Hey Guys, Looking to get some advice here. I have a 95' 312 (S/N:7DK05146 which is equivalent to the 6GK00393 and up) and I'm loosing oil from my swing motor drive into my swing bearing. I started noticing oil/grease mix leaking around the swing bearing seal onto the frame. It doesn't take long to empty the gearbox once filled up. I've had no loss of hydraulic oil so I know oil isn't leaking from the swing motor down into the gearbox. I know I need to pull the swing motor, but which seal would be the most likely culprit? I'm thinking it would be item #13 on the diagram I attached. Assuming 13 is the culprit, I'll have to pull the gear and bottom housing off to change the seal. Whose done it and how hard is it? Obviously I have oil mixed in with the swing bearing, with that said, is there anything that should be done to the swing bearing besides greasing it well once the swing drive seal is replaced and filled with oil? Thanks for the help!
I just did mine. Hitachi EX60. Wasn't too difficult. You'll need a press for the bearings and a hoist or machine to lift it out. Mine was the bottom seal. All torn up. I polished the surface it seals against and it's holding up well. The worst part was cleaning out the muck from the turn table. The previous owner was using grease and Slick 50 to keep it lubed. It was lubricated well but what a mess.
No 13 is the one you need to change. There's a cover plate with 4 bolts that can be removed so you can scoop or suck the old grease and oil mix out of the swing gear bowl, It is located near the front close to the boom cylinder brackets. then you add new fresh grease, add enough so the the pinion pushes a small wave in front of it when swinging. Also pump fresh grease into the bearing while slowly swinging until you see fresh grease escaping but be careful so the outer seal isn't pushed out of it's groove.
That seal position is a design flaw in all excavators. All the wear material from the gears drops onto that seal and just sits there becoming lapping compound. Changing the oil in a timely manner makes the seal last longer but they all eventually start leaking. As I recall on the Cat units, the pinion and shaft are all one piece so you have to press the shaft out of the bearing in order to get to the seal. The bearing is usually a double cone unit that takes lots of tons of force to press the shaft out. I've seen a few of the gear cases broke trying to push the shaft out of the bearing. Hopefully since your unit is pretty small it won't be that tough. When you get the shaft out of the bearing, check the seal riding area pretty carefully. Most of the shafts will need a speedy sleeve to cover up the worn area. Good Luck!
Good day I suggest you explore the reason for seal failure, has the pinion shaft bearing any movement it can be that the swing ring bearing is causing the bearing to fail. It would be pointless to pull the transmission only to end up with the same problem later. Kind regards Uffex
Here's the procedure to R&I the swing drive plus D&A once you have it out. This is from a 6GK-prefix machine which is supposed to be the same as your 7DK offering. There may be detail differences but the general procedure should work. Also the instructions regarding the swing gear greasing once you have the grease bath cleaned out. One useful titbit is that it gives the approximate total grease capacity of the compartment.
Hey guys, thanks for all the replies. I picked this excavator up this past spring and have used it very little due to the leak. Finally finding the time to get it fixed. I'll definitely clean out the swing bearing pan and renew with grease. What type of grease would you recommend putting back in it? Nige, thanks for the procedure. Looks a little more in depth for the tools I have in my shop, no bearing press. I'll most likely take it to a shop and have them change the seal out while checking over the whole swing drive. Bearings are pretty cheap to install if it's already apart. A lot cheaper than the used prices for swing drives I found online.
The manual quotes an EP-2 multipurpose grease for that application.
Hey guys, one more quick question on this thread. My swing motor just got rebuilt. I'm going to install sometime next week. Can anyone give me the torque value on the 12 bolts that hold the gearbox to the swing drive housing?
if you mean these ones they are listed as M12. Torque for an M12 is 75 +/- 15 ft lbs.
Hey nige, I saw those ones for bolting the motor to the gearbox. I need the lower ones that bolt the actually gearbox to the main frame.
Those are M16. Tighten them to 175 +/- 30 ft lbs.
Hi guys, Question regarding the swing motor. When I got my EX60 a few years ago for developing my small property, the swing motor oil wold leak in a day or two. I took my fathers advice and just loaded it with grease. It seems ok, even after a few years of limited use. I am going to start a bigger project and will be using my machine full time for a few months. Could I end up with any major problems with the grease or should I try to replace the seal and fill back with oil? Second question is my bucket main pin never had a grease fitting and was quite sloppy when I got it. I think it is problably past a new bushing and pin. Can you get a whole new stick end and weld it on? Or do yo have to purchase an entire stick. Thanks for any help, I am a drywaller by trade but love playing with my machine. Cheers, Colin.
Regarding your swing motor it would be better long-term to have oil in it rather than grease. The bucket pin joint on the stick could always be built up and line bored back to size. Probably the cheapest option, and you have the advantage that on your machine the stick is small enough to be able to remove it completely and take it to a machine shop to have it rebored.