Help! JD 8A backhoe hyd. cylinder repair

[gthawus]

Hi! I'm attempting to install a new seal kit in the dipper hydraulic cylinder of my 8A backhoe. I've got the rod removed from the cylinder (loosening the end cap was a real chore!). Now, the piston won't slide off the rod end (see attached pic). It will move about 1/4" then meets strong resistance. I've tried lightly using a puller with no luck. Don't want to use too much force at this point, not knowing what the problem is. I've attached the JD parts catalog page and the 8A tech manual page for anybody's reference. How does this thing come off? Thanks for any help that might be offered in getting this piston off. gthawus

 

[Tx Jim]

It appears the only thing that could be restricting the piston(parts key #8) on the shaft are the seal/BU rings(parts keys #6 & 7). Did you find any blemished places on the packings that are visible?? Rather than destroy something I think I would replace the visible packings and reassemble the cylinder. The area for a leak if parts keys #6 & 7 were faulty would be very small.

 

[gthawus]

Hi Tx Jim. Parts key #6 & #7 were removed easily from the piston #8 and the packings on the piston look OK. The wear ring looks a little worn. What brought all this about was pretty bad leakage out the cap end of the cylinder as well as slippage of the dipperstick. I'm thinking this slippage was due more to leakage a the piston end because its rate of fall seemed to be faster than the amount of fluid I was seeing coming out at the cap end. There was a lot of black muck in the leaked fluid so probably the packing (#14) in the cap end is bad. This packing is inserted inside the seal #12 (called the gland #N in the Tech manual diagram). This seal/gland must slide off the rod to get new packings in it and the problem removing the piston on the other end is stopping that. The piston must come off somehow or else the seal/gland could never have been put on at the time of manufacture. So how to remove the piston is the big question. Thanks for you interest. gthawus

 

[Tx Jim]

I suppose I can't see the "forest for the trees" because you encircled parts key #8(piston) along with parts keys #6(G BU rings) & 7(F oring) as the trouble spot.

 

[jd110]

I agree there is nothing left holding the piston on. I would try holding the pin end of the rod in a vise. The grab the "guide" and slide it forcefully toward the piston like a slide hammer action. The impacting action of the guide slapping against the piston should knock it off without damaging it. I have used this method many times on all types of cylinders, including 8A cylinders.

 

[gthawus]

Hi JD110. Remember, you helped me before with the adjustment of my dual stage clutch. That was last summer and the disk thickness was down to the minimum but its holding up fine. My attention is now on these hyraulic cylinders. There's not much doubt in my mind that the piston has to slide off the rod end but it looks like it'll take a press to do it. I tried with a little more pressure on the puller and zero. The 'guide' spins and slides up and down the rod but not freely enough to slap it against the piston. The packings are still inside it and can't be easily taken out until the guide is off and they grip the rod to much for any quick movement of it. Thanks, gthawus