In last month's issue, we followed Zip Products technician Keith Wilhelm as he assembled one of the company's heavy-duty Dana 36 differentials. This time around, we'll detail the process of installing the diff and matching cover in our '96 C4 project car. Although most elements of the job should fall well within the comfort zone of a competent mechanic, access to both a lift and a task-specific spring-compression tool is strongly recommended. Lacking all of the foregoing (especially the competence part), we outsourced the project to our Vette-savvy friends at AntiVenom in Seffner, Florida. Follow along now as we cover the highlights of the installation.
Now that you've spent a few hours swapping in your new heavy-duty differential, you'll want to make sure you break it in properly. Failure to do so can leave you with a diff that whines, chatters, and otherwise impersonates your mother-in-law. Fortunately, Zip includes detailed break-in instructions with every unit it ships, so doing the job right is simply a matter of reading them and doing as you're told.
After filling the diff with fluid and traction additive (remember: no synthetics), take the car out on the road and check for noise. If none is present, continue to drive at a steady 45 to 65 mph for 30 miles, avoiding heavy acceleration and, if at all possible, stopping. Let the rear cool completely, then repeat the process. After three of these 30-mile driving cycles, the rear should be fully broken in. Have your rear alignment specs checked by a qualified tech (preferably one who's worked on Corvettes before), and you're ready to enjoy your new heavy-duty differential. As for us, we'll have driving impressions and drag-strip numbers for you in an upcoming issue.