What is the Difference Between Demo Autoslide # DM39SV and # DM29GV for 2026 GMC?

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Question:

Hello, I have a couple of questions regarding the best 5th wheel hitch for my Grand design 150 reflection series with curt helix pin box. I will be pulling the 5th wheel with a 2026 GMC Sierra 3500. My plan is to purchase either of these two Demco autosliding - 1. Part Number: DM39SV 2. Part Number: DM29GV Are there any major differences between the 2 of them? Does DM39SV have any advantage over the 29GV? Do i need any additional parts for the curt helix pin since this a suspension pin box? box to work with either of the 2? Thank you!

asked by: Femi A

0

Expert Reply:

Hello Femi,

Thanks for reaching out! Both the Demco Autoslide # DM39SV and # DM29GV are excellent choices for your 2026 GMC Sierra 3500 with the factory prep package, and both are compatible with your Grand Design Reflection 150 Series.

The biggest difference between the two is how they mount in the truck. The # DM29GV mounts directly into the factory Chevrolet/GMC puck system, making it the cleaner and more straightforward installation. The # DM39SV mounts to an adapter (please see attached image) that locks into the factory puck system, allowing the hitch to attach like a traditional above-bed rail hitch.

Other than the mounting style, both hitches offer the same 21,000 lb towing capacity, 14 inches of automatic slide travel, and the same single-jaw design. Unless you specifically want the rail-style adapter setup, I would recommend the # DM29GV for its simpler, direct-to-puck installation.

For your Curt Helux pin box, you will also need the Demco Autoslide Locking Plate for Lippert Helux Pin Boxes # DM53KV. This locking plate is required for the Autoslide to function properly by preventing the king pin from rotating in the hitch.

If it were my truck, I'd go with the # DM29GV along with the # DM53KV locking plate. It gives you a clean OEM installation while providing all the same towing and autoslide features as the # DM39SV.

Is this your first 5th wheel, or just getting a new truck and deciding to do a 5th wheel hitch upgrade?

expert reply by: Kate F

0

Demco Adapter Plate
(click to enlarge)

Femi A.

7/9/2026

Thank you! This is super helpful. This is my first 5th wheel and HD truck. Will go ahead and purchase DM29GV along with the # DM53KV locking plate.

Kate F.

7/13/2026

@FemiA My pleasure Femi! Congrats on the first 5th wheel, very exciting!

Answer 1

Hey George, thanks for reaching out! The Demco Autosliding Hijacker is one of my favorites when it comes to 5th wheel hitches. When did you pick it up? Have you inspected the gear system yet? There is a snippet from the instructions (see attached…

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Answer 2

The silver capture plates on the Demco Hijacker Autoslide Hitch #DM8550034 should be adjusted after you hitch the trailer. You want to push the capture plates against both sides of the pin box then finger-tighten the inside jam nuts against the…

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Answer 3

The OEM prep package consists of 4 "pucks" in the bed of the truck that will allow you to drop in puck style hitches for easy installation and removal, that gives you a completely clear bed when not in use. The B&W Companion OEM 5th…

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Answer 4

Hello Femi, Thanks for reaching out! Both the Demco Autoslide #DM39SV and #DM29GV are excellent choices for your 2026 GMC Sierra 3500 with the factory prep package, and both are compatible with your Grand Design Reflection 150 Series. The biggest…

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Answer 5

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Answer 6

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Answer 7

A 4-Way trailer connector has the basic lighting functions only; running lights, left turn signal and brake lights, right turn signal and brake lights, and ground. A 7-Way has these functions and a 12 volt circuit, a circuit for electric trailer…

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Answer 8

In order to determine the torque rating for the lug nuts on your trailer you will need to know check out the chart I attached that shows all of the torque specs for all the trailer lugs available based on stud size, wheel material and wheel size.

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Answer 9

Yes, it will work. You'll just need to cut the Lance 6-pin connector out and rewire it into the etrailer Trailer Wiring 7-Way Upgrade Kit w/ Junction Box and RV Style Connector item #e99011. Here are the individual functions of that Lance 6-pin:…

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Answer 10

You will have to go with a sliding hitch to allow the trailer to make tight turns. For a trailer 8 feet wide the only bed length that's going to allow 90 degree turns without a slider is a stationary hitch. That being said you have two options.…

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Answer 11

Hey Jerry, GM moved the placement of their puck systems starting with 2020 models so you are correct that the pucks would have the hitch not sit directly over the axle. GM did the math and made sure that this placement wouldn't adversely affect…

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Answer 12

Hey Jeff! The MORryde GooseTech 5th Wheel to Gooseneck Pin Box #MR97MV comes with a Demco eZ-Latch. The best option for a lock is the InfiniteRule Lock for Cast Demco eZ-Latch Trailer Couplers #IR66FR. This is designed to for a standard coupler but…

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What is the Difference Between Demo Autoslide # DM39SV and # DM29GV for 2026 GMC?

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