8L90 Clutch Drum, used and ready to install. Fits the 8L90. Ships fast from the USA.
This is a used GM 8L90 1-3-5-6-7 clutch drum, interchange number 334554B: the aluminum four-clutch version with 36-tooth steels, eight lugs on top and the tin reluctor ring fitted. It is the drum shops go looking for when an 8L90 out of a Silverado, Sierra, Tahoe, Yukon, Escalade, Corvette, Camaro or Express van comes apart with a cracked housing, a scored piston bore or a burned pack, and the truck had been slow to go into Drive or flaring on the 2-3 shift before it quit.
The 8L90 gets eight forward ratios from four gear sets and five clutches. The 1-3-5-6-7 clutch is named for the gears it holds, so it is applied in five of the eight forward ranges. In GM bulletin 16-NA-019 it applies on the 2-3 and 4-5 upshifts, releases on the 1-2, 3-4 and 7-8 upshifts, and is the clutch learned on the Neutral-to-Drive garage shift. Note the naming: GM's bulletins call this pack C3, while GEARS Magazine and most parts catalogs label the same drum C1. Go by the gear numbers and you will not order the wrong piece. The drum carries the plates, apply piston and return spring, and it is fed through sealing rings, so any leak at a ring land or piston bore lowers apply pressure and the control module chases it with longer fill times until it runs out of adapt.
GM bulletin 20-NA-187 gives a clean test for the Drive side: after the vehicle sits 8 to 24 hours, watch input speed on a scan tool with your foot on the brake and shift to Drive. If input speed is not at zero within 3 seconds, run the C3 Drive clutch learn. If the learn does not fix it, GM's next step is to tear down and inspect the 1-3-5-6-7 clutch plates and seals. Before that teardown, rule out valve body problems; Sonnax has measured line pressure over 415 psi on worn 8L90 valve bodies against a design peak near 315 psi, which can crack castings and break drums. Our 8L90 valve body symptoms guide and 8L90 common problems and fixes walk through both.
The listing covers 8L90 units from 2015 on. The catch is drum capacity: GEARS Magazine reports this drum was built in a four-clutch and a five-clutch design depending on application and year, and you identify yours by the code beside the QR code on top of the drum (8L90A or 8L90B). This one is a four-clutch drum, so count the friction plates in your old drum, check the lug count and steel tooth count, or send us your year and VIN before ordering. The smaller 8L45 uses its own drum; see the 8L45 1-3-5-6-7 clutch drum. Everything for this family is on the 8L90 and 8L45 collection page.
| Fits | 8L90 |
| Part type | Clutch Drum |
| Condition | Used |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Both names describe the same part. GM's bulletins call the 1-3-5-6-7 clutch C3; GEARS Magazine and parts catalogs call it C1. It applies in 1st, 3rd, 5th, 6th and 7th.
Read the code next to the QR code on top of your drum and count the friction plates. This drum is the four-clutch version, so match it to a four-clutch original or send us your year and VIN.
It can be. GM's 20-NA-187 test allows 3 seconds for input speed to reach zero. If a C3 learn does not fix a longer delay, GM directs inspection of the 1-3-5-6-7 clutch plates and seals.
No, it is a used GM drum. Inspect the bushing, ring lands and piston bore and air-check it before installation.
New frictions, steels and seals for this pack, a filter and pan gasket, and fresh GM-specified fluid. Then run the adaptive learns.
