Three ways to confirm what's in your axles: diff tag, axle code on door sticker, or count ring/pinion turns. Always confirm before buying gears.
Before ordering gears, identify what you currently have. Methods, fastest to most reliable:
1. Door jamb sticker / build sheet: most XJs have an axle code on the door jamb sticker. Common codes:
2. Differential tag (most reliable): a stamped metal tag on the diff cover bolts identifies ratio and date. Format varies but you'll see '3.55', '4.10', etc., plus a tooth count like '41-13'. The tooth count is ring/pinion teeth — divide ring by pinion to get the ratio.
3. Ring/pinion turn count: jack up one wheel, mark the driveshaft and one tire, rotate the tire EXACTLY one revolution while counting driveshaft turns. The number of driveshaft turns is approximately your gear ratio. (For 4-wheel-drive, ratio = 2 * driveshaft_turns / 1 tire turn because the diff splits.)
The code on the jamb is fast; the tag is more reliable since previous owners may have regeared. If gears are aftermarket and the tag was lost, do the turn count.
Confirm front and rear ratios match before regearing. Mixed ratios are common after a partial regear by a PO — buying new gears for one axle without the other is a hassle and slightly damages the t-case chain.
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.