Does your Grand Cherokee have the side rails that run along the edges of the roof but not across? If yes - I recently bought this set of cross bars from amazon and an really happy with them. I also have a GC and they are the easiest and most secure cross bars I’ve ever installed.
We did the Medano Pass primitive road, which had a good bit of loose sand - we aired the tires down to 25 PSI and we fishtailed a few times. There's a big board in the visitor's center there at GSDNP that has the latest conditions on it - so I'd check that before going out. We couldn't make it to the top because the stream crossings were at 4 ft; a more adventurous type may have made it! As for tips, don't stop once you're in loose sand.
The roof rack is from Amazon, Brightline Roof Rack. Good luck!
Here is the Amazon link to them. Let me know if I can answer any questions. These fit the stock flush side rails perfectly on my 2014 summit.
BRIGHTLINES Crossbars Roof Racks Luggage Racks Replacement for 2011-2022 Jeep Grand Cherokee with Grooved Metal Roof Side Rails https://www.amazon.com/dp/B008RDL78G/ref=cm_sw_r_apan_i_08HYCJ4GYWW7NZXW37WY?_encoding=UTF8&psc=1
I have the BRIGHTLINES roof rack on Amazon and love it. Just took a 1,700 mile round trip road trip with a cargo basket attached to it with zero issues. Only $100 too.
Thanks! The crossbars are BRIGHTLINES Crossbars Roof Racks Luggage Racks Replacement for 2011-2021 Jeep Grand Cherokee https://www.amazon.com/dp/B008RDL78G/ref=cm_sw_r_cp_api_glc_fabc_KUP3Fb2026T0S, and the ski racks are Thule SnowPack Ski/Snowboard Rack, 6 Pair-Black https://www.amazon.com/dp/B07H4DCJ8M/ref=cm_sw_r_cp_api_glc_fabc_bi03FbBK4711B?psc=1.
I got the $100 ones from amazon. They are junk, and I have had to replace bits flying off of them (rubber strip, lock mechanism). But I looked at the factory mopar ones and I'm pretty sure they are exactly the same. https://www.amazon.com/gp/product/B008RDL78G/ref=oh_aui_search_asin_title?ie=UTF8&psc=1
BRIGHTLINES Crossbars Roof Racks... https://www.amazon.com/dp/B008RDL78G?ref=ppx_pop_mob_ap_share
I got these based on suggestions from this subreddit. They work just fine.
I bought these cheap ones and they have held up great so far. Held a rooftop tent and ski racks. 2018 Trailhawk
Something like this
They are from amazon. brightlines brand. They have worked great for a few years now.