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RV Review: Grand Design Momentum 397THS – big daddy rabbit toy hauler

Today’s review looks at one of the largest toy haulers I’ve seen, the Grand Design Momentum 397THS. One of the things I come across as I troll various RV-related forums is that a lot of folks don’t like toy haulers because they feel so utilitarian. While this toy hauler is absolutely huge, the interior portion of it feels every bit as nice as most nicer fifth wheels. 

And that’s just what this is—a relatively upscale fifth wheel with enough garage space to bring along almost anything that you might consider for the garage of a large fifth wheel. While your Shelby Cobra will not fit, most ATVs, side-by-sides or even a few Harleys will do just fine in that garage. 

Bring it

With almost two tons of cargo carrying capacity, none of those vehicles will be a problem for this. In fact, it’s not really what this rig can carry, but more what can carry this rig. 

With a gross weight of 20,000 pounds, you are well out of the single-axle pickup world and might really do well with something like a Heavy Duty Hauler. You know, something like the Volvo VNL—something along those lines. Before you disregard this idea, know that these trucks are actually pretty affordable when used, and half a million miles on one isn’t really a big deal. It may even be cheaper to buy a used semi tractor than it would be a used pickup in some cases. 

There are also groups who celebrate these types of RV tow vehicles. You could even do as some do and put something like a Smart car between the cab and the nose of the trailer. 

The Grand Design Momentum is very nice

But back to the trailer itself. Since this is a toy hauler, let’s look at the garage. Oftentimes the furnishings and upholstery in the garage of toy haulers definitely fit the definition of austere. That’s not true here. I thought the benches, with one on either side of the trailer, were actually pretty nice indeed. 

The garage in this trailer can fit up to a 13’ vehicle. So it almost could support an old VW Beetle. 

But there’s also a bed on a lift mechanism back here. The space is fully heated and cooled, of course. In fact, there are glass doors that cover the opening left by the cargo ramp. That means you can close off the outside world if you choose. 

That ramp also can become a patio, which is one of my favorite features of toy haulers. There are even steps included to get into the patio, but these are both an asset and a liability. There’s not a good place to put these when the ramp is closed unless you take up some space in the cargo area. 

Flushed with features

The back area also has its own bathroom. There’s not just a toilet, but a full bathroom with a shower and sink, as well. So, whether you’re bringing younger travelers or adults, this is a whole room that they have to themselves. 

Oddly, a glass door separates the garage area from the main living area. The reason I think this is odd is that, if you do have company, you can spy on them like they’re in a fish bowl. But then they can see when you wake up and head downstairs to make coffee. Of course, if it’s youngsters back there you can make sure they’re not killing one another, as well. 

Should you have adult company over and need a place for your own offspring, there is a bunk over the garage, sort of. It is a good place for one or two younger travelers, but could also serve as storage if you don’t have said youthful campers. 

One of the few downsides to this RV is up here there’s a light switch on the far side of the space. You know that junior’s going to jump up, head off to play with their friends and leave the lights on. One of you is going to have to climb up there and turn it off—because money and electricity do not grow on trees. 

Feeding frenzy

One of the biggest issues I normally see with toy haulers or many RVs designed for larger groups to enjoy is a kitchen that wouldn’t serve to handle meal prep for those larger groups. That’s not the case here. 

There’s a huge residential-sized oven with a four-burner propane cooktop. The microwave is of the convection variety and it, too, is substantial in size. There’s even proper dining space for six people, with four at a dining table that’s wall mounted and two at bar-height chairs that work with the island. 

There is no carpeting under the dining table nor in almost any of this trailer, except under the theater seating for some reason. 

Counter and storage space abound in this rig, as you might expect in a rig this huge. 

What’s up upstairs in the Grand Design Momentum

Upstairs Grand Design has a nice upper bathroom with a very deluxe shower head and plenty of space to accommodate what you came here to do, which could even include changing your clothes. 

A king or queen bed is available to you here. The closet in the nose of the trailer is really well thought out. Of course, there’s also a way to consume closet space with a washer and dryer, if you’d like. 

Keeping your cool

Grand Design has done a good job with the air conditioning system here. Each of the three roof-mounted air conditioners can operate on its own or as part of a system. Each unit also incorporates soft start technology as well as reduced energy consumption, so all three can run at the same time. But a nice thing is that you can run two of these units if you get to a site with 30-amp service.

Of course, if you’re off grid, the big generator aboard can run all three of them. That generator has its own gasoline tank and there’s a second tank to fuel motorized toys. This is neat because if you’re running something that uses other than just regular gasoline, such as something that runs on a gas-oil mixture or diesel fuel, you can still have gas for the generator. But if you do have gasoline in the tank with the pump, then you could literally fill your generator tank up, if that makes sense.

