How to weld a differential
Write-up and pictures courtesy of Andrew Farkas
Disclaimer: By performing this procedure you understand that your vehicle is for race use only, and shall be deemed unsafe for street use. The owners of 614streets.com, nor I will be held responsible for any damages or harm done caused for any reason after this procedure.
Assuming you have the knowledge and resources to perform this procedure I will begin this DIY with the entire third member removed from the rear end. The first thing you’re going to do is remove the differential housing from the carrier by unbolting the shim locks and removing the bearing caps with shims.
Next you’re going to loosen the top hat bolts in a star method in effort not to cause any stress or bend the top hat itself. Pull the top hat off the differential with the gear to expose all of the spider gears inside.
Remove the spider gears and all internals of the differential while paying attention to the way they were arranged inside the housing. It was necessary to remove the entire ring gear to remove the retaining pins, however you may not have to in your case. Make sure to clean the spider gears by generously dousing them with a brake cleaner in order to keep from contaminating the welds with dirt and oils.
When welding the spider gears, you want to make a small bead in the valley between the teeth. Do not make this too tall due to clearance issues when reassembling your differential. Once you have made one pass, skip one valley and then weld the next, then skip two and weld the third. Here is how it should turn out:
After welding, cool the gears preferably in oil and then assemble the differential with all the pins and gears while checking for proper fitment. You don’t want the gears to be so loose that they slap, however if the pins will not go in because the beads is be too big, slightly grind the beads down with a file or grinder. Once everything is back in there torque the top hat bolts again. For my own reassurance I decided to bead the spider gears to my actual housing from the outside. At this point you’re finished, reinstall your ring gear and properly setup and install your diff as you normally would. Enjoy your now welded differential!
With this setup it can be very harsh on your rear drive train because you are now transferring stress through your housing and on your pins and axles. I does not dramatically increase tire wear but it does promote tire chirping on slow, tight radius turns. Again, because there is a chance something may break, and it is strongly advised that you avoid street use.