Demco UMS Under-Bed 21K Autoslide Hijacker 8550037

Get short-bed fifth wheel towing for heavy rigs with the Demco Hijacker UMS Under-Bed 21K Autoslide (Part #8550037). Combining the convenience of an automatic 14" slider with the cleaner-bed advantage of under-bed mounting and serious 21,000 lb capacity, this hitch is built for big fifth wheels and toy haulers — with universal frame bracket compatibility for a wide range of trucks.

The Best of Both Worlds — Auto Slider + Clean Bed

This hitch combines two features that usually require choosing between them:

• Up to 14" of automatic travel using rack-and-pinion gear technology — for clean, easy navigation in tight spots without manual slider operation
• UMS (under-bed) mounting system — when the hitch is removed, your truck bed is completely free and clear for hauling other loads, with no bedrails in the way

Come rain or shine, the 21K Autoslide simply makes your life easier — which is what it's all about.

21,000 lb Capacity for Heavy Loads

The 8550037 is rated for 21,000 lbs of gross towing weight capacity, putting it in the right range for big fifth wheels, toy haulers, and heavy RV setups. Made in the USA with American steel and backed by a 5-year warranty.

Locked-In Connection — Wraparound Jaw with Locking Bar

The wraparound jaw with locking bar delivers a smoother, safer, and more secure connection to your king pin — cutting down on the rattle and trailer movement that wear on you over a long travel day.

Lower Profile, Lighter Weight

The 8550037 features a lower profile design and lighter weight than many comparable hitches, making installation and removal easier — important since the whole point of an under-bed system is being able to pull the hitch out when you need bed space. Easy access for routine maintenance is built in.

Adjustable Hitch Height for Level Towing

Three height settings let you fine-tune trailer height for level towing and proper bed rail clearance:

• Low: 15-1/2"
• Middle: 16-3/4"
• High: 18-1/4"

Standard Pin Boxes Activate the Slide Automatically

For most setups, no locking plate is required to activate the slide mechanism — standard pin boxes do the job out of the box.

⚠️ Cushioned Pin Box Requirement

A capture plate is required for the slide mechanism to activate with the following cushioned pin boxes:

• MOR/ryde
• Trailair Tri Glide
• 5th Airborne (Standard or Extended)
• Demco Glide Ride

Considering Other Demco Hitches?

We carry related Demco fifth wheel hitches for different truck setups and capacity needs:

• Demco UMS Under-Bed 18K Autoslide (8550022) — same under-bed Autoslide platform with 18K capacity for lighter rigs
• Demco 21K Ford Prep Package Autoslide (8550038) — same 21K under-bed Autoslide, drops directly into factory Ford pucks
• Demco Hijacker 21K Autoslide (8550035) — same 21K Autoslide capacity with above-bed rail mounting (rails sold separately)
• Demco 21K Autoslide above-bed WITH rails (8550036) — same 21K above-bed Autoslide with bed rails included
• Demco Autoslide 18K above-bed (8550034) — same Autoslide platform with 18K capacity and above-bed rail mount
• Demco Hijacker SL 21K Underbox (8550033) — same 21K capacity, fixed mount (no slider), for long-box trucks

What's Included (and What's Not)

Included: Hitch

Sold separately:

• Vehicle-specific UMS frame brackets — required for installation
• Capture plate — required only if you have one of the cushioned pin boxes listed above

Key Features

• 14" automatic slider using rack-and-pinion gear technology
• UMS under-bed mounting — leaves truck bed free and clear when hitch is removed
• 21,000 lb capacity
• Wraparound jaw with locking bar
• 3 vertical height adjustments (15-1/2", 16-3/4", 18-1/4")
• Lower profile, lighter weight
• Easy access for routine maintenance
• No locking plate required for standard pin boxes
• Made in USA with American steel
• FREE freight shipping to the 48 states (freight items are not returnable)
• Backed by a 5-year warranty

Specifications

• Brand: Demco
• Model: Hijacker UMS Under-Bed 21K Autoslide
• Part Number: 8550037
• Type: Slider Fifth Wheel Hitch (for short truck beds)
• Capacity: 21,000 lb
• Slider Travel: Up to 14" (automatic, rack-and-pinion)
• Rail Type: Demco UMS under-bed
• Hitch Heights: 15-1/2" / 16-3/4" / 18-1/4"
• Material: American steel
• Includes: Hitch only
• Sold Separately: Vehicle-specific UMS frame brackets; capture plate (if needed for cushioned pin boxes)
• Cushioned Pin Box Requirement: Capture plate required for MOR/ryde, Trailair Tri Glide, 5th Airborne (Standard/Extended), Demco Glide Ride
• Country of Origin: USA
• Warranty: 5-year