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If you get under the trailer, at each corner you will see a curved metal conduit that conduit needs to be pulled back and 30W motor oil needs to be squirted into the conduit around the large spring that pushes on the corner to raise the roof.
Just remove the two screws and pull the conduit down...
Then squirt some oil into the conduit...
After you are done, push the conduit up and secure with the two bolts.
Now, under the trailer in the center is the track area where the cables go though, on the front and rear are two zerk grease fittings. Pump a lot of grease into each fitting. If this has never been done before, you will probably use an entire 14 oz tube of high pressure lithium grease or synthetic) for each fitting.
Rear pulley depends on the type. Older ones did require some lube, newer ones do not. I believe the main difference is the newer pulley has sealed bearings. (When I replaced the cable on my 2012 trailer, I asked if I should replace the rear adjustable pulley and the Goshen rep told me mine should have the newer model and I believe she said it has sealed bearings.)
If you have a powerwinch, under the winch motor on the trailer frame is a pan held in place by 4 screws. Remove those screws, drop the pan, and then spray a lube; I always used a dry lube, onto the drum and bottom of the gear assembly you will see when looking into it. Then replace the cover.
If a manual winch, chances are there is no cover to remove'; however, a spray of dry lube is still a good idea.
You should also have the axle bearing lubed too. You probably have the EZ lube or an AL-KO Ultra Lube system (basically identical), and can just pump grease into the zerk fittings until the old grease starts to come out the outer edge of the axle. MAKE SURE TO LIFT THE WHEEL AND SPIN IT WHILE PUMPING GREASE, AND USE A HAND PUMP DO NOT USE AN AIR OR POWER GREASE GUN.
(NOTE: Some will say to never do this and just manually repack the bearings every year. I did this for three years, then replaced the springs and brakes to a larger size and the seals had held and never leaked. But different strokes for different folks. So just noting this; how you do it is up to you.)