4L80E Sprag Clutch 1991-2001, remanufactured and ready to install. Fits the 4L80E. Ships fast from the USA.
If your 1991 to 2001 Chevy or GMC 2500 or 3500, Suburban 2500, Express, Savana or Hummer H1 moves fine with the shifter pulled down to 3 but sits there and revs in Drive, the overdrive one-way clutch is the first suspect. This listing is a remanufactured GM assembly: the overrun clutch drum with the overdrive sun gear and the sprag already installed. Because the three pieces come together, you are not hunting for a used drum, a separate sun gear and a loose one-way clutch, then hoping they match.
The 4L80E has three one-way clutches, and this is the one at the very front of the gear train. It sits inside the overrun clutch drum and locks the overdrive planetary so the input turns the gearset 1:1 through 1st, 2nd and 3rd. When the overdrive clutch applies for 4th, the sun gear is held and the one-way clutch simply freewheels. The detail that matters for diagnosis is the overrun clutch: with the lever in the overdrive position the one-way clutch carries that front section by itself, and the overrun clutch only joins in when a manual range is selected. Transmission Digest points out that this is why plow and tow trucks driven in overdrive kill the part, and that overheating can melt its plastic cage and finish it off quickly.
The road test does most of the work. Check the fluid level hot first, then drive the truck in Drive and again in manual 3. If manual 3 drives and Drive does not, the front one-way clutch is the likely failure, because manual 3 brings in the overrun clutch to hold the same gearset. If the truck will not move in any forward range, look further back at the forward clutch or the low roller clutch instead, and gauge line pressure before tearing in. Our 4L80E common problems guide walks through the overdrive failure and pressure checks, and the Sierra 2500 problems guide covers why heavy-duty work trucks see it most.
This assembly is listed for 4L80E units from 1991 through 2001. GM revised the overdrive section over the production run, so later units and some 2000 to 2001 transmissions may carry a different one-way clutch style. Pull your old drum and compare the sprag, sun gear spline and drum before ordering, or send us your year and VIN and we will check it. If you only need the drum and sun gear and plan to reuse a good sprag, the 1991-2000 overrun housing with sun gear is the bare version. Everything else for early units is on our 4L80E parts page.
| Fits | 4L80E 1991-2001 |
| Part type | Sprag Clutch |
| Condition | Remanufactured |
| Brand | GM |
| 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 the complete assembly: the overrun clutch drum with the overdrive sun gear and the one-way sprag installed. The bare drum and sun gear without the sprag is sold separately as the 1991-2000 overrun housing.
That is the classic sign of a failed overdrive one-way clutch. In manual ranges the overrun clutch holds the same gearset, so the truck still moves. In Drive the one-way clutch works alone, so if it has failed you get no drive or a big flare in 1st through 3rd.
It is listed for 1991 through 2001 units. The overdrive one-way clutch design changed over the production run, so compare your old assembly or send us your year and VIN before ordering for a later truck.
Use Dexron VI ATF, which replaces the earlier Dexron specifications for these transmissions. GM lists roughly 7.7 quarts for a 4L80E pan and filter service; fill after a rebuild to the hot level on the dipstick.
Overrun clutch frictions and steels, the drum sealing rings, and the pump and overdrive bushings if worn. Many rebuilders also replace the low roller clutch and intermediate sprag at the same time because the parts are inexpensive and the labor is already done.
Heavy loads in overdrive, plowing and overheating are the usual causes. In the overdrive position the one-way clutch carries the front gearset by itself, and heat can melt its plastic cage.
