* The 8.5″ axle was used on vehicles up to 1999. The 8.6″ was used on vehicles 1999 and up. Since 1999 was the transition year, some vehicles received the 8.5″ while others received the 8.6″. The easiest way to tell the difference is by looking at the brakes. All 8.6″ axles have disc brakes and 8.5″ have drums.
* The factory 8.5″ carrier when installed in a factory 8.5″ axle uses Timken bearing part # LM501349 and race part # LM501314. The inner diameter of the bearing is about 1.625″ and the outer diameter of the race is about 2.890″.
* The factory 8.6″ carrier when installed in a factory 8.6″ axle uses Timken bearing part # LM603049 and race part # LM603012. The inner diameter of the bearing is about 1.780″ and the outer diameter of the race is about 3.060″.
* Nowadays, most locker manufacturers produce parts only for the 8.6″ and include properly sized bearings to retrofit them into the older 8.5″ axles. Therefore, the inner diameter of the bearings for these parts will be about 1.780″ and the outer diameter of the race will be about 2.890″. This same logic also applies to differential carriers, but it is important to note that the parts are BACKWARD compatible only. That’s to say that the newer 8.6″ differential cases when used with the appropriate sized bearings and races can install into older 8.5″ axles. As of this writing, there are no bearing and race combinations that allow an 8.5″ carrier or locker to install into an 8.6″ axle. When retrofitting an 8.6″ carrier (or a locker or a spool or any device that replaces the carrier) into an 8.5″ axle, it uses Timken bearing part # LM102949 and race part # LM102911.
OEM Part Number