GM 10-Bolt & 12-Bolt Lockers and Posi Carriers

A GM rear end is identified three ways before a carrier can be chosen: the ring-gear size (7.5, 8.2, 8.5 or 8.875 in), the axle spline count, and the gear-ratio range the carrier was built for - get any one of the three wrong and the carrier does not fit, however right the other two are. This page pulls together 24 in-stock traction carriers and spools for GM 10-bolt and 12-bolt rear ends from Eaton, PowerTrax, Yukon Gear and Axle and Strange Engineering, from $193.02 to $857.99: 15 clutch-type limited slips (Eaton Posi, Yukon DuraGrip and PowerTrax GRIP LS), 5 Detroit Truetrac carriers, 1 locker and 3 full spools. Every spline count and ratio range quoted below comes from that product’s own listing - including the two listings that contradict themselves or each other, which are flagged where they appear rather than smoothed over. Every order over $200 ships free.

OUR GM 10-BOLT & 12-BOLT PICKS

Product	Spec (from the product listing)	Price	Why it is here
Lock Right Differential GM 8.5 78-88 28 Spline	Locker, 28 spline, steel, GM 8.5 in, listed for 1978-88, PowerTrax Lock Right (per listing)	$451.99	The only product on this page sold as a locker in its own listing, and the cheapest full traction device here. Its listing states the axle (GM 8.5), the spline count (28) and the year range (1978-88) - and no gear-ratio range, so ratio is not a filter on this one the way it is on every carrier below.
GRIP LS - Gm 12 Bolt Car 4.1	Limited slip, 30 spline, 4.10 ratio and up, steel, GM 12-Bolt 8.875 in, PowerTrax GRIP LS (per listing)	$538.19	The 12-bolt car pick for deep gears: this is the one 12-bolt limited slip here whose listing starts at 4.10 and up, which is exactly the carrier-break question most 12-bolt buyers get wrong. If your ratio is milder than 4.10, this is not your carrier - the Eaton Posi units below cover the lower ranges.
Detroit Truetrac - GM 7.625 10-Bolt	Detroit Truetrac carrier, 28 spline, 3.23 ratio and up, steel, listed for 7.5 / 7.6 in, GM 10-Bolt (per listing)	$642.99	The small 10-bolt entry: the listing itself states 7.5 / 7.6 in even though the title says 7.625, and its ratio floor (3.23 and up) is higher than the 8.5 units - read both numbers before assuming a 7.5 carrier behaves like an 8.5 one.
Eaton Posi - GM 8.5 10-Bolt 28-Spline	Eaton Posi limited slip, 28 spline, 2.73 ratio and up, steel, GM 8.5 in 10-Bolt (per listing)	$750.99	The mainstream 8.5 pick: the broadest ratio coverage on the page (2.73 and up covers most street and strip gear choices) in the most common spline count. Its 30-spline twin is also on this page for cars that have already upgraded axles.
Eaton Posi - GM 8.2 BOP	Eaton Posi limited slip, 28 spline, 3.36 ratio and up, steel, GM 8.2 in BOP (per listing)	$857.99	The ceiling of the page, and the trap it exists to disarm: this 8.2 is the Buick/Olds/Pontiac pattern, not the Chevrolet 8.2 - the two share a ring-gear size and a name and nothing else. The Chevrolet 8.2 Posi is a different listing on this same page, $107 cheaper.

STEP ONE: NAME YOUR AXLE - RING-GEAR SIZE FIRST

8.5 in 10-bolt (9 of 24) is the deep shelf here, in 28- and 30-spline versions of nearly everything: the Lock Right locker at $451.99, both PowerTrax GRIP LS units, both Yukon DuraGrips, two Detroit Truetracs and both Eaton Posi spline counts. 8.875 in 12-bolt (6 of 24) splits car and truck in the listings themselves: the GRIP LS above is a car unit for 4.10 and up, Eaton’s truck Posi (1961-80 fullsize truck per its listing) covers 2.76 to 3.42, and the two same-titled Eaton Posi car units are separated in Step Three. 8.2 in 10-bolt (4 of 24) is three different axles wearing one size: Chevrolet 1964-82, Chevrolet 1955-64 in 17 spline, and the BOP pattern - each has its own Posi on this page and none of the three swaps with another. 7.5 / 7.625 in 10-bolt (2 of 24) is Truetrac only, in 26- and 28-spline. The last 3 of 24 are Strange full spools - two 12-bolt and one 8.5 - covered in Step Four. Questions before you order? Call 213-549-4279 (Mon-Fri, 9am-5pm PT) and we will read the listing with you.

STEP TWO: COUNT YOUR SPLINES

Spline count is the axle shaft’s tooth count where it enters the carrier, and it is a hard filter: a 28-spline carrier cannot take a 30-spline axle. The counts on this page are 17 spline (one listing only - the 1955-64 Chevrolet 8.2 Eaton Posi at $775.99), 26 spline (the 7.5 Truetrac for 3.08 and down), 28 spline (the majority - most 8.2 and 8.5 units, both GRIP LS spline options sit either side of it), 30 spline (the 12-bolt standard here, plus the upgraded-axle 8.5 units) and 33 spline (the 12-bolt Truetrac at $856.99 and the lightweight Strange spool - both assume aftermarket 33-spline axles). If you do not know your count, pull an axle and count, or read it off the axle itself - do not guess it from the year, because mid-run changes and past axle swaps make year-based spline guesses the most common wrong order in this category.

