My gear shift lever had a tendency to rattle in second gear during acceleration. The rattle sound was caused by the ball on the end of the shift lever vibrating in the lower slot of the shifter box. This was caused by wear on the ball end and steel plates.
To repair, first remove gear shift lever knob, the shift gate and shift boot. These instructions are for a 1971 and early 72 car.
Then remove the four bolts that hold the shifter box to the console. Note that the shift detent has be removed from my shifter box to improve the shifting.
Then remove the ash tray to gain access to the shift linkage U joint. Caution, the cigarette lighter has power with the key off and there is a hot wire near the shift linkage. Mark the U joint spline before removing. After the U joint is slid off the shaft the box can be removed from the console.
View of the lower shifter box and the ball end of the shift lever.
Remove the shift lever by removing the retaining clip and the pin at the middle of the lever (note the right/left side position of the lever). The slot has steel plates on both sides that guides the ball on the lever. Remove both plates (keeping track of their front and back location) and clean them and the slot area. They just slide out of the box.
Insert a shim washer on one side behind the plate and check free play. Note that the washer had be trimmed on one side to clear the casting on the box. The washer I used was about .005 thick and was purchased from Ace Hardware. The shift lever can also be shimmed at the center pivot to reduce side play.
Lube the assembly well with light grease and reassemble.