Shop All Transmission Parts →
A customer orders a locker for a Dana 44, it arrives, they pull the cover, and the ring gear will not bolt up flush. The part is not defective. They ordered the wrong side of the carrier break. It is the single most common ordering mistake on lockers and limited slips, and it is entirely avoidable once you understand why it exists.
Why One Axle Needs Two Carriers
The pinion always sits in the same place in the housing. To get a numerically higher ratio (deeper gears like 4.56 or 4.88), the pinion gets smaller. To keep the smaller pinion meshing at the right spot on the ring gear, the ring gear has to be thicker. A thicker ring gear needs its mounting flange to sit in a different spot relative to the carrier bearings.
Manufacturers solve that with two carrier designs for one axle: one for the lower numerical ratios and one for the higher. The dividing line is the carrier break. Everything on your side of it fits; everything on the other side does not.
Common Carrier Breaks
| Axle | Low Series | High Series |
|---|---|---|
| Dana 30 | 3.54 and down | 3.73 and up |
| Dana 35 | 3.54 and down | 3.73 and up |
| Dana 44 | 3.73 and down | 3.92 and up |
| Dana 60 | 4.10 and down | 4.56 and up |
Many other axles have breaks too, and a few common ones use a single carrier across the usual ratio range. The rule is the same everywhere: the product listing will name a ratio range. If your ratio is inside it, you are good. If it is not, it will not fit — no exceptions, no shims that fix it.
How to Confirm Your Ratio
Do not trust a window sticker or a forum post about what your trim came with. Axles get swapped and regeared. In order of reliability:
- Read the ring gear. Pull the cover. The tooth counts are stamped on the ring gear, like 41-11. Divide: 41 / 11 = 3.73. This is the only answer that cannot be wrong.
- Check the axle tag. Many axles have a metal tag under a cover bolt with the ratio stamped on it. Tags get lost or moved during regears, so treat it as likely, not certain.
- Count driveshaft turns. With the vehicle on stands, transmission in neutral and one tire held, turn the other tire two full turns and count driveshaft turns. That gives you the ratio within reason. Good for a quick check, not for ordering between 3.54 and 3.73.
More detail on tags and codes is in our guide to finding your axle ratio.
Spline Count Is the Second Filter
Once you are on the right side of the break, the locker still has to match your axle shaft spline count. A Dana 30 front is usually 27 spline from the factory; some upgraded shafts are 30 spline. Dana 44 rear axles have come in 30 and 32 spline versions depending on year and model. Dana 60 fronts are commonly 30 or 35 spline. Pull a shaft or check your build sheet. If the shafts are aftermarket, count the splines on the shaft itself.
Regearing Across the Break
This is where people lose money. If you have 3.73s in a Dana 44 and want 4.56s, you are crossing the break. Your existing carrier, whether it is open, limited slip or locked, will not take the new ring gear. You need a new carrier no matter what.
That makes the regear the perfect time to install a locker. The carrier bearings are coming off anyway, the setup labor is already being paid for, and the locker just becomes the new carrier. Buying a locker for your current 3.73s and regearing next year means buying a second locker.
So the order of operations is simple: decide the final gear ratio first, then buy a locker for that ratio, then install both together. Our regear guide walks through picking the ratio for your tire size.
What About Ring Gear Spacers?
For some axles there are thick ring gears or ring gear spacers that let a low-series carrier accept a higher ratio. They exist for good reasons, mostly when a particular locker is only made in one series. They also add a joint between the ring gear and carrier, require longer bolts, and add one more thing to get exactly right. If a carrier exists in the correct series, use it.
Order Checklist
- Axle model confirmed (housing casting, not just vehicle)
- Final ring and pinion ratio decided and read off the ring gear
- Axle shaft spline count confirmed
- Front or rear, and for Dana 44 front, regular or reverse rotation
- Installation kit or master overhaul kit for the bearings and shims
Setup procedure is covered in our backlash and pinion depth guide.
Reverse Rotation and Front Axles
One more filter catches people on front axles. Some front axles are reverse rotation (high pinion), where the ring gear is on the opposite side and the gear teeth are cut for the other direction. Dana 44 and Dana 60 fronts both come in standard and reverse rotation versions depending on the vehicle. Ring and pinion sets are rotation-specific. Most lockers are not, but some installation kits and carriers differ, so check before ordering. If the pinion enters the housing above the axle centerline, you likely have a reverse rotation front.
Shop by Carrier Series
- Eaton ELocker4 — Dana 44 front, 30 spline, 3.73 and down
- Eaton ELocker4 — Dana 44 front, 30 spline, 3.92 and up
- Eaton Detroit Locker — 35 spline, 4.10 and down
- Eaton Detroit Locker — Dana 60, 35 spline, 4.56 and up
- Eaton ELocker4 — Dana 60, 35 spline, 4.10 and down
- Eaton Truetrac — 27 spline front, 3.54 and down
- Dana 30 front limited slip, 27 spline, 3.73 and up
Order It Right the First Time
Lockers and limited slips are listed by axle, spline count and ratio range so you can match your carrier series. Transmission and transfer case parts are at our sister store.
Shop Lockers and Diffs → Core Transmission Parts →FAQ
Can I shim a 3.73-and-down carrier to fit 4.10 gears?
No. Carrier break is about where the ring gear mounts, not bearing preload. Shims will not move it far enough. You need the correct series carrier, or on some axles a purpose-made ring gear spacer.
Do I need a new carrier if I go from 3.55 to 3.73 on a Dana 30?
Yes. That crosses the Dana 30 break at 3.54 and down versus 3.73 and up.
Where is the ratio stamped?
On the ring gear itself, usually as two tooth counts such as 41-11. Divide the first by the second to get the ratio.
Does the carrier break matter for a lunchbox locker?
No. A lunchbox locker goes inside your existing carrier, so it only cares about spline count and axle model. The break matters when you replace the whole carrier.