Posted: 4/28/2014 4:06:34 PM EDT
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I'm rebuilding a rear end (FIRST TIMER) for my brother's Mercenary Grand Marquis. It's from a cop car - 3.27 Limited Slip. I replaced all the bearing and races, got the backlash set at .009" (.008-.012" is spec) and reused the factory pinion shim. The trac lock clutches were recently replaced, so I got really lucky. I made a fixture to measure from the axle centerline to the pinion and it is .001" difference from the depth with the old bearing.
I apologize for the awful pictures as they're from my phone. The pattern on the drive side is perfectly centered both ways. The coast side is more towards the outside of the ring gear. The reference pictures I've found show the patterns on the ring gear in the same location on the drive/ coast. Is this acceptable? How could this be corrected? 
My OCD made my spend way too much time on this project already. Stripped down, wire wheeled, POR15ed, painted, new bearings and seals, and new parking brake shoes and hardware. 
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If it's original gears in the original housing on the original shims in the original location you simply have nothing to be concerned about.
In fact if found that if regearing if I use ford gears in a ford housing I've found that you may not need to make any shim changes at all. Visually your pattern looks fine |
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Pictures are not in focus and kinda hard to see with the sun on the monitor but as long as you got backlash back to where it was before you took the carrier out and you didn't effect pinion depth I would run it. I ALWAYS check backlash before I remove a carrier, it's a good habit to get in even with ones that are shim under bearing.
For reference, with used gears sets the rule of thumb is set the pattern up on the non-driven surface because it will typically have better resolution of the pattern (less worn). Don't worry too much about setting up a text book contact pattern as doing so may move the contact contact portion to a different part of the tooth, and could cause a quiet diff to become a noisey one. What you should focus on is putting backlash to where it was before you took the carrier out of the housing. If you didn't measure it before go on yukon or randy's website and pull up the chart and go with the used gear backlash for your R&P which will have to be the best you can get. It being centered on the tooth from heel/toe doesn't really matter as much as it being centered from face to flank(top and bottom). I wouldn't even run a contact pattern for new bearings, just verify backlash. New pinion bearings shouldn't effect pinion depth enough to make a difference they are manufactured very precisely. |
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The backlash was at .0065" to .007". Whoever replaced the trac lock clutches also replaced the carrier bearings, becuase they were Timken, all the rest were Koyo, yet. Then they reused the fat factory shims on the carrier again.
I did not check the pattern before, but I did think about doing it, just didn't have marking compound. I think I'll loosen up the backlash a smidge and check it again. |