Rebuilding a Giant-Vac Log Splitter Ram

Specifications:

Manufacturer: Giant-Vac (Now SCAG)
Model: 2425 "The Big Giant"
Cylinder: Giant-Vac P/N 61017 24" X 4"
Engine: 5 hp Briggs and Stratton


I was hunting for a log splitter and did not have any budget to speak of. I started talking to my neighbor and mentioned my search. He said that he had an old log splitter that had been sitting at a relatives house for years and years.

A few minutes later we were off to get the old log splitter. A quick checkup to make sure the engine had fresh gas and oil... a shot of starting fluid and the old Briggs and Stratton fired right up.

Immediately a twenty foot plume of hydraulic fluid was streaming out the main cylinder and my search for a cylinder re-built kit began.

I looked high and low, called stores that had bought Giant-Vac parts when they went out of business, eBay, YouTube, Amazon, forum boards... nothing.

I thought about just buying a replacement cylinder, but the idea that I would toss all that steel just because I couldn't find some seals... really? No, I decided to tear it down and was determined to fix the original unit.

What follows here is a record of what I did to rebuilt that hydraulic cylinder. There may be an off chance that someone else out there has this same cylinder leaking; I hope this information can help. It has been a couple years since I did this and I have split many cords of hardwood. I have not had any leaking or other issues whatsoever.

Top view of the splitter

Overview of the splitter (after it is fixed)

Disassembly: Removing packing nut, piston, and ram from cylinder bore

Once the cylinder is removed and as much of the fluid is out as possible clean it up and put it in a vice or secure it by some other means.

The packing nut on the end has a large hex feature cast in that should rotate freely 360 degrees.  There is a groove cut into the cylinder near the packing nut (See photo). Make sure to take a tooth brush and clean this out very well.

Access groove for retaining ring

 

Use a flashlight so you can see what you are doing and slowly rotate the packing nut until you see the end of the retaining ring. The packing nut is held in place by this retaining ring.

To remove the retaining ring you need to find the square end of it then take a very small flat head screw drive and slip it under the end. Once the screw driver is under the end you apply very light leverage while rotating the packing nut towards the screwdriver. This takes the end of the retaining ring and feeds it up and out of the groove.

Small screw driver used to remove the retaining ring

 

Another view of the retaining ring being removed

 

Retaining ring removed

 

Once the retaining ring is removed the packing nut, ram, and piston can be removed from the cylinder bore.

 

Packing nut, ram, and piston removed

 

 The piston on the far left of the photo above is held onto the ram with a large nut. There is an O-ring underneath the head of the piston and a Teflon (assumed) ring that seals against the bore.

 

 

Disassembly: Removing the piston from the ram

 

The nut is peened in place as shown in the photo below. I recommend taking a Dremel tool with a small grinder and removing the plastically deformed material so the nut can come off without binding.

 

I attempted to use a power drill since I didn't have a Dremel at the time. I must not have done it well enough because when I took the nut off all the threads in the nut were stripped and ruined. Fortunately the threads on the ram were only slightly damaged near the end.

 

Peened nut on ram

 

Mark the direction of the piston and remove it from the end of the ram.

 

Piston marked, then removed from the ram

 

Disassembly: Removing the packing nut from the ram

 

Slide the packing nut off the piston end of the ram.

 

As can be seen in the photo below there was not much left of whatever seals and/or packing originally came in the cylinder.

 

Remnants of the OEM seal

Disassembly of the cylinder is now complete.

 

 



Cleaning:

Remove the old seals and O-ring from the packing nut and thoroughly clean it.

Outside of packing nut

Inside of packing nut

Packing nut over view

Wipe down the cylinder bore to remove the remaining old and contaminated oil.

Remove the small O-ring on the cylinder ram that seals against the piston.

Since I could not find and replacement part for the wear ring on the piston I left it alone. The splitter has worked well even with the extremely rough appearance of the piston.


Parts needed for re-assembly:

As mentioned at the beginning of this post there was no source of information regarding what seals were originally in the unit and definitely no "rebuild kit" for sale.

I measured the O-ring and wiper grooves, the bore and rod diameter. I then selected off the shelf parts that I believed would work. I used Parker's free design guides heavily (see reference section at the bottom of this post).

I listed the McMaster-Carr part number and price for the items. This should give you enough information to determine what the item is, and a rough idea of the cost should you choose to source them else where.

You'll need one of each item below unless you re-use any, see notes column.

