What This Seal Actually Does
This is a rear differential oil seal, not a wheel seal — it sits behind the pinion yoke on Meritor RS-21-145 and RR-20-145 carriers and keeps gear lube from migrating out along the pinion shaft. When it goes, you'll see oil on the yoke, sometimes slinging onto the driveshaft, and if it's bad enough the diff starts running low and you get gear whine or worse.
Meritor used this basic carrier design across a long stretch of trucks, roughly 1980 through current production, so this seal shows up on a lot of iron — Freightliner, Kenworth, Peterbilt, International, you name it, as long as they've got the RS-21-145 or RR-20-145 axle under them. The carrier housing bore and pinion shaft diameter are what matter, not the truck badge on the hood.
Why These Numbers Cross
A1-1205Z2730 is Meritor's number and CR30009 is the aftermarket equivalent — Chicago Rawhide made a lot of these seals over the years and that CR prefix stuck around as a reference point even on parts made by other manufacturers now. National (NS100263), Federal-Mogul, and a few others all built to the same seal ID/OD and lip design because Meritor's carrier housing bore didn't change dimensions even when they updated internals.
The numbers in the table — A1205Z2730, R945003, 100263, 72910 — are the same physical seal from different catalogs and different eras of numbering. Where guys get burned is assuming any 'rear seal' fits any tandem axle. Double reduction axles, different carrier castings, and some of the older single-reduction units use a different bore size entirely, so a seal that looks identical can still be off by a few thousandths.
Before you order, pull the old seal and read the number stamped or molded into the metal case if it's still legible. If it's rusted out or shredded, the RS/RR-20-145 or -21-145 stamp on the carrier housing itself is your safest bet, or just give us your axle model and we'll match it to CR30009 or tell you it isn't.
Ordering From PartStop
We keep CR30009 in stock at the Tacoma counter for guys who need it same-day — log truck broke down on I-5, waste hauler leaking in the yard, whatever the story is. Local pickup means you're not waiting on a seal that costs sixty bucks to hold up a truck earning money.
Ship nationwide too, and this is a small enough part that shipping doesn't kill the deal. Comes with our standard 6+ month warranty, which covers manufacturing defects — not seals that get torn up because the yoke was pounded back on wrong or the housing bore's scored.
At $59 it's cheap insurance against a comeback. Just confirm the carrier model and pinion bore against your VIN or the old seal before you check out — we'll help you match it if you're not sure, better to ask now than to R&R a diff twice.
A1-1205Z2730 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to A1-1205Z2730. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | A1205Z2730, R945003, 100263, CR30009, 72910, NS100263, 30009, 2590277C |
Frequently asked questions
Does A1-1205Z2730 fit my 2015 Freightliner with a Meritor tandem?
Probably, but confirm the axle model first — you want RS-21-145 or RR-20-145 stamped on the carrier housing. Meritor used a bunch of different rear axle setups even within the same truck year, so the axle tag matters more than the truck's model year.
Is CR30009 the same seal as NS100263?
Yes, National's 100263 and CR30009 cross to the same Meritor application — same bore, same lip design, built to fit the A1-1205Z2730 spec. Different label, same seal. Still worth checking your old part's number if it's readable, just to rule out a double-reduction carrier variant.
How do I know if it's the pinion seal and not something else leaking?
Oil showing up specifically around the yoke, sometimes slung onto the driveshaft or U-joint, points to the pinion seal. If it's leaking from the cover gasket or axle tube ends instead, that's a different repair — worth crawling under with a rag before you order parts.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.