The crush spacer goes on the pinion shaft just behind the outer pinion bearing. It's possible that someone who didn't know what they were doing left it out when they installed the 3.73 gears. If that's the case then you are screwed. My advice would be to get a pinion bearing kit and set up the pinion again the correct way. You don't want to try setting the pinion bearing preload with used bearings that have been run loose.
If the crush spacer is there and you just didn't see it then you can fix the problem easily. Just clean everything and put in the new seal with a thin film of RTV sealant around the outer edge and grease the rubber lip. Then smear some RTV into the splines of the yoke and put it back on. Then use a new pinion nut with red locktite and torque the nut to 125 to 150 foot pounds and it should be fine. If the bearing preload was set correctly the first time with the crush spacer installed then this will get you very close to the same setting.
If the crush spacer is there and you just didn't see it then you can fix the problem easily. Just clean everything and put in the new seal with a thin film of RTV sealant around the outer edge and grease the rubber lip. Then smear some RTV into the splines of the yoke and put it back on. Then use a new pinion nut with red locktite and torque the nut to 125 to 150 foot pounds and it should be fine. If the bearing preload was set correctly the first time with the crush spacer installed then this will get you very close to the same setting.