Part	Vendor	Part number	Cost (each)	Cost (min buy)	Notes
Urethane Rod Wiper (AN 959 / 940)	Zoro	G1614873	$1.21	$6.05	The wiper that removes any deris from the rod when retracting into the cylinder. This makes sure all your seals inside don't get destroyed. You really should replace this!
O-ring Lip Seal (2" ID) x (2.5" OD) x (.375" Ht) x (.25" Width)	McMaster-Carr	9514K246	$6.86	$6.86	This is the packing nut to rod seal. I'm not sure what was in this gland originally, but this works well.
Split PTFE Back up ring, Dash no 329	McMaster-Carr	9560K85	$1.24	$12.38	Backup ring to go behind the O-ring lip seal
Split PTFE Back up ring, Dash no 240	McMaster-Carr	9560K551	$2.31	$11.55	Backup ring that goes between the packing nut and cylinder bore. I ended up not purchasing this part and reusing the existing OEM one.
Buna-N O-ring Dash no. 240	McMaster-Carr (or local hardware store)	9452K191	$0.22	$11.15	O-ring that goes on the outside of the packing nut and seals against the cylinder bore. My local ACE harware has a decent O-ring selection in the plumbing department and I was able to purchase one locally for $1 or so. I deemed this better than buying 50.
Buna-N O-ring Dash no. 029	McMaster-Carr (or local hardware store)	9452K116	$0.07	$7.07	O-ring that goes on the rod and seals against the inside of the piston. I also purchased this O-ring at ACE hardware for a few cents.
Hex Nut, thin, 1 1/2" x 12	McMaster-Carr	93839A865	$9.11	$9.11	Hex nut to hold piston onto rod. ONLY needed if you damaged or lost your original.
Wedge Lock Washer 1 1/2"	McMaster-Carr	91074A160	$9.24	$9.24	Extreme vibration lock washer for the piston nut. I decided to use this instead of peening the nut in place.
Total Cost			$30.26	$73.41	Should give you a rough idea of cost

Reassembly:

The first thing I had to do was take a jeweler's file and clean up the rod threads that got messed up.

Next, apply a light coat of O-ring lubricant (Vaseline works fine) to the small -029 O-ring and put it in the rod groove that will be covered by the piston.

-029 O-ring shown in rod gland

Take the O-ring lip seal (P/N 9514K246) and lubricate it. Make sure it is facing the correct direction (see illustration below) and place it in the gland in the packing nut. This can be quite a fight, but it can be done without damaging the seal. I ended up taking a hair dryer and warming the seal until it was pretty hot but could still be handled with bare hands.





Illustration showing the packing nut components with proper orientation

O-ring lip seal in packing nut gland

Now take the split -329 backup ring (P/N 9560K85) and place it behind the O ring lip seal. For those of you wondering why this is here. It is not being used as a backup ring in the traditional sense. Rather, it is being used a spacer to help constrain the O-ring lip seal since I could not find a lip seal that would properly fit into the gland as it is machined.

Placing the backup ring in behind the lip seal

Packing nut with O-ring lip seal and backup ring installed

Next take the AN rod wiper P/N G1614873 and place it in the appropriate inner groove.

AN wiper installed in packing nut

Take the -240 O-ring (P/N 9452K191), lubricate it, and install it on the outside of the packing nut.



-240 O-ring installed on the packing nut

Install the split -240 backup ring (P/N 9560K551) next to the -240 O-ring making sure it is on the correct side.

Apply a light coat of hydraulic oil to the rod and slide the packing nut onto the rod starting at the threaded end of the rod. Take your time to make sure your don't damage any of the seals when you are feeding it over the edge.

-240 backup ring installed, and packing nut on rod

Place the piston in place using your mark on disassembly to ensure proper orientation (I'm not sure if orientation is 100% critical, but I kept it the same just for good measure)

As can be seen, the piston and ring on this unit is really rough, but it still works.

Close up of piston showing damage

Piston in place with Nord-Lock washer and nut loosely fitting

Once the piston is in place fit the Nord-Lock washer and hex nut. Torque them down as tight as you can get them. The torque listed on the washer was incredibly high. But we are using a low profile nut so there are not as many threads. I ended up using a 3/4" torque wrench and got about 600 ft-lb on there.

I put cardboard and foam on the ground to protect the ram and seals and make sure I would not be attempting to bend the rod as I torqued the nut on. I stuck a large steel bar through the hole where the splitter head connects to the ram and had someone stand on it while I torqued the nut on.

Nut torqued in place

Apply a light coat of hydraulic oil to the inside of the cylinder bore and feed the piston into the bore carefully. Once the piston and rod are in a decent bit, slide the packing nut down and carefully seat it into the cylinder bore.

Rotate the packing nut until the hole for the retaining ring is visible in the groove.

Hole for hook on retaining ring

Take the retaining ring hook and press it into the hole in the packing nut through the groove in the cylinder.

Hook on retaining ring inserted into hole in packing nut

Now rotate the hex feature of the packing nut away from the retaining ring to that it sucks the retaining ring into the cylinder

Rotating hex feature on packing nut to install retaining ring

Once all the ring is sucked into the groove orient the groove so that the start/end of the retaining ring is not at the opening. I did this just in case anything ever tried to vibrate loose.

That's it! Your ready to reinstall the cylinder and start splitting firewood!

I'm not covering filling or bleeding of the system since there are plenty of YouTube videos on the subject already.

One last piece of advice is to install a filter on the return line of the reservoir. It is not a lot of money, $20-40 of so and will greatly increase the chance of your seals lasting longer.

Here is a photo of the unit many cords after the rebuilt. This is about 1/4 of the total amount of Osage Orange wood that it split that weekend. If you've ever come across this wood, you know how tough it is. It's a little over twice the hardness of Oak!

Tearing through Osage Orange with no problem

References:


Parker Design Guides

The best way to make sure you get the latest version of the following excellent free design guides is to Google search the following and the .PDF will come up.

1) Parker O-ring Handbook ORD 5700

2) Parker Fluid Power Seal Design Guide  EPS 5370


Giant-Vac / SCAG Manuals

3) http://giant-vac.com/manuals.html


Good source for the bypass filter mention earlier and other hydraulic parts

4) http://www.baileyhydraulics.com/