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Chicagoland MG Club: Driveline
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  Chicagoland MG Club:Driveline

Just a Simple Wrench
by Ann & Jake Snyder
Well Sprung

Ann and Jake Snyder A fellow club member first hinted that we had a problem with our rubber-bumpered (raised ride height ‘741/2) GT. “It looks”, he said, “that your GT is going down the street kind of sideways”. As this message was given far into November, and we had missed the October storage date by a shameful margin (but there had been no snow, and, therefore, no salt yet), we felt that we did not have the time to find out what was wrong. We had no doubt that something was seriously out of specification when we took the car to its winter storage the next Sunday. With one of us driving the GT in question, the other of us noted that the right rear seemed to stick out at least six inches to the side. Needless to say, we drove the car with great caution after retrieving it the next spring, and parked it until we could determine the origin of the tracking problem.

We quickly checked for rusted out rear spring attachments, but everything was still solid. That left the springs themselves, as there is nothing else that can break without leaving large pieces in the rear view mirrors.Cat checking out the rear axle assembly We had a lot of little problems associated with the rear axle, so we opted to take every thing apart and reshim the differential, replace the pinion seal, replace the breather, replace the emergency brake cable, fit fresh brake lines and fix the tracking problem. Many of these are easily accomplished with the axle on jack stands of a convenient height, rather than fretting under a car with very limited light, line of sight and clearance when (not ” if”) big wrenches, the oxy-acetylene torch and hammers are needed.

Broken leaf springAfter removing the back half of the exhaust system, we loosened the propeller shaft and undid the flexible brake line, closing it off with a pair of locking pliers cushioned with blocks of wood. The rear attachment shackles came out rather easily because of the rubber bushings, but one of the front bolts had to be sawed off. The rear shock absorbers were removed from the body with the intent of re-using the links. We had left the road wheels on and simple pushed the axle from under the car. The rebound straps were cut because we planned to use new rebound straps, and the thirty-year old nuts on the rebound strap attachment studs were heated red hot to eliminate breaking the attachment studs. Removing the axle from the car was better by far than removing the fuel tank before the torch work started.

We found the source of the tracking problem as soon as the left spring was unbolted from the axle. The top leaf was broken, and the two ends let the axle move a little from side to side and front to back, giving, in effect, a rear set of wheels that steered without any instruction from the driver behind the steering wheel.

Heating rebound strap nuts with torch
Removing the rebound strap attachment nut

The replacement set of springs was an old set from another GT that we had taken to a commercial truck spring shop with the name Commercial Truck Springs. We have had several sets of springs redone the same way, all for chrome-bumpered cars: We ask for an extra full leaf on top, and that any broken leaves be replaced in pairs. As the resulting springs have eight leaves rather than the GT standard of seven, we get a set of shackle bolts made that are an inch longer than the originals. This makes re-assembly very simple, and the excess is simply cut off. The rebuild cost is competitive with the price of new springs of “guaranteed” steel and the cost of shipping.

Everything went very well until we got to the part of refitting the rebound straps and shock links. Even with a sack of concrete mix, two car batteries and the smaller one of us in the back of the car, there was no real travel left in the rear suspension. We checked with club resources, and were more than dismayed to learn that limited suspension travel could result in catastrophic oversteer. So we parked the car again until we could figure out some way out of the limited suspension travel. One suggestion was to remove the springs, take them to Commercial Truck Springs, and get them de-arched. Good, but we held this as the last resort, though it will be done with the next set of springs. Then, discussing the matter over a glass of cabernet, we realized we had reached into our box of suspension parts when we got the new rebound straps. And the only parts we had ever put into that box were for chrome-bumpered (low ride height) MGBs.shock absorber links and rebound straps We ordered the correct parts, both shock links and rebound rubbers, and checked them against what we had so much trouble fitting. Yes, indeed! The chrome-bumpered parts were too short. Had someone put another rear axle, a complete transplant, earlier? Could that have accounted for the mysterious “71” in junkyard-yellow paint on the bottom of the differential housing? Very likely. The measurements of the hole-to-hole or stud-to-stud lengths are provided for future reference, and are for chrome and rubber bumpered MGBs.

                   Chrome            Rubber
Rebound Strap    8 1/2 inches      9 5/16 inches
Shock Link       8 1/2 inches      10 1/4 inches

The car now tracks perfectly, and does not seem too stiff. It has a useful load capacity, a concern for us because we have to use the GTs for everything or rent another vehicle. We noted that five eighty-pound bags of concrete mix lowered the car by 1 5/8 inches. Allowing an eighth inch for tire compression, that gives a spring rate of about 133 pounds per inch (400 pounds divided by 1.5 inches divided by two springs). We also noted that carrying four hundred pounds of concrete requires the utmost attention to driving, as any sudden deceleration will result in an unacceptably high wear rate to the back of the seats, the steering wheel, and the dashboard, as well as to the operator and passenger who are between said surfaces.

But the GT is now very well sprung.

©2002 Chicagoland MG Club, All rights reserved.