frame flex and bolts in slide have started backing out. We noticed this when driving and the extreme pushing/chucking when accelerating or braking and also the visible failure on the unit. We have contacted Gran Design, the manufacturer, for warranty repair and was able to go see the unit when they torn down to look at frame. The side walls were both broken and wall frame fell out when opened up. The unit is now at the manufacturer in Indiana for repair, my husband did not feel it was safe to tow so we requested manufacturer transport the unit. We were told by a Lippert Frame Tech the unit is not safe to use.
2021 Grand Design Momentum body problems
42 complaints (72% of all complaints for this car).
- owner complaints
- 42
- of this car's complaints
- 72%
- crashes
- 0
- recalls
- 0
Which part fails
- Body24
- Frame and members4
At what mileage
Complaints by mileage at the time of the problem.
0k-25k
25k-50k
50k-75k
75k-100k
100k-125k
125k-150k
150k-175k
175k-200k
200k+
Grand Design Momentum body problems in other years
Related recalls
No recalls on record for this model year.
Related investigations
Frame Flex on Grand Design Fifth Wheel Recreational Trailers
The Office of Defects Investigation (ODI) has received twenty-three complaints alleging excessive frame flex on model year 2017-2023 Grand Design fifth wheel recreational trailers, models Momentum and Solitude. Twenty-two of the complaints allege that excessive frame flex resulted in a cargo or entry door opening while in transit, some with objects lost on roadways, while six complaints also state that slideouts extended out partially. ODI has been in contact with both Grand Design and Lippert, the frame manufacturer. Grand Design believes that some frame flex, generally considered to be vertical movement in the upper deck area of the fifth wheel, is normal. However, Grand Design has developed a technical service bulletin (TSB), to evaluate concerns of excessive frame flex, defined as vertical movement greater than 3/8 inch. Per Grand Design, the frame flex is only occurring in the upper deck area of the fifth wheel and is resulting in cosmetic defects such as moving sidewalls, damage to cabinets, binding doors, etc. However, Lippert believes that the effects of frame flex may also extend back to the front axle of the trailer.While Lippert provides frames for multiple trailer manufacturers, the majority of complaints are for these Grand Design products. Cargo and entry doors that open and slideouts that extend while in transit increase the risk of injury or a crash. ODI is opening this Preliminary Evaluation (PE) to evaluate the severity of the potential problem and to determine whether an unreasonable risk to motor vehicle safety exists. To review the ODI reports cited in the Opening Resume ODI Report Identification Number document, go to
PE24029
What 2021 Grand Design Momentum owners say
Most recent owner complaints, unedited.
I am reporting a serious, progressive structural defect involving excessive frame flex and structural failure on a 2021 Grand Design Momentum 395MS fifth-wheel RV. This complaint directly aligns with the ongoing the federal safety agency investigation PE24-0209. The unit exhibits clear and worsening structural integrity failure, including: Slideouts and doors open during transport. Upper deck walls moving under load Lag bolts missing or backing out and pushing through flooring At least one critical structural bolt missing from factory installation Floor deformation and slope changes in the upper deck Slide-out malfunction due to frame distortion Loud popping and snapping noises while towing consistent with frame flex or structural separation These conditions reflect loss of structural integrity under normal use and represent a serious safety hazard, including risk of catastrophic failure while towing. On June 24, 2026, Lippert (frame/component supplier) assigned Case #6876203 and scheduled a mobile service inspection. This Grand Design Momentum 395ms is not safe to tow. It is a danger on the roads and they need to be recalled at the least for inspections of the frame for damage.
Frame cracked and suspension issues.
Regarding 2021 Grand Design Momentum 376THS: Compartment doors popping open during transport; Grand Design Customer Satisfaction Campaign TSB-24-001 dated 11/1/2025 regarding frame flex and wall securement. Returned to dealer on 12/1/2025 for inspection. Dealer found the following: All doors except p/s compartment door warped or bowed; P/S cracking in sidewall paneling on slides Front cap mollding broken screws Deformation or cracks at expansion joint located under upper deck slide out Gapping between exterior wall and floor Screw cover separation around front bulkhead Loose or shifted wall panel trim; trim pulled away from floor Crinkling wallpaper and cabinet paneling loos in upper cabinets
Scheduled appointment with dealer for the Grand Design Frame Flex recall today, 22 May 2026. Approximately 4 hours after dropping the trailer off the dealer called and said that the technician found significant frame flex and that the unit was unsafe to be towed. No other information was provided. I did ask for the measurements that the TSB 24-001 requires to be filled out ans submitted to Grand Design. The lady that called was completely unaware of what I was asking for.
