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| Situation | When we made our offer on the rod, to the best of our memory, we don't recall noticing any
fluid leaks on the car, yet when I had the car safetied, we discovered the left rear shock has a leak. We suspect that Charles had driven the car over fron Montreal that night a little too much exuberance and hit one of the many deadly bumps on Highway 417 a little too hard and ruptured the seal. Sinec there is no way of proving this, we just chalked it up to leason's learned. Since the spring is what holds the car up, not the shock, we determined the car was still drivable though one had to watch out for those bumps. Since it was already September, the car would only be on the road for a couple of months before the snow flew. |
| Analysis | A quick phone call to Aldan provided some insight to what our potential problem was. Aldan shocks could rupture for either of two reasons: 1. Shock was installed incorrectly. That is, the two mounting points are not directly in line with eahc other, or 2. The shock had 'bottomed out'. Aldan coil over shocks do not include an internal 'stop'. A subsequent visit to a Tire Shop confirmed our suspicions that there were no snubbers (rubber bumpers) installed on the chassis above the axle. We also noted that the shocks were installed correctly. So in summary, it appears the shock ruptured from bottoming on a bad bump. Fortunately, Aldan shocks were repairable, just a matter of sending the units down to California!
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| Shock Removal | With the arrival of snow, we put the car up on jack stands and pulled off the tires. We chose to take both coil over shocks off and have them rebuilt to ensure both sides were equal. Right Side
Thus the weight of the car was taken off the rear axle and it was left to hang under it's own weight. Now the rear springs were no longer under compression and it was a simple matter to remove them.
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The Repair Part 1 |
After carefull removal and packaging, the shocks were sent down to Aldan Shock Absorbers in
California. Within a week the shocks had arrived and were repaired. Come the first week in January they
were back on the car. Fantastic turn around time and Aldan were excellent people to deal with. Upon examination of the units, Aldan concluded they had bottomed out (both, not just the driver's side) just like we suspected and not only were the seals damaged, but the main shaft was also bent. Aldan made the necessary repairs and recharged the units for a price well below what was originaly quoted. Putting the shocks back on the car was straight forward procedure - a reverse of what was required to remove them. It transpires the shock spring was a "blue" banded unit from Aldan meaning it is spec'd in at 250 lbs/in compression. For a sedan Aldan recommends a 300 unit but I couldn't afford to make the change so they suggested I pre load the spring by about 1 in by running the locking rings up by that much which we did. I also set the dampening to 2 stops short of the stiffest setting to minimise the likelihood of bottoming out.
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The Repair Part 2 |
My next challenge was determining how to mount a flat bottomed rubber block onto a curved frame.
We have a local welding shop that is well versed in Hot Rodders and comes highly recommended. So I took my
drawings and photos down to Johnson's Welding to discuss my dilema. Bob Johnson was very helpful and open regarding
my situation - which wasn't quite as simple as we had thought! (it never is, is it?).
It transpires the rear end suspension on this Chev is what they call a trangulated 4 bar linkage. In this case, there are two bars attached to the outer ends of the axle houseing that run forward and attach to the car frame. Another two bars are attached to the top of the differantial housing and head diagonaly forward to the inside of the car frame. (I'll supply a diagram soon). The upper linkage arms are about half the length as the lower ones when you measure from their pivot points. When you encounter a bump, the geometry of the configuation comes into play. As the rear end rises (in relation to the chasis) it will rotate since the upper and lower control arms are of different lengths. Since the coil over shocks are bolted directly to the chaisis and rear axle, they experience a stress as the axle housing tries to twist. The net result is something has to give, often the seals in the shocks rupture and the shock shaft may bend. Interesting, this theory supports what had to be repaired on the units. Also, I had noticed the bushing sleeve on a couple of the shock mounts had also been distorted which is consistent with the transfer of stress. Aldan makes a spherical bearing housing that can be inserted in the mounting hole thus allowing the mounting bolt to rotate in the shock. I have just taken delivery of a set and will install them after I resolve my next challenge! Actaully, I should have forseen this issue. In order for the spherical bearing to fit inside the existing shock mounting hole, it will have to use a smaller diameter bolt. In this case a 1/2" size. So now, I need to address the axle mounting method as it is currently sized to handle the existing 5/8" bolt. So this is where I am at today (April, 2001).
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