| I hate it when I have to disassemble something that I had already installed back on the car, thinking it was in good condition. Since last fall, the passenger side front lever shock had leaked all its fluids out. This was the replacement that I found used at a parts warehouse. I thought it was time to fix it before installing the inner wheelwells. In the US there are shops that rebuild these shocks, but being heavy items, it didn't seem feasible shipping them overseas. I decided to give it a try and experiment with a leftover shock that was badly seized. The shop manual is rather vague when it comes to rebuilding front shocks. I discovered that the splined shaft is smaller at the other end, so I thought it's as easy as putting it in a hydraulic press and press the shaft out. I was wrong. The press gauge pegged at 20 tons, but nothing happened at my shock. Then I recalled once talking to a man with a '38 Buick, Jari Vuorinen, who had fixed several knee action shocks for his own cars. Luckily I had retained his phone number, and he kindly revealed the secrets of shock rebuilding, over the phone. |
| Update 27 April 2005. Bela Kiss
from Switzerland http://www.buickbombsight.org/road.html,
asked me for some additional advice on how to disassemble the shocks to
replace the seals, and he asked me to put that additional info here as
well. He also gave me a few tips. As I pointed out, and Bela can
confirm, this is not for sissies! 1. MEASURE AND MARK. Punch or scribe the end of the shaft (both ends) and arms to mark their relative position. Measure the diameter of shaft ends. There's usually just enough shaft protruding so you can have a measure. One end is slightly larger than the other. Also, measure the sweep or travel of the arm before taking it all apart, so when re-assembling, you can trial-fit and verify the correct position of the shaft, relative to the cam inside. Before splitting the A-arm (with an angle grinder), you should measure the distance between the eyes (where the upper pivot pin comes), so when pressing the arms back on the shaft, you are able to get them to the original depth. Remove the end caps and drain all oil out. If you are going to just replace the seals, and the shock is working well otherwise, you don't have to disassemble the valves or pistons. You are just going to pull the arms off the shaft. If the shaft is in good condition, AND you can find correct size seals, you don't have to press the shaft out. In many cases you will have to. 2. FABRICATE A MANDREL. Even though you have marked the relation of the arms to the shaft, you have to fabricate a mandrel, that clamps to the other arm half, and fits snug through the eye on the other half, simulating the pivot pin, forcing the eyes to line up when you press the arm halves back on the shaft. 3. PULL THE ARMS OFF THE SHAFT. To replace the seals, you must split the A-arm in half (the arm halves are welded together where they seem to cross), and pull off the halves from the shaft. You might think that the shaft can be pressed through, but it can't. The shaft is NOT splined all the way through. It is splined to both arms (different size splines) and to the cam inside (third size spline). In step 1, you measured the shaft diameter at each end. You have to pull off the arm on the larger end first. This may be tricky. There's not much space under the arm eye for a puller. I ground some material off the arm eye with an angle grinder, to make room for the puller claws to grab on. I then turned the puller as tight as I could (nothing happens at this point), and then heated the eye with an oxy-acetylene torch. Ask a friend to work the puller while you handle the torch. It will come off eventually. When the arm is apart, I simply welded back the amount of material that I removed, and dressed the weld bead back with a belt sander. Now you have the arm off the large end of the shaft. Pry out the old seal. Again, you need to apply some moderate violence. Once you have the seal off, look at the sealing surface on the shaft. Does it look pitted and corroded? If it is relatively smooth, you are lucky. You can just remove all dirt and deposit with a piece of sandpaper or emery cloth, and replace the seal. Then pull off the other arm and do the same. Now you should be ready to put it all back together. If the shaft is pitted, you have two options. Either you remove the shaft so you can weld some material on the shaft to fill the pits, and true the surface on a lathe. Or follow Bela's tip and you might be able to get away without removing the shaft, by bonding a thin metal sleeve on the shaft, like the ones that are available for harmonic balancers to restore the front seal surface. You might be able to find a suitable bronze bushing, for instance. In this case, pull off the other arm also and do your trick. Otherwise, move into step 4. 