2021 Grand Design Momentum structure problems

42 owner complaints filed with NHTSA name the structure on the 2021 Grand Design Momentum — 75% of all complaints for this model year.

Structure complaints

75%

share of all complaints

—

median reported incident mileage

0 / 0

crash / fire reports

What owners report

“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…”
filed Jul 14, 2026
“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 NHTSA investigation PE24-0209. The unit exhibits clear and worsening structural…”
filed Jul 8, 2026
“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…”
filed May 24, 2026

Verbatim excerpts from complaints filed with NHTSA. Reports are not independently verified.

Grand Design is addressing concerns of excessive frame flex or wall securement in the front upper deck area of a limited number of fifth-wheel units. This condition could potentially occur over time due to a combination…
920017 · Service Campaign · issued Nov 22, 2025
TSB 24-001 Issued in March on March 7th. Concern: Complaint of upper deck flex which results in cosmetic damages to the interior and excessive flex at the pin box. Remedy : The procedure outlined in attached summary to…
TSB 24-001 · Service Bulletin/Repair Instructions · issued Apr 10, 2024