I have a square 3.5" jack on my trailer with a Bulldog motor. It does not have a 2 speed box but is direct drive.
Recently the electric motor moans and groans raising and lower the trailer. Disconnected the electric motor and it is very hard to crank manually too. Once the trailer is on the truck, everything spins freely, up and down full stroke.
Pulled the lower tube with screw and thought I would find a seized thrust bearing, I did not. It's got lots of grease and turns freely by hand.
However under the load of a few thousand pounds, could this bearing being dragging that severely?
Posted 2021-08-15 6:44 AM (#181638 - in reply to #181425) Subject: RE: Trailer Jack Thrust Bearing Issues?
Elite Veteran
Posts: 720
Don't know that I can help with the thrust bearing question, but do have 2 items- A) I seem to recall the service for a lot of those jacks was to remove the top plate and pour a cup of grease in. Literally, that was the manufacturer's recomendation. B) If the motor's elec wires are still hooked to the battery it will be hard to turn, as you are then acting as a generator. I tell folks to remove a wire if they have to hand crank- makes it much easier. You may do this to better get a feel of the drag.
Posted 2021-08-15 8:32 AM (#181662 - in reply to #181638) Subject: RE: Trailer Jack Thrust Bearing Issues?
Member
Posts: 5
Yes I finally disconnected the electric motor from the jack after spending hours thinking it was an electrical issue. The motor was drawing almost 50 amps when trying to raise the trailer.
But the hand crank is still VERY hard to crank up and somewhat hard to crank the trailer down. That's why I'm suspicious of the thrust bearing.
But the thrust bearing is full of grease. The ball bearings are visible and completely packed with grease. The bearing turns very freely by hand without any dragging or tight spots. I can't believe that when carrying the compression load of the trailer that this bearing is dragging so severely to cause this much drag. The Acme rod is fully greased and turns freely by hand and is not showing any signs of wear.
I was just hoping someone could confirm these bearings fail under compression load but otherwise appear normal when not under load.
Can't find a replacement locally so it will be several days until one arrives.
Trailer Jack Thrust Bearing Issues?
