Hi all,
That's my latest repair to share with you. Fiat 355M crawler tractor it's a 45hp track type tractor with dimensions of 150cm width and 3 m length. Weight 2300 kgs. Very robust.
It's lifting mechanism it's an autonomous system and hold something like 7 ltr of hydraulic oil.
Drain oil from the system. Remove also oil filter.
Remove the whole unit from the tractor
remove the front cover of the unit and the rear cover.
Remove with a puller the two lifting arms from the main shaft, and knock shaft with a soft hummer from right to left (shaft is of two diameter; left side is bigger in diameter than right side). While removing main shaft, hold the unit that attaching piston and turning the main shaft upwards. while these removed, knock the piston with the handle of a hummer in order to be removed from the front side (at this point piston is closer to front side so less travel). Then knock out the piston liner (liner had no signs of damage but it was cheap so i replace it)
On the main body of the lifting device where the main shaft rotates there are two bronze bushings in each side. Right side is less diameter than left side. To remove them you pass through a full threaded shaft of 40 cm length and 20 mm diameter half way in the unit's body. Then you machine a round plate on a lathe equal to the outer diameter of the bronze sleeves, with a hole in the center equal to the diameter of the shaft you are using. You screw a nut at the end weld it on (the shaft). welded screw is located halfway in the unit. At the other end you pass shaft through a pipe which is slightly bigger of the outer diameter of bronze bushings. With a flat piece metal of 10 mm thickness cover the end of tube and let full thread shaft to pass through. Always center it. Screw a nut till parts start to tighten. Make sure that all are in a straight line. Keep screwing. Will notice that the inner bronze sleeve contacts the outer sleeve and are coming outwards and removed (sleeves have something like 4 cm distance from each other on both sides)
In the same way you remove the left side.
Now to install new bushings you are using same puller. You just place them free one inside of unit and one outside. you place the puller through them, lubricate them, center them and start screwing till they reach their position. MAKE SURE YOU NOTICE WHERE THE INSIDE SLEEVE STOPS!
Same way you place the other end.
Then you install the liner. Lubricate the inner wall. Carefully place the seal on the piston along with scrapers (lubricate them)
Using a piston drive tool, install the piston in the liner (direction: from front side) till the top of the piston comes same level with sleeve edge (top). At this point you place the front cover.
Then place the piston rod and holder in the center of unit and pass the main shaft from left to right through holder making sure that you align marks.
Then you place one sealing ring on the right and left right of main shaft. It's important to lubricate these with oil. On the right side there is also a metal support ring which is between sealing ring and lifting arm. On the left side there is no support due to limited space.
Make sure to connect the lifting control lever on the piston rod holder.
Place the rear cover and oil filter.
Put unit on the tractor, connect lines, fill the system with oil and you are finished...
Good luck to ones will try this...
Below some photos taken