My Grand Design Momentum fifth wheel trailer is experiencing frame flex and structural integrity failure. The unit has developed spider cracking in the exterior fiberglass, interior wall separation, and plumbing issues believed to be caused by frame flex. The dealership has acknowledged structural concerns and installed lag bolts, but the underlying structural defect remains. Grand Design has denied that the frame flex caused the structural damage. This creates a serious safety risk while towing, including potential structural failure. I believe this is a manufacturing defect affecting the structural frame integrity.
The contact owns a 2021 Grand Design Momentum RV. The contact stated that while inspecting the RV, the contact became aware that the outrigger brackets were bent and fractured. The contact stated that the failure was visible over the axles. In addition, the welding on the cross-member beams was fractured, causing the floor to crack, and the exterior fiberglass was cracked by the bedroom slide-out. Additionally, there was a four-inch-long crack on the frame of the upper deck. Most recently, the contact found movement of the cabinets in the upper deck, and a portion of the fiberglass on the front cap had separated from the roof. The RV was taken to a welding shop to be diagnosed, and it was determined that the metal used to support the walls in the unit was not strong enough. The contact was informed that the weight on top caused it to bend and crack. The outrigger brackets were replaced, the cross members were replaced, and the other cracks were repaired. The manufacturer was notified of the failure and denied the warranty claim. However, the manufacturer failed to acknowledge the failure and advised the contact to call the insurance company since the manufacturer believed that the RV had been involved in an accident. The contact denied that the RV had been in an accident. The contact noticed the issues since the RV was purchased. The failure mileage was unknown.
The contact owns a 2021 Grand Design Recreational Momentum RV. The contact stated while driving 55 MPH, the RV frame flexed. The contact stated that when the RV was loaded, the failure persisted. The contact stated that the screws to the bedroom slide out were detaching. Neither an RV dealer nor an independent mechanic was contacted. The vehicle was not taken to a dealer or an independent mechanic to be diagnosed. The vehicle was not repaired. The manufacturer was notified of the failure and informed the contact to bring the RV to a technician to be inspected. The failure mileage was 15,000.
excessive frame flex/failure, Interior cabinetry coming cracked and apart. Floor separating from side walls. Main door coming open during transit.
The contact owns a 2021 Grand Design Momentum RV. The contact stated while the RV was parked and occupied, or while driving the RV, there was an abnormal popping and creaking sound coming from the frame of the RV while depressing accelerator pedal or depressing the brake pedal. Neither a dealer nor an independent mechanic was contacted. The contact stated that while driving the RV at an undisclosed speed, the doors opened independently. Additionally, while walking inside the RV, there was an abnormal sound coming from the floorboards. The contact also stated that the frame of the RV was full of rust. The vehicle was not taken to a dealer or independent mechanic to be diagnosed or repaired. The manufacturer was not notified of the failures. The failure mileage was 6,000.
Questions about the 2021 Grand Design Momentum body
Does the 2021 Grand Design Momentum have body problems?
Owners have filed 42 complaints about the body of the 2021 Grand Design Momentum, 72% of all its complaints, more than any other problem.
At what mileage do 2021 Grand Design Momentum body problems start?
Not enough complaints include the mileage to tell.
Was there a recall on the 2021 Grand Design Momentum body?
There is no recall for this problem on this model year.
What year does the Grand Design Momentum have the most body problems?
The Grand Design Momentum model years with the most body complaints are 2021 (42 complaints), 2022 (28 complaints) and 2023 (20 complaints).
Other 2021 Grand Design Momentum problems
Suspension 19Locks 9Brakes 2Electrical 1Lights 1Transmission 1
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