Yukon Gear High Performance Replacement Gear Set For Dana 30 in a 4.27 Ratio
A 4.27 front gear set is usually bought for one reason: the rear axle already runs 4.27 and the front has to match it. That happens on CJ, Scout and early Bronco builds where the rear was regeared first, or where the owner wants a bit more than a 4.11 without spinning the engine as hard as a 4.56 on the highway. The Yukon Gear & Axle YG D30-427 is a new 4.27 ring and pinion for the standard-rotation, low-pinion Dana Spicer 30 front axle.
The pinion in this axle sits below the centerline and drives a 7.20 in. ring gear the same direction as a rear axle, with a 26-spline pinion and 10 ring gear bolts per Yukon's listing. Preload is set with a solid shim pack rather than a crush sleeve. At 4.27, the pinion turns 4.27 times per wheel revolution. Against a 3.73 that is about 14 percent more torque at the tires; against a 4.11 it is only about 4 percent, so this ratio is less about a big performance jump and more about landing exactly on the rear axle ratio or fine-tuning engine rpm for a given tire size and transmission.
Confirm the rear ratio first by counting teeth or reading the tag; a 4.27 front with a different rear ratio will fight the transfer case. Then confirm the front axle is the standard-rotation Dana 30 and not a reverse-cut YJ-style axle or a TJ and late XJ short-pinion unit. Our Dana 30 problems and rebuild cost guide covers wear points to inspect while the axle is apart, and regearing after bigger tires helps you compare 4.11, 4.27 and 4.56 for your setup.
This set shares its axle with the other standard-rotation Dana 30 gears we carry, and catalogs list it for the CJ5, CJ6, CJ7 and Scrambler, International Scout and Scout II, early Bronco and Jeepster Commando with the Dana 30 front. It is not for the YJ front, the TJ and late XJ short-pinion axle, or the JK and JL reverse-rotation fronts. Older axles were not always built the way the catalog says, so match the pinion position and axle tag, or send us your year and VIN. If 4.27 is not the number you need, the same axle takes our Yukon Dana 30 4.11 set or the deep Yukon Dana 30 5.38 set.
A 4.27 ring gear mounts on the 3.73-and-numerically-higher Dana 30 carrier. If your axle came with 3.54 or lower gears, plan on a Dana 30 3.73-up open carrier or a locker built for that carrier break.
Use all new bearings, races and a pinion seal; the USA Standard ZK D30-F master kit is a lower-cost option for this axle. Yukon's chart lists a 0.065 in. starting pinion shim, 12-15 in-lb of new pinion bearing preload and 60 ft-lb on the bearing caps. Mark the bearing caps so each goes back on its own side, set depth, preload and backlash in that order, and confirm the contact pattern on both the drive and coast sides. Fill with 75W-90 GL-5 gear oil, drive gently through break-in and change the oil early.
| Brand | Yukon Gear & Axle |
| Part number | YG D30-427 |
| Fits | Yukon Gear High Performance Replacement Gear Set For Dana 30 in a 4.27 Ratio |
| Type | Final Drive Gears |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes. In 4WD the front and rear are locked together through the transfer case, so a 4.27 front needs a 4.27 rear. Mismatched ratios cause binding and can damage the transfer case.
No. Non-Rubicon TJs use a short-pinion Dana 30 that takes a different gear design, and Rubicons have a Dana 44 front. This set is for the standard-rotation Dana 30.
No. A 4.27 ring gear needs the Dana 30 carrier for 3.73 and higher ratios. A 3.54-and-down axle needs a new carrier or a 3.73-up locker.
Most buyers pick it to match a rear axle already geared 4.27. It sits about 4 percent deeper than 4.11, a middle ground for tire sizes where 4.56 spins the engine too fast on the highway.
All carrier and pinion bearings and races, shims, the pinion seal and ring gear bolts. A master overhaul kit covers these. Inspect the axle tube seals and u-joints while it is apart.
