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Your Cruisemaster coupling lives at the hardest-working point of the whole trailer: every corrugation, water crossing, and dusty mile passes through it. The good news is that the DO35 and DO45 are designed to be serviced — greaseable bushes, a replaceable tow pin, and a locking mechanism you can inspect in thirty seconds. Here's the routine that keeps them articulating like new.
(Still choosing a coupling? Start with our DO35 vs DO45 comparison or the DO35 installation guide.)
The 30-second pre-tow check (every trip)
- Checklock dust cap test. The patented Checklock Gen.2 cap only fits when the two-stage lock is fully engaged. Cap won't seat? The coupling isn't locked — don't tow.
- Look at the pin. Glance at the tow pin for visible scoring, rust pitting, or a loose nut.
- Articulation feel. With the trailer hitched, the head should articulate without grinding or clunks.
Greasing schedule
Both couplings are fully greaseable through their nipples, and the acetal (DO45) or poly (DO35) bushes are what wear when grease runs dry.
- Highway use: grease every few months or per your service routine.
- After every serious off-road trip: corrugations hammer the bushes and dust works into everything — grease when you get home.
- After water crossings or beach towing: grease immediately. Fresh grease purges water and salt before corrosion starts.
Pump grease in until you see clean grease appear at the joints, wipe the excess (it attracts dust), and work the head through its articulation range to distribute it.
Annual inspection
- Bushes: with the coupling unhitched, check for play in the articulating head. Noticeable slop means the bushes are due — they're a serviceable wear item, which is the point of the design.
- Locking mechanism: cycle the two-stage Positive Interlock several times. It should be positive and spring back cleanly. Flush dust out with a suitable cleaner, then re-lubricate lightly.
- Mounting bolts: check the 4-bolt pattern torque against spec — corrugations loosen everything eventually.
- Reflective strip and webbing: replace if torn or faded; the rear support webbing matters if your coupling is mounted underside-of-drawbar.
The tow pin: your cheapest insurance
The tow pin is the sacrificial, replaceable heart of the system — and the one part you should never run to failure. Replace it when you see:
- Visible wear grooves or scoring where the coupling rides on the pin
- Rust pitting that doesn't clean off — pitting concentrates stress
- Any bend, however slight, after a hard hookup or jackknife event
- Unknown history — bought a used van or a second tow vehicle? Fit a fresh pin.
A spare pin kit in the tow vehicle also means a friend's truck or a rental vehicle can tow your trailer at short notice. Match the shaft to your coupling: the DO35 kit uses a 7/8″ (22mm) shaft, the DO45 kit a 1¼″ (32mm) shaft — check your tow tongue bore before ordering. Both kits include the pin, cover, and C-spanner.
FAQ
What grease should I use? A quality lithium-complex chassis grease is the standard choice; anything rated for exposed chassis points in wet conditions will serve.
My coupling squeaks over corrugations — is that bad? Usually it just means the bushes are dry. Grease first; if the squeak persists with fresh grease and you can feel play, budget for bushes.
Can I service it myself? Greasing, pin replacement, and inspection — absolutely, that's the design intent. Bush replacement is a bench job many owners do themselves; if in doubt, any trailer shop can do it quickly.
Keep a spare pin in the glovebox. DO35 and DO45 tow pin kits ship free with free 30-day returns — code RVSAFE10 takes 10% off your first order.