How to Determine Correct Gen-Y Gooseneck For Grand Design Momentum 399TH-R

Published 03/22/2024

Question:

What Gen y gooseneck hitch would I need to replace my 2021 Grand Design momentum 399TH-R toy hauler?

asked by: Jason C

Expert Reply:

Hi there Jason; I took a look but apart from seeing it was a MORryde, was unable to find the model of the pin box currently on your 2021 Grand Design Momentum 399TH-R, but it's still possible to find by taking a few measurements of the bolt pattern. I have added a link below to a help article called "4 Steps to Choosing Your 5th Wheel Pin Box" and if you scroll down a bit in the article, it walks you through the measurements that are needed.

The Lippert 1621 bolt pattern is the most common, so it wouldn't surprise me if that's what you had. But you'll want to verify, and after doing so, find the Gen-Y with the right capacities. For example, with the weight and pin weight of your rig, if you did have the 1621 bolt pattern you would want the Gen-Y Hitch Shock Absorbing 5th Wheel to Gooseneck Pin Box # GY66FR.

This has a 30,000 lb capacity but more importantly is for pin weights between 3,500 lbs and 5,500 lbs, which yours will fall into, and that's what you want to go by for the best ride. I have added a link below to our entire selection of Gen-Y 5th wheel to gooseneck adapters for you to go through once you find the bolt pattern.

expert reply by: Kyle S