4. REMOVE THE SHAFT. Suppose you decided to press the shaft out. In this case, there are two options. Either you pull off the arm on the smaller end, too, or you press the shaft through the eye on that arm. The latter way is less work, but needs more force. If I remember right, it required some 5-10 tons to come off. Now you have the arms and shaft loose. If you pull off the arm first, you still need to press the shaft off the splines on the cam inside. Now you have both arms and the shaft apart. I had to remove the shaft anyway because I had to open up the bore size on the shock body, because I couldn't find a seal with the correct outer diameter. See the original text with the pictures below. Bela was able to find the correct sizes for his, as follows: "The sizes we are going to use are 19.05 x 33.33 x 6.35 and 22.22 x 34.93 x 6.35. Not easy to find, but available" Thanks for the tip! Obviously, these are imperial measures converted to metric. The latter translates to 7/8" x 1-3/8" x 1/4" in inches. If you are from the US, you figure out the other one yourself - I'm not very good with the fractions. I prefer millimeters. Once you have trued the shaft surfaces and replaced seals, you are ready to put everything back together. Or you can go to step 5 to disassemble and clean the whole thing. 4. REMOVE THE CAM. On the underside of the shock body, there's a core plug. It looks like a freeze plug. Tack weld a nut on it, and use a slide hammer to pull it off. Now you can see the cam that actuates the pistons. It is tensioned between the pistons, but it will slide out if you pull it. 5. REMOVE THE PISTON ASSEMBLY. You don't have to, but the piston/valve assemby can now be pushed through as an assembly, to facilitate cleaning. Pistons are held together with two VERY long and tiny screws. You can see them when trying to pull the pistons apart. Screw heads are hidden under small plugs. But there is no real reason to disassemble the piston assembly, unless you accidentally broke the screws. ASSEMBLY is the reversal of disassembly, hahaa. If you removed the shaft, you must install the End Caps that limit piston travel, and trial-fit and find the correct position of the shaft relative to the cam. Verify the position that gives you the same arm travel that it originally had. Once you find it, the shaft can be slid through the cam with a soft mallet or press. Then you can install either one of the arm halves first. You need to press it on the shaft, but be careful - you don't have room for the puller if you went too far! Now you are going to press on the other half, with a mandrel guiding. Measure the distance between the eyes (where the upper pivot pin comes), as you press, and stop when the distance is equal to what you measured in step 1. Congratulations! |
 Rebuilding
things like lever shocks is actually one of those things I would like
to
see on the Internet. I was able to find absolutely nothing. So I
decided
to share with you what I did. Jari told me that the shaft is not
splined
all the way through, but at the ends only. So you must cut the legs of
the A-arm apart where they cross each other. Then you have to use a
heavy
duty puller to pull each leg off the shaft. You probably have to help
the
puller by heating the eyes HOT with a torch like I did. You are going
to
replace all seals anyway, so it doesn't matter if they burn.
Unfortunately
I had already pressed the shaft back in place when somone suggested I
should
take some pics!
Below: On the bottom side, as well as on the top side, there's a press-fit mild steel cap. Weld a little nut on the cap, and pull off with a slide hammer. When tapping them back, I used a dab of sealant on the perimeter. Inside, there's a cam, much like the shape of number 8, that is pressed on shaft. It moves the pistons back and forth. You can see the cam in the pictures below. Once you have pressed the shaft out, you can withdraw the cam through this opening on the bottom side. You can then tap the pistons out as an assembly. The pistons are bolted together. Pay attention to the valve numbering on each piston, for instance 3D and 3F. They usually come with different valving. Mine was valved stiffer for jounce than for rebound. |
  |
 The
shaft was badly corroded under the seals. I welded a lot of new metal
there
with a MIG (MIG is better than TIG because the weld is harder = wears
off
slower), and trued the surface in a lathe. Obviously, you are going to
install modern lip seals, right? You'll need two sizes of seals. Not
only
the shaft has different diameter at each end, but the recess in the
housing
has different diameter, too. At the bigger end, I was able find a seal
that fit without modifications. It's not a metric seal, but in the
catalog
it was listed as 22.22 x 34.92 x 6,35 mm. In inches it's obviously 7/8"
x 1-3/8" x 1/4". However I wasn't able to find a suitable seal for the
smaller end. I chose a metric seal measuring 20 x 35 x 7, and had to
open
up the housing to 35 mm diameter with an arbor. |
 As
I stated earlier, the
pistons have different valving for jounce and
rebound. The valves are missing from this picture. The pistons are
screwed
together, and the screw head is hidden behind a press-fit plug. I
drilled
the plugs off to gain access to the screws. I'm not sure if the plug is
there to prevent the screw from coming loose, or to prevent oil from
bypassing
the valve. Anyway, I replaced the plugs by cutting small discs out or
aluminum
rod, and tapping them into place once everyting was assembled and
looking
good. Under the bolt head there's a spring, that allows you to take up
any slack between the cam and piston, yet allows the pistons to move
freely
without binding. If you look closely you'll see that the screws have
allen
heads. I snapped the originals while whacking the rusted and jammed
pistons
out.
There was yet
one defeat
left. When replacing the screw-on end caps, I decided to try
polyurethane
sealant instead of paper gaskets - LEAKS! |