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Hydrastar Demco 3.5K Axles, 5 Lug Integral Tandem Axle Trailer Disc Brake Kit-Complete (1/2")

Hydrastar® Demco 3.5K Axles, 5 Lug Integral Tandem Axle Trailer Disc Brake Kit-Complete (1/2") {#S7KMH3-T1}

SKU #S7KMH3-T1
by Hydrastar
Save 19% Save 19%
$1,350.00
$1,350.00 - $1,350.00
$1,350.00
$1,099.00
$1,099.00 - $1,099.00
$1,099.00

Complete tandem axle disc brake conversion kit for 3.5K axles with 5-lug hubs. Includes the Demco DA70 7,000 lb surge brake actuator with 2" ball coupler, Hydrastar 3.5K Dacromet-coated disc brake assemblies, hydraulic brake lines, and all stainless mounting hardware needed for a full conversion.

3 YEAR Limited Warranty— on Disc Brakes
3.5K
Axle Rating
TANDEM
Axle
DISC
Brakes
DOT
Compliant
What You Get

In The Box & Sold Separately

Included
✓
(2) E303-3K1-A — Hydrastar ® 3.5K Rated, Dacromet Coated Integral Single Axle Brake Kit (1/2 in. )
✓
(4) L68149 — Hydrastar® 3.5K Rated Inner Bearing
✓
(4) L44649 — Hydrastar® 3.5K Rated Outer Bearing
✓
(4) MAT-GS-10-172 — Hydrastar® 3.5K Rated Grease Seal
✓
(4) MAT-20-200L — Press Posi Lube Grease Gap
✓
(20) L-122076 — 1/2-20" Coned Open End Lug Nuts
✓
(1) DM87075101
✓
(2) HWK-3KS Stainless Steel Axle Mounting Hardware Kits
✓
(4) 3.5K Axle Rated Integral 5 Lug Dacromet Coated Rotor
✓
(4) 3.5k Axle Rated Zinc Calipers
✓
(4) 3.5k Axle Mounting Brackets w/Stainless Mounting Hardware
✓
Complete Surge Brake Actuator Kit for Tandem Axle Trailers, Includes:
Sold Separately
–
DOT 3 or DOT 4 Brake Fluid
–
Tools for installation
What You Need to Know

Key Features & Specs

EOH Actuator
  • ✓4 ft of wire length to customize any job
Disc Brake Kit
  • ✓Dacromet Coated Rotor and Bracket for industry-standard performance
  • ✓3 Year Limited Warranty on Hydrastar Disc Brakes
Compliance & Certifications
  • ✓Meets SAE J1650 Standards (0.028 in.)
Questions about fitment?

Feel free to reach out to us or start a live chat in the bottom right corner for assistance.

Additional Details

Specifications & Compliance

•
2" Ball Coupler w/ Demco EZ Latch Coupler (Autolocking)
•
Reverse Lock Out Solenoid, DISC Brake Ready
•
Requires a 5 Flat Harness (Included)
•
Stainless Mounting Hardware Included: 1/2" X 5" Stainless Bolts (3), 1/2-13" Nylon Lock Nuts (3), Flat Washers (6)
•
Required use of D.O.T. 3 or 4 Brake Fluid. (Not included.)
•
Corrosion-resistant Dacromet Coated Rotor and Bracket for Industry Standard trusted performance.
•
Premium, corrosion-resistant Dacromet Coated Caliper construction for reliable performance.
•
1/2" in. wheel studs
•
The Hydrastar® Brake Line Kit includes: – DOT Approved Rubber Flexible Brake Lines
•
BH-288" (1), BH-80" (2), BH-24" (3), BH-36" (1), BH-T-3FIF (3) – Brass T Fittings
•
This KIT also includes all Bearings, Grease Seals, and Grease Caps
•
(1) JM-6525WH 5Way Flat, Dual Full Length Grounds, 35' Light Wire Harness
Common Questions

Before You Buy

What PSI actuator is included?+
The 1,600 PSI GEN 8 actuator is included. This is the correct pressure for both disc and drum brake applications.
Do I need anything else to complete the install?+
You will need DOT 3 brake fluid (not included). Basic hand tools and a way to mount the actuator to your trailer tongue.
What is the difference between integral and slip over?+
Integral kits replace your entire hub and rotor as one piece. Slip over kits mount the rotor over your existing hub — faster install, no hub removal needed.
2024–2026 GM Truck & SUV Owners

Dashboard showing “Service Trailer Brakes”? Brakes disabled?

Affects Silverado, Sierra, Tahoe, Suburban, Yukon, Escalade, Colorado, Canyon & Hummer EV with integrated trailer brake controller.

That’s a known GM compatibility issue across the 2024–2026 lineup. Hydrastar has the fix — the GM Diode Module (#381-7074) is a plug-and-play inline solution.

New Ford Truck Owners

Connectivity issues before or after the dealer flash? Brakes dropping in and out?

Affects new Ford trucks when switching from electric mode to EOH mode.

Our Hydrastar Controller Adapter Module (#381-7073) has been very successful resolving this for Ford owners. Note: this is not a Hydrastar issue — just a Hydrastar part that helps.

Need Help Choosing?
Our team has helped thousands of trailer owners find the right setup.
Fastest response? Use the chat bubble in the bottom-right corner ↘
or call (812) 655-4544 · Mon–Fri, 8am–4:30pm ET