Technical Article

TD-TF Armstrong Shock Maintenance

(as appeared in the July, 2004 TSR)

By John Wright

While all of our T’s have hydraulic dampers, I believe it to be one area that does not get much in the way of maintenance or service. We all know the symptoms of a bad one; here are some tips to improve yours! Since a worn out shock is not serviceable by the average home mechanic, preventative maintenance is useful in extending the life further of these components. Bouncing on each fender will quickly tell youif a shock is bad or needs service. If it is leaking and you have filled it before, most likely it is shot and needs rebuilding by a qualified rebuilder of these units. A way to check a non-leaking shock is to separate the shock arm from the top trunnions and move it through its full travel or better yet, remove the shock completely. Do this safely and refer to your shop manual for the procedure to release the shock arm or to remove it from the chassis. Assuming you have removed the shock, secure it in a vise and move the arm through it’s full up and down travel. You may notice weak spots or inconsistencies in the resistance as you move the arm.


The main thing we are trying to do here is to clean out the chambers and remove old hydraulic oil and filings and deposits. Remove the top filler plug and the valve assembly under the arm. Gently remove the cover plate if fitted. Drain out all the old fluid while exercising the arms through the full stroke. Inspect the inside of the shock body as well as you can to see if there is any obvious damage or wear. Once drained, refit all the covers and plugs and fill the chamber 12 with kerosene. Next work the arms to move the kerosene around to flush. Remove the valve and top filler plug and drain out the kerosene and then repeat the process 3 or 4 times until you are satisfied that you are not getting any further debris. Drain all the kerosene to make sure that there is none remaining. Inspect the valve assembly for cleanliness but do not disassemble it. Adjustments to the valve are outside the scope of this article. Make sure the valve assembly is reinstalled as it was originally. Reinstall the remaining parts and fill the body with the recommended shock oil or SAE 30w non-detergent oil. Fill the chamber and work the arms several times to expel any air. Refit the shock and check the level once more. It should be about 5/8” from the top. That’s it. This can be done to any Armstrong shock. Be aware that like most old things, disturbing the “dirt” may cause a problem in a working, but very marginal part. You may end up having them rebuilt anyway. Such is the life of a 50 year old part!

Information for this article came from Internet searches and personal experience.

New Fangled Timing Lights

Some of you no doubt have seen and used the relatively new inductive dial-type ignition timing lights. I have a Sears unit, which I have found to be quite useful, especially with engines that do not have any type of timing marks on their crankshaft pulley other than a notch at TDC.

To use this type of light, hook up as you would normally. Let’s say you want 10°. BTDC. Turn the knob to 10, run your engine at the specified idle speed for timing checks. With the light aimed at the mark, adjust your distributor until the mark in the front cover lines up with the notch in the pulley. Snug up the distributor clamp. Simple as that! You can do the reverse too if you want. Let’s say that you are pleased with the way your car is running. Using this light set it to 0 then rotate the knob while you are idling the engine. See what reading you get, that is where the timing is now set. Note that setting, along with your idle speed and you should be able to replicate that setting again if you have the need to remove the distributor. This can be useful in determining maximum advance and a worn distributor shaft. With a worn distributor shaft, and any timing light, the mark on the pulley will be seen to jump around a bit, indicating changes in dwell, affecting ignition timing.