John Deere 790 w/300 Loader - Hydraulic Cylinder rebuild kit confusion

[richmz]

The 300 loader bucket cylinders on my 790 had some leaking going on for a while. One got much worse. I researched rebuilding myself. I've done steering racks before so I opted to tackle this one myself.

My JD dealer about a hour drive away told me the AH176655 seal kit has been superseded to AHC17687. I went there the other day and bought 4 kits, 2 for now, 2 for spares when the boom cylinders act up.

I got the cylinder apart and removed the rod guide inner seal and outer seal. The AHC17687 kit does not have those 2 seals, but several others that don't match any of the seals on either the Bore or the Rod. Earlier today I discovered that the AHC17687 is only for the Bore, and AHC16981 is for the Rod. I ordered 4 of those kits today from HW. hopefully get them by Weds or Thurs.

However, can you help me identify what the "?*" seals are in the following diagram? JD Parts website is no help. Maybe they're for other cylinders.





These are plastic, split. Unsure where they fit.


Where would these go?





Thanks,
Rich

 

[richmz]

UPDATE:

I called my local dealer yesterday and the Service Manager said he'd review this with me. He offered for me to sit down with him and go over everything. I sent him my photos late yesterday with notes and specific questions. I may take the hour drive down there this morning to sit with him and pickup some other parts I need. Maybe then look at a new GM1060E mower as mine is now about 40 lbs lighter from 11 years of steel frame disintegration. I've rebuilt and bandaided it for the last few years and it's in pretty sad shape. I spoke with the Sales guy yesterday and he has one there in stock.

Back to the details.... I've learned a lot about how the parts system works at JD. It appears that the Bore Cyl rebuild kit(bought 4) covers other cylinder applications also. Now I see why the original seal kit got superseded. More money for JD. Of the 11 pieces in the kit, it looks like 4 or 5 are used for my 300 cylinders. 3 o-rings, the piston seal, and some form of replacement split square profile ring for the rubber NON-split square profile ring on the rod guide. Crazy thing about this part is I think it's just a side spacer for a very thin o-ring. Maybe even a fix for a design or machining error on thousands of guides. Another oddity is that this replacement split ring piece isn't as tall as the original so it has no sealing functionality at all.

So....what great parts value. $60.34 for the kit, mind you times 4, and 3 of 5 parts I likely could've gotten at ACE Hardware for about 3 bucks. If I knew then what I know now, I should've just ordered a handful of orange removal rings from HW, 4 piston seals, and reused those funky rubber NON-split square profile rings. Would've probably saved about $200. Hmmm, I may just return the 3 kits I haven't opened yet and do just that! And on TOP of all of this, there's a separate kit for the Rod with the 2 pieces I lost brain cells over at the beginning of this entire fiasco, trying to find which new pieces in front of me replaced them. Well, they were never there as I found out yesterday.

Or my other option is to spend another day or two researching what the heck the leftover seals are for and load 'em up on Ebay for some ridiculous price.

Apologies for being long winded about this but I probably have about 10 hours in this menagerie, and maybe 95% of that in research, making measurements, photos and analysis. I truly wouldn't have learned anything if I had somebody else rebuild these that's for sure.

I'll update this when I get it figured out and post as much detail as possible for future reference. Maybe it'll save somebody else the same grief I've been having.

Rich

 

[JimRB]

I rebuilt my curl cylinders on my JD440 loader. The kit came with only the parts I needed. It was about 4 times what it should cost compared to going to the local hydraulic shop and ordering seals. But it had everything I needed and nothing more.

Look in your gland nut for seals and wipers. Those are a challenge to get out and easy to get in with Kit King. Maybe easy enough to get in without the kit. Adam Booth Abom has some youtube tube videos where he builds new cylinders or repairs old cylinders and uses that kit to help install the seal. Kit King - Rod Seal Install Tool Set - 5 Piece Hydraulic U-Cup Twistor Installation Tool Set: Amazon.com: Industrial & Scientific

 

[richmz]

It has been a long time but I finally got back to this after being away a long time. I was successful in getting both cylinders rebuilt myself, reinstalled and they work fine. Here is a recap of my process. Hopefully it may help others, as well as a reminder for me when I get to do the lift cylinders in the not to distant future I suspect.

Taking the 2nd bucket cylinder apart was more difficult.

After removing the outer C-Clip, The gland could not be driven inward, even after soaking with penetrant. I had to use a large pipe wrench to get it to turn slightly. Then I had to file the outer gland where the wrench marred it so it could get past the cylinder opening.

Using a brass drift, alternating around the gland, I was able to finally drive it inside the cylinder. I cleaned the area and added more penetrant to help removal. Then I was able to install the removal sleeve. Note the thicker edge must be outward. I acquired some extras that had to be cut. Try to cut them so they are edge to edge tight in the inner circumference of the ring groove.

Now I tried to pull on the rod but the gland was now blocking the fluid port and it couldn't be pulled as air pressure was now built up inside.
I rigged up a makeshift air hose to the opposite port. After some hammering on the knuckle end with air applied, it fianlly came out.

After cleaning the gland and removing the old seals I was ready for new seals.

The inner gland seal has a specific profile. The open side faces the fluid pressure and the closed lip side faces outward.

I used my insertion tool to install it. Slick tool.

I also used the tool for the outer wipe seal.

I then added the remaining o-rings on the outer side of the glands. Both now complete.

For the pistons, installing the new seals was a bit tricky. I used a full circle smooth surface hose clamp to hold them compressed overnight to aid reinstallation later. I wrapped some tape around them to protect from the clamp.

 

[richmz]

The piston uses a large o-ring first then a special square profile seal. Old pieces shown lower left after cutting out.

I installed the Outer C-clip, gland, then piston to the shaft. I used Red Loctite on the piston attachment nut.

Before assembly I used a hone to clean up the cylinder inner wall where the gland rests. A good cleaning with solvent removed any residue from honing.

After adding some hydraulic oil to the piston, the gland and the inside of the cylinder wall, I then installed the rebuilt shaft assembly to the cylinder. Using the brass drift I drove the gland into the cylinder. It is important to drive it in very close to the end of the cylinder, just enough to get the outer C-clip locked in place. This will ensure the internal C-Ring clip is properly locked to the internal cylinder groove. My first try failed when I yanked on the shaft to test if it was locked it. I didn't have the gland in far enough the first time. 2nd time a charm and it got locked in fine. Same for the other cylinder.

Both done. I also had new hoses made. I added some JD Green to the bare gland ends to keep rust away.

Both are back on and functioning properly.

Rich