No matter where you camp you’re likely to be the awning champion with four awnings on this rig. That’s right. There’s one over the back patio and then three along the side of the trailer.

One thing this has which I can see as a really useful feature is lighting under the trailer. If you’re out in the desert at night it can get quite dark. So these lights would be great if you’re out there or need a beacon to find your way home if you’ve been on the ATVs all day. However, more likely, someone’s going to use these to light up their campground all. Night. Long. And be camped next to me in a developed campground. Don’t.

Summary

There’s a lot to like about this rig, whether you’re hauling toys or people. It’s one of the cases where the kitchen and bathrooms can actually support the cause. The bigger issue is finding camping spaces for this and even just hauling it around. But for those for whom this is an appropriate rig, I’m sure those details are just things to check off a list. 

I would love to read your comments and suggestions over on our new forums, where you can weigh in and start or join a discussion about all things RV. Here’s a link to my RV Reviews Forum.

Tony comes to RVtravel.com having worked at an RV dealership and been a lifelong RV enthusiast. He also has written the syndicated Curbside column about cars. You can find his writing here and at StressLessCamping where he also has a podcast about the RV life with his wife. 

These RV reviews are written based on information provided by the manufacturers along with our writer’s own research. We receive no money or other financial benefits from these reviews. They are intended only as a brief overview of the vehicle, not a comprehensive critique, which would require a thorough inspection and/or test drive.

Got an RV we need to look at? Contact us today and let us know in the form below – thank you!

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REVIEW OVERVIEW

Good use of front space
Light switch in upper bunk

SUMMARY

Grand Design's Momentum 397THS is a big, big toy hauler that's very nicely finished and has a lot of solid features.

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Scott Ellis
6 months ago

20k is well within the tow capacity of any current diesel dually.

Steve
6 months ago
Reply to  Scott Ellis

Minimum 3,000# of pin weight at GVWR (20,000 x 15%) + fifth wheel hitch weight + 4 passengers in a crew cab + everything else carried in the bed and cab = minimum 4500#+. And the trailer + dually are going to be nearly 65′ long. I wouldn’t want to tow that into any boondocking location here in the mountains of Colorado, even with a diesel dually 1-ton!

Steve
6 months ago

More. Dark. Gray. Ugh. Makes me want to scream at every RV interior designer at every manufacturer: “GRAY INTERIORS ARE DEPRESSING!” They have obviously never worked for a Federal government agency because then they would NEVER want to see another piece of gray furniture.

Actually this floorplan would make a unique couple’s fifth wheel with one major change. Leave the walk-in glass door into the garage, move the garage bunk bed over the rear bath and theater seats, chop off the garage, and move the garage ramp to just aft of the glass door. The garage ramp could be made much lighter because it would only hold people on a raised patio, not heavy “toys”. You might have to eliminate the rear shower due to the bunk bed, but it’s not needed for a young couple who can work remotely or retirees with an occasional grandkid in tow. But keep the generator. I estimate these changes would knock off at least 5-6K pounds of GVWR, which would put it well within the 1-ton dually range.

Roger Spalding
6 months ago

This rig is just way too big for my modest tastes. That doesn’t mean I don’t like it. Separate tank for generator is a great idea. I’ve seen vlogs in which some folks turn the garage into an enlarged living room, bed room or office. It really becomes a condo on wheels then. With such generous tank capacities, this 5thW looks ideal for dry camping. I wouldn’t want to stray too far out boondocking, because of increased inability to get back or get rescued if needed. You’d need a tank hauler if stuck in mud or sand. In general, I don’t care for GD products, especially where the absence of computer touch screen control panels is
concerned. But, this rig fills a need in the market place.

Tom H
6 months ago

I like the idea of a toy hauler and we looked at a lot of them when we were buying. My problem is the living/kitchen area. It may sound weird, but I prefer defined living spaces. I don’t like the couch or theater seating in the kitchen, literally on the other side of the island. I’m sure I’m not the only one. I’ve seen a couple that were divided but we liked our Solitude better. Just my thoughts…..

Jeff
1 month ago
Reply to  Tom H

Kinda hard to travel with your can am in the kitchen

Dave
6 months ago

Agree about your truck comments. Toy haulers are more about toys and sacrifice living space. My 37′ 5er is as long as I want to go, sometimes think it’s too big.

I think I’d rather have a Class A or C and tow a toy trailer.

RV Review: Grand Design Momentum 397THS – big daddy rabbit toy haulerGrand Design's Momentum 397THS is a big, big toy hauler that's very nicely finished and has a lot of solid features.