4L70E Sprag Clutch 1986-2014, new and ready to install. Fits the 4L70E. Ships fast from the USA.
When a 4L70E truck or SUV idles in Drive with the engine revving and goes nowhere, or slips and shudders pulling away with a trailer behind it, one of its two one-way clutches is the usual suspect. This listing is a Borg Warner set with both of them: the 29236AM forward sprag and the 28571AM low roller clutch. The pair is listed for 1986-2014 700R4, 4L60E, 4L65E and 4L70E transmissions, so it covers the 2006-2013 Silverado, Sierra, Tahoe, Yukon and Trailblazer SS 4L70E units as well as the earlier members of the family.
A one-way clutch locks in one direction of rotation and spins free in the other, which lets the transmission change gears without two holding devices fighting each other. The 4L70E has two. The forward sprag, inside the input housing, carries torque from the forward clutch into the input sun gear in first, second and third, and overruns when the transmission goes into fourth or the driver lifts off the throttle. The low roller clutch, at the back of the gear train, holds the reaction carrier so first gear has something to push against. Neither one uses oil pressure to hold, which is why they fail by wear and heat rather than by leaks.
The 4L70E puts more torque through these parts than a light-duty 4L60E. It sits behind the 5.3L and 6.0L V8s in full-size trucks and the Trailblazer SS, and these are vehicles that tow. Launch torque goes straight through the forward sprag and the low roller clutch every time the truck pulls away from a stop, so a sprag that rolls over under that load is a common no-drive failure.
Transmission Digest describes a road test that isolates each one-way clutch by applying a clutch that holds the same part. In the 700 family, D and 3 apply the overrun clutch alongside the forward sprag: if a launch shudder or 2-3 flare is present in Overdrive but gone in D or 3, the input sprag is not holding. A truck that moves in manual Low but not in the other forward ranges points to the low roller clutch. Delayed or missing engagement can also come from pump, seal and line pressure problems, so read our 4L70E delayed engagement guide and the 4L70E common problems guide before tearing the unit down.
The set is listed for 1986-2014 GM 700R4, 4L60E, 4L65E and 4L70E. That range spans nearly three decades of running changes, including different input housings and sprag styles. Before installing, lay the old sprag and roller clutch next to the new ones and compare width, element count and inner race fit. If your unit has been rebuilt with aftermarket hard parts, match what is in it now, not what the build sheet says. Send us your year and VIN if anything is unclear, and browse every part for this unit on the 4L70E parts page. Our interchange guide explains which hard parts carry across the family.
Hold the assembled input housing and turn the input sun gear by hand before it goes back in the case: it must lock in one direction and freewheel in the other, and a sprag installed backward gives no drive. Inspect both races; a pitted or brinelled race will destroy the new sprag quickly, and a roller clutch race with flat spots should be replaced. To check a roller clutch cage, compare how far a worn cage rotates in the housing against a new one. A failed sprag leaves metal throughout the unit, so this is a rebuild job: install the set with a 4L70E overhaul kit, inspect the input drum for scoring, flush the cooler, and fill with Dexron VI.
| Fits | 4L70E 1986-2014 |
| Part type | Sprag Clutch |
| Condition | New |
| Brand | Borg Warner |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is listed for 1986-2014 700R4, 4L60E, 4L65E and 4L70E transmissions, which includes the 2006-2013 GM trucks and SUVs that use the 4L70E. Compare your old parts side by side before installing, since the family had several running changes.
Two one-way clutches: the 29236AM forward sprag that goes in the input housing, and the 28571AM low roller clutch that holds the reaction carrier in first gear.
That pattern usually points to the low roller clutch, because manual Low applies a clutch that holds the same part the roller clutch normally holds. Confirm with a full diagnosis before pulling the transmission.
The forward sprag is inside the input housing and the low roller clutch is at the rear of the gear train, so the transmission must come out and be disassembled. Because a failed sprag sheds metal, most shops do a full overhaul at the same time.
Dexron VI automatic transmission fluid is the GM specification for the 4L70E.
