Seals the 6L80/6L90 3-5-Reverse and 1-2-3-4 clutch drum so you can air-test each apply circuit and pinpoint the hairline cracks and leaking piston seals that cause slipping and no-reverse.
The most expensive 6L80 rebuild is the second one. A 3-5-R or 1-2-3-4 drum with a hairline weld crack looks perfect on the bench, goes back into a 2006-and-up Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro or CTS, and the no-reverse or slip-in-fifth complaint returns. This WCH003 billet tester plugs the drum so you can put shop air into each apply circuit and find the leak before anything is reassembled.
In the transmission, the 1-2-3-4 and 3-5-R pistons are fed through sealing rings on the pump cover. On the bench there is nothing sealing those feed holes, so air you blow in just escapes. The tester stands in for the pump cover: it drops into the drum, seals the bores, and gives you a marked port for each circuit. Put the air nozzle to one port and that piston should stroke and hold. A healthy circuit holds pressure. A hiss, a piston that will not stay applied, or bubbles at the weld seam point to a cracked casting or a cut or rolled lip seal. It is machined from 6061 aluminum billet so the sealing faces stay flat, and it weighs 2.4 pounds.
If the truck sets P0776, P2715 or P2723, or has lost reverse, first rule out the valve body. Our 3-5-R clutch failure guide explains how a sticking regulator valve mimics a cracked drum, and the 6L80 Escalade shift problems guide walks through shift-quality diagnosis on the full-size platform. Once the drum is out, the GM procedure is soap on the weld, thumb over the air bleed, and air into the 3-5-R feed; this tool turns that into a sealed, repeatable test. Getting the drum out square is easier with the T-47781AC drum removal tool.
Listed for GM 6L80 and 6L90 transmissions, 2006 and up, in Chevrolet, GMC and Cadillac cars and trucks, and it tests both the 1-2-3-4 and 3-5-R circuits. Part number WCH003. It does not test the 4-5-6 clutch. If you are not sure which unit you have, send us the year and VIN. We also carry a lower-cost input drum air check tester, so compare both before ordering. The rest of our tools and parts for this transmission are in the 6L80 collection.
| Fits | GM 6L80 and 6L90 (2006-up Chevy, GMC, Cadillac cars and trucks) |
| Tests | 1-2-3-4 clutch drum and 3-5-Reverse clutch drum apply circuits |
| Material | CNC-machined 6061 aluminum billet |
| Method | Seals the drum for compressed-air leak and crack testing at each port |
| Weight | 2.4 lb |
| Part number | WCH003 |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The 1-2-3-4 and 3-5-Reverse clutch drum in the GM 6L80 and 6L90, 2006 and up. It does not test the 4-5-6 clutch.
Bubbles or hissing at the weld seam mean a cracked housing, which GM says must be replaced. A leak at the piston usually means a cut, rolled or hardened lip seal.
GM describes covering the bleed passage with your thumb and spraying air into the 3-5-R feed hole. The tester seals every port so the test is repeatable and you can check each circuit separately.
Yes. A sticking 3-5-R regulator valve causes the same no-reverse and slip complaints, so check codes and pressures before tearing the unit down.
Use regulated shop air in short bursts, enough to stroke the piston and listen for leaks. Follow your service manual for the specific air-check procedure.
