VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Lever Shock test

I have removed my single action lever shocks from my 1940 Chevy PU.
I have found that there is no filler plug in the cap so I filled them through the relief valve plug.
When the lever arm is fairly easy to press down and it springs back up just fine by itself.

How much force should be required to depress the lever arm?

Is it correct to assume that if it is too easy, the relief valve is too week or seated properly?

How can I test the relief valve?
Are their replacement parts?

Thanks,

Mike

A shock will provide resistance in proportion to the speed it is moved. If it is working correctly, the harder you push the more resistance there will be.

Down will be fairlyhard. Parts are next to impossible to find. Shock may not be completely full.

Hi Mike,

I am surprised that there is no fill plug in the sheet metal cap. I do not have access to a 1940 shop manual so that might be correct for that year. The fill plug is a screw with a slotted head near the top of the stamped steel cover..

A single acting shock only has resistance when you pull the arm down. It takes some extra care to get sufficient fluid into the shock. Many of us use hydraulic jack oil because it does not foam and seems to have the right viscosity.

You need to slowly manually cycle the shock through 4 or 5 cycles to get fluid into all the working chambers. You will probably have to add oil a couple of more times. You want to oil level up to the fill plug when you finish.

My observation is that most of the time the shock has leaked all the fluid out past the shaft seal. The internal parts are pretty durable. Adding fluid properly makes them work fine. Until it all leaks out again.

Well I bit the bullet and opened up the shock in question...
The parts looked pretty good other than the valve that sits on the cam end of the spring, inside the piston. It was smashed. It looked like it might have been inserted backwards and the piston crushed it....
so now I’m looking for that part... in the parts book it’s labeled as 7.346
Anybody have any throwaways that I can salvage a valve out of?

Also, does anybody know the correct position of the relief valve?

Thanks,

Mike

Mike, you may have the same type of shock that I have on my truck, according to Apple Hydrulics, the correct way to add fluid is to take off the end cap.

Well, all 4 shocks are like that so I guess you are right.
Are the gaskets available?
You wouldn’t happen to have an old shock available for parts?

Palm Harbor? I’m down in St Pete... small world.

Thanks,

Mike

Mike, if you call Apple Hydrulics and tell them that you are sending $10 for pizza at lunch for them and then mention that you need gaskets, they will send you an envelope full. Sorry no parts but you can sometimes find cores on Ebay for cheap. BTW, you and I belong to the Gulf Coast Region and you send me tech articles for the newsletter.

At some point I knew that was going to happen.....????????????

Thanks...

For something like the shock covers I would cut new gaskets myself, thin cork or paper gasket sheet isnt expensive and can be used where ever oil jointing is required.
Tony

In the process of rebuilding, I completed the two back shocks. Mostly just cleaning and installing gaskets as suggested above. I finished the one good front one the same as the back ones but found that when I tighten the relief spring plug they become so hard when depressed that they almost lockup. I can adjust the relief plug to get good resistance. I thought it might be the shock itself so I proceeded to rebuild the other front shock using the valve from one of the other shocks that worked and got the same results.

Any comments???

Is this supposed to be some kind of a adjustment?

Thanks,

Mike

Hi Mike,

There needs to be more resistance to movement than you might think for a single acting shock to have an effect. I am not aware of any adjustment.

The key question is whether or not the lever will move at all when you apply force to it. On my '37 they move slowly no matter how hard I push.

The forces from the action of the suspension are much greater than you can ever apply by hand. You cannot manually apply enough force quickly enough to make the relief valve open. The only oil flow you can create by hand is oil flow through the orifice. You are feeling oil leaking around the relief valve threads when you "adjust" it.

Remember that the resistance is on the rebound action, not the compression. The shock is controlling how quickly the axle "drops" back to normal ride height.

One suggestion is to determine if you can manually make the relief valve open by pushing/striking on it with a punch or some other method. This will confirm that the relief valve is not stuck.

After you re-install the shocks keep a close eye on the area where the shaft comes out of the housing. Most of these lever action shocks leak there due to the seals hardening and wear on the shaft. Rebuilding is expensive because there is a lot of work to spray weld that area to build it up and then machine it back to good finish for sealing. I had mine apart completely and installed a lip type seal. It did not work due to the pitting and wear on the shaft.

I checked all the valves and they all seem to work. Your comment got me thinking about dried seal.
I’m going to try to move the arm by extending its length with an add on.... maybe if I can get it moving with the valves installed, it might loosen it up.... we shall see...
In the meantime, thanks for the comments.

Mike

Hi Mike,

I know this might be a crazy question. When you had the shock open and empty of oil how smoothly did the lever move? That would be an indication of the fit between the piston and bore.

When I had my shocks apart I used a brake cylinder hone to lightly clean the bore. I also tried to clean-up the shaft in the seal area but there was too much pitting to get a good sealing surface.

That’s the strange thing, everything works smoothly until assembled. As I tighten the relief valve down, it’s gets harder to move the lever until it won’t move at all. My present plan is to build an extension to the shock lever and see if it moves then. If so, then compare it to the rear shocks which have longer lever arms. I never had the shafts out (don’t know how to do that or have any replacement seals) Trying to find a replacement internal valve has been hard enough.

We shall see...

Thanks