4L80E Sprag Clutch 1991

Owners of early 4L80E trucks, from the first 1991 Chevy and GMC 2500 and 3500 pickups and Suburbans onward, plus anyone rebuilding the TH400 the 4L80E grew out of, find this part when second gear starts slipping or goes missing. It is a new BorgWarner intermediate sprag, part number 06763AM, with 34 elements, made to fit the sprag-style direct drums used since 1964. One part, one job: restore the one-way hold that gives you second gear.

How the intermediate sprag works in the 4L80E and TH400

GM built the 4L80E by putting an overdrive section in front of a gear train that is TH400 at heart, so the intermediate sprag works the same way in both. The sprag sits on the hub of the direct clutch drum, surrounded by an outer race that the intermediate clutch grabs. In first gear nothing holds that race, and the sprag just spins. On the 1-2 shift the intermediate clutch applies, the race stops, and the angled sprag elements jam between race and hub, holding the sun gear stationary. On the 2-3 shift the direct clutch applies and drives the drum forward, and the elements tilt back to freewheel. Because one part only has to apply while the sprag releases on its own, the shift is quick and smooth. When elements wear or flip over, that hold is lost and second gear goes with it.

Signs the sprag has failed

• Engine flare between first and second, often worse with a load or hot fluid
• No second gear at all; the truck pulls in first, then lands in third
• Intermediate clutches that come out black or glazed on teardown
• Metal on the magnet and a scored outer race or drum hub
• On early 4L80E trucks, a combination of second-gear slip and a soft first that hints the low roller is tired too

Diagnose before you tear it down

Second-gear complaints are not always mechanical. A shift solenoid stuck on or off, or a bad speed sensor signal, can make the computer skip or mis-time second, so check those circuits with our 4L80E shift solenoid guide and the speed sensor symptom guide. Next, put a gauge on line pressure, since low pressure burns the intermediate clutch first and only then takes the sprag with it. Our Sierra 2500 4L80E problems guide covers the full list of early-truck faults worth ruling out.

Fitment

Listed for the 4L80E and 4L85E from 1991 on and for the TH400 and 3L80 with non-roller, sprag-style intermediate drums, going back to 1964. That covers the early 1991-to-1995 2500 and 3500 Chevy and GMC trucks, Suburban 2500, full-size vans and Hummer H1, as well as later units. The one catch is drum style: some TH400 drums use a roller-type intermediate clutch and this sprag will not fit them. Look at your old part, match the 06763AM number if you can read it, or send us your year and VIN. If your early truck also needs a new low roller, the 1991-95 low roller and sprag set gets you both in one order. More early parts are on our 4L80E collection page.

Install notes

• Clean and inspect the outer race and drum hub; replace either one if it is pitted or worn to a shine.
• Pre-lube the sprag with ATF and set it in the same orientation as the original.
• Test by hand before installing the drum: it should lock in one direction and spin freely in the other. If it turns both ways, flip it.
• Replace the burnt intermediate frictions; the 1991-1995 4L80E overhaul kit and a clutch module cover the early units.
• Fit a new filter, refill with Dexron VI and check the level at operating temperature.

Will this fit a TH400 as well as a 4L80E?

Yes, when the TH400 uses a sprag-style intermediate drum. The listing covers non-roller drums from 1964 on. A TH400 with a roller-type intermediate clutch needs different parts.

Is this the same sprag used in later 4L80E transmissions?

It is listed for 4L80E and 4L85E from 1991 on, so it is not limited to early trucks. It is the 34-element design, which the maker lists as replacing earlier 16-element versions.

Does this include the low roller clutch?

No, it is the intermediate sprag only. If your early 4L80E has no first gear in Drive as well as a second-gear problem, look at the 1991-95 set that includes the low roller.

How do I know second gear loss is the sprag and not a solenoid?

Scan for codes and test the shift solenoids and speed sensors first, then check line pressure. If the electrical side and pressure are good and second still flares or is missing, the sprag or intermediate clutch is the likely cause.

Which fluid should go back in after the repair?

GM lists Dexron VI for the 4L80E in later owner manuals. Fill, run the engine, and check the level hot in Park.

• 4L80E Shift Solenoid Symptoms and Replacement: A and B Diagnosis
• 4L80E Input/Output Speed Sensor Symptoms
• 4L80E Sierra 2500 Common Problems and Fixes
• 4L80E Common Problems and Fixes: The Six Failures That Actually Come Through the Door