Dropout differentials, also known as third members, can be readily identified by their removable front center section. The ring and pinion gear set in a dropout diff is contained within a carrier assembly that can be removed or dropped out for easy access. The iconic Ford 9-inch is a dropout or third member type of differential and GM, Toyota, and many other brands also offer dropout diffs.
Toyota dropout-style diffs consist of the 7.5” rear, 8” rear, 8” high pinion, 8” clamshell, 7.5”, 8.5”, T100 IFS, and numerous 9”, 9.5”, and 10” offerings. In the Mopar world dropout differentials are called banjo-style diffs because someone thought the assembly, when pictured with an axle shaft, had the look of the infamous stringed musical instrument. The Chrysler 8.75” is the automaker’s most popular dropout-style diff. Of course, Dana manufactures a number of dropout style diffs that appear in vehicles across numerous brands. In some circles a front-loading dropout-type diff is known as a pig-style diff. While on the subject of slang, our friends across the pond call the ring gear a “crown wheel” … hey, as long as we’re on the same page it’s all good.
Perhaps the main inherent advantage of a dropout diff is easy gear swaps. Since the gear case center section can be unbolted and removed, all the ring and pinion gear installation and tedious setup can be done away from the vehicle on a workbench. It’s more comfortable and access to, and applying leverage on, the key components is much easier.
Carrier differentials have a cover on the backside of the pumpkin that is unbolted to gain access to the ring and pinion gears and other internal workings of the diff. GM’s 10-bolt and 12-bolt differentials are common examples of carrier-style diffs, which may be referred to as Salisbury differentials by those who speak the Queen’s English.
Carrier-type differentials are more popular and they have some strengths when compared to a dropout diff. Troubleshooting is one. Looking for broken or worn parts in a carrier diff is as easy as removing the back cover where in a dropout you have to commit to a full gear case removal to see what’s going on. It should be noted that some custom aftermarket dropout diffs have rear inspection covers to address this concern.
Knowing what dropout and carrier-type differentials are and a general idea how they work will help you make more informed installation decisions as you have the knowledge and vocabulary to talk straight with your mechanic.