STEP THREE: THE CARRIER BREAK - RATIO RANGE DECIDES THE REST

GM carriers are built for a ratio range, and a ring gear outside that range does not bolt up correctly. The ranges the listings state: 8.5 in - nearly everything here is 2.73 and up (both Eaton Posi counts, both GRIP LS, both DuraGrips, both Truetracs), so the 8.5 break is the simple one. 7.5 in - the break matters: the 26-spline Truetrac is 3.08 and down, the 28-spline is 3.23 and up. 8.2 in - the Chevrolet 1964-82 Posi and the DuraGrip are 3.08 and up, the 1955-64 unit is 3.90 and down, and the BOP Posi is 3.36 and up. 12-bolt - the widest spread: truck Posi 2.76 to 3.42, DuraGrip truck HD 2.76 to 3.42 (see the note in Step Five), GRIP LS car 4.10 and up, Truetrac 33-spline 4.10 and up. And the page’s one genuine puzzle: two listings carry the identical title “Eaton Posi - GM 8.875 12-Bolt 30-Spline” at the same $750.99 - they are different part numbers (19554-010 and 19556-010) with different stated ranges, 3.08 to 3.90 and 3.73 and up, which overlap between 3.73 and 3.90. If your ratio falls in that overlap, call us and we will confirm the right part number with Eaton before you order - the page will not pretend the two are one product.

STEP FOUR: LOCKER, POSI, TRUETRAC OR SPOOL - WHAT EACH ONE IS

Clutch-type limited slip (15 of 24) - Eaton Posi, Yukon DuraGrip and PowerTrax GRIP LS: both wheels driven, with the clutch pack allowing the speed difference a street corner needs. This is the default street and street/strip choice on the page. Detroit Truetrac (5 of 24) - Eaton’s gear-driven limited slip line, here for 7.5, 8.5 and 12-bolt; note one of the two 8.5 Truetracs is listed as a front application (at $749.99) while its near-twin at $696.99 is the rear - the titles differ by a few words, so check which end of the truck you are buying for. Locker (1 of 24) - the PowerTrax Lock Right, the only unit here whose listing calls it a locker: locked drive to both wheels, the drag and off-road choice, with the manners that implies on the street. Full spool (3 of 24) - Strange steel spools that tie both axles together permanently, including a lightweight Pro Race version; a spool is a race part - both wheels turn together always, corners included - and the listings here state 4 Series for both 12-bolt spools, while the 8.5 spool’s listing states no series. Mini spools, which replace only the side gears inside an open carrier, are a different and cheaper part and are deliberately not on this page - they are in the parent collection below.

AN HONEST NOTE ON WHAT IS NOT HERE

Two listing problems are printed, not hidden. First, the Yukon DuraGrip truck HD unit above is titled and filed as a GM 12-Bolt part, but its own feature line reads “8.5 in” - the part number (YDGGM12T-3-30-1) and the 2.76 to 3.42 range match the 12-bolt truck application, but if that contradiction matters to your build, call us and we will confirm with Yukon before you order. Second, the overlapping Eaton Posi pair in Step Three. Also deliberately not here: the GM 8.6 in Truetrac listed for the 2010-up Camaro, the 9.5 in and 14-bolt units, and every Ford, Dana and Mopar carrier in the wider range - different axles, however close the names sound. Twelve GM mini spools, the open 8.5 carrier case, and the shims, install kits and limited-slip oils that support these carriers all live in the parent collection too; this page is traction carriers and full spools only. No listing on this page states a torque or horsepower rating, so none is printed here - if a power figure decides your choice, that number has to come from the manufacturer.

QUESTIONS BUYERS ASK US

How do I tell a 10-bolt from a 12-bolt? Count the bolts on the rear cover - that is where the names come from. Then measure or look up the ring-gear size, because “10-bolt” covers four different axles on this page alone (7.5, 7.625, 8.2 and 8.5 in) whose carriers do not interchange. Cover count gets you the family; ring-gear size, spline count and ratio range get you the carrier.

28 or 30 spline - can I just upgrade? The carrier and the axle shafts change together: a 30-spline carrier needs 30-spline axles. On the 8.5, this page stocks both counts in Eaton Posi, GRIP LS and DuraGrip form, so the choice is really about whether you are also buying axles. If your 28-spline axles are staying, buy the 28-spline carrier.

Will a posi carrier fit my gears? Only inside its stated ratio range - that is the carrier break in Step Three. Find your ratio first (the axle tag, the door sticker’s axle code, or count ring and pinion teeth during the swap), then match it against the range printed on the listing, not against the axle name alone.

Is the Chevrolet 8.2 the same as the BOP 8.2? No. Same ring-gear size, different housing and carrier pattern - Buick, Oldsmobile and Pontiac built their own 8.2. The page stocks a Posi for each, titled accordingly; ordering the Chevrolet unit for a BOP rear end is a return waiting to happen.

Posi or spool for a street car? A spool locks both wheels together permanently, which is exactly right on a drag strip and hard work everywhere else - it scrubs tyres in corners and stresses axle shafts on the street. The clutch-type posi units on this page exist for cars that turn corners on pavement; the spools are here for cars that mostly do not.

Shopping the wider range? Browse the full Drivetrain collection, read our guides on the News & Builds blog, or see the page that came before this one: LS Swap Oil Pans for GM Muscle Cars & Trucks.

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