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Gearing

When regearing the Jeep it is often necessary to change the gear carrier; this is because as the pinion tooth count goes down it often gets smaller, making it necessary to move the ring gear closer. Most commonly used light axles have two carriers available, a thick and a thin depending upon the application. The crossover between needing one carrier or the other is commonly referred to as the 'carrier break'

This list shows some of the common axles used with Jeeps. Although it represents many axles, it is by no means all-inclusive.

For XJ-specific axle information, see this page.

Front Axle Options

Axle	What Jeeps have it?	Carrier Breaks		Miscellaneous info
Dana27	Front Axle, early CJ	3.73 & down	3.92 & up
Dana30	Front Axle - CJ, TJ, XJ, WJ, YJ, ZJ	3.54 & down	3.73 & up	CJ have passenger-side pumpkin TJ, XJ, WJ, YJ, ZJ have driver's side pumpkin XJ 84-99 D30s are high-pinion XJ 00-01 D30s are low-pinion All YJ D30s are high-pinion All TJ D30s are low-pinion
Dana44	Front (low pinion) - Rubicon TJ - Rubicon LJ Later model SJ Front	3.73 & down	3.92 & up	(Above: XJ rear Dana44, front is similar)
	Other vehicles			See the exterior section of my 'Future Mods' page for more information on axle swaps into Cherokee and Wrangler-sized Jeeps

Rear Axle Options

Dana35	Rear Axle YJ (all), XJ (most 84-91, all w/ABS post-91), Most TJ	3.31 & down	3.55 & up	(Above: YJ Dana 35. Note oval cover, rounded bottom portion)
Chrysler 8.25"	XJ rear, non-ABS post-91 91-96 models had 27-spline axleshafts. Starting in late 96, available in non-ABS Cherokees with the heavier-duty 29-spline shafts. My Cherokee (built after March 96) had the earlier 27-spline	2.45 & down *	2.56 & up	(Above: XJ 8.25 Note the oval-shaped cover and flat cast 'lip' that differentiates the 8.25 from the Dana 35) * Since the highest XJ gear is the 3.07 included with most manual-shift Cherokees, the numerically lower 8.25" carrier isn't seen in our applications
Dana44	CJ rear thru 1975 Some 1986 CJ-7 and -8 rear Some 1987-89 XJ Cherokee rear (most common in 1987 w/towing package, very rare in later models) Some TJ rear Front (low pinion) & Rear - Rubicon TJ Common Front and Rear Swap, all models	3.73 & down	3.92 & up	(Above: XJ Dana44) (Above: 1973 CJ-5 Rear Dana44)
Dana60	Common Rear-Axle Swap	4.10 & down	4.56 & up	Good source - '79 F250, they have a Fullfloating D60 rear. Some early 80's Dodge pickup or vans have 35 spline Fullfloating shafts. Also, lots of early 80's Ford trucks have semi-float 60's that are 35 spline. Downside is, those axle use shafts that are retained by C-clips (c-clip eliminators can be corrected with C-clip eliminators). Some Ford vans had a D61 - it sounds closely related but apparently isn't a very well-supported axle option.
AMC20	CJ7 rear (two-piece axleshafts) 1976-83 CJ-5 rear (two-piece axleshafts) SJ rear (one-piece axles) MJ Comanche, with one-piece axle shafts. Available in at least the early (84-87) MJ; or possibly just the '86 Metric Tonne version. The 1-piece axleshaft is preferred and stronger than the CJ version which is prone to failure by spinning the keyed hub.	2.73 & down	3.07 & up	AMC20 under a 1986 MJ Comanche. Picture provided by Pete M from NAXJA
Ford 8.8	Ford Explorer/Navajo; Mercury Mountaineer			95 and newer had 31 spline & disk brakes. This is a great axle to use and you can find it very easily, plus the disc brakes are a nice mod in and of themselves. '96 and newer have 4.10 gearing available. Check M.O.R.E. for parts to make this swap into any XJ, YJ, TJ, etc. The Ford 8.8 is slightly narrower than the D35, measuring 59.75" WMS-WMS vs 61.25" for the D35-eqipped XJ (WMS is wheel-mounting surface). This means each side is going to be 3/4" narrower. While the narrower rear can mean tighter turns on trails, it also means the tires may make contact with the inner fenderwells unless you use spacers or rims with less backspacing

While it's extremely important to keep the front and rear ratios the same, you may notice that some front and rear ratios are off slightly but this is okay. I've heard the variance can be up to 1%, but I wouldn't recommend taking it too far. As an example, 4.10 and 4.11 are commonly used from the factory in 4-cyl Jeeps. 3.55 and 3.54 are often found as well; the reason for the minor difference is that the tooth count between ring and pinion isn't the same in different axles but it isn't a concern as far as the mismatch of numbers. .

The gear manufacturer also plays a bit part in the strength of the axle; some manufacturers build their junk in China, and quality apparently doesn't translate correctly. Here are a few thoughts on the matter:

• You can keep costs down by installing a locker at the same time as the gears are changed. While the parts are more expensive, you pay for labor only once, and in many cases you won't have to buy a new open carrier that will be removed with the locker anyway.
• You can regear one end at a time if your budget is tight. **HOWEVER** make sure that you remove the front driveshaft if you do this, to prevent severe damage to the drivetrain. (the availability of this option may vary by vehicle)
• Don't use someone else's used gears unless your Jeep is a trail-only rig. I did, and learned the hard (and expensive) way that used gears are a pain to properly set up, and they are 99.99% guaranteed to be noisy.
• Stay away from some of the companies offering lifetime warranties. Genuine Gear is one of these; they offer a no-questions-asked lifetime warranty on their gears, but I've talked to enough installers to keep me away from those. The quality is shady, the gears are known as "GenuWHINE" by many, and a lifetime warranty on broken gears doesn't include the damage that a broken gear can do inside the pumpkin or the labor costs to remove and replace...

  I've heard the gears recommended in roughly this order; your mileage may vary:

  • Spicer
  • Superior
  • Yukon
  • US gear

  then

  • Precision
  • Richmond
  • Sierra
  • Value Gear
  • Genuwhine

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created: Dec 30, 2003