On Tuesday, May 15, 2018 at 2:22:48 PM UTC-4, Bob Kuykendall wrote:
I would run, not walk, away from the proposed deal. Have the wheel bearings replaced and carry on.

Agreed. I believe the bearings in that trailer are serviceable and easily replaceable (later ones are sealed for life). In my experience, the stuff that goes wrong includes:

1. If the brakes are not adjusted periodically and/or the lining wears down too much, they can stick in the "on" position after a vigorous stop.
2. The surge mechanism can bind from corrosion, preventing the brakes from being applied or, after a hard stop, not releasing.
3. The damper in the surge brake can wear, causing the trailer brakes to be applied too harshly (you can feel and hear the trailer axle hopping off the ground when the brakes are applied quickly).
4. The tongue can break from fatigue.
5. The front mount where the tube is attached to the front cross member of the chassis and into which the tongue is inserted can break from fatigue.
6. The brackets where the axle is mounted to the steel tube rails of the trailer can fatigue and fracture, allowing the axle to begin pushing the floor up.
7. When/if bearings fail and/or the brakes are stuck in the "on" position, the hub can get very hot, causing the brake drum to develop a small crack in the thickest part where the bearings are mounted.
8. The rubber torsion spring/mount in the axle can fail, allowing the trailer to settle on the axle and reducing or eliminating the spring effect

I've seen/experienced the first 7 and heard about the 8th. There are more failure modes, I'm sure.

That said, I agree I'd just repack the bearings (replace if needed), inspect the brake shoes and drums, adjust, check the tongue/surge mechanism and adjust if necessary, check the tongue and mounting for cracks, and drive on.

There are hydraulic trailer surge brake systems with manual/cable-actuated parking brakes, however, and I'd look there before looking at electric brakes.

Chip Bearden