Clamps the 1-2-3-4 and 3-5-Reverse drum on GM 6L50, 6L80 and 6L90 units so it lifts out square instead of cocking in the case.
Searching for a way to get the reverse drum out of a 6L80 without fishing for it? On the GM 6L50, 6L80 and 6L90 there is no stand-alone reverse drum. Reverse is applied by the 3-5-R clutch, which lives in the same housing as the 1-2-3-4 clutch, and that combined housing is what this T-47781AC style clamp is built to grab. It is the tool you want in hand for the no-reverse, delayed-reverse and 2-3 flare repairs that send 2006-and-up Silverado, Sierra, Tahoe, Yukon, Escalade, Camaro and Corvette owners to a rebuild shop.
The 6L80 is a clutch-to-clutch six-speed. Power from the turbine shaft enters this housing, and its two clutch packs feed the gearsets: the 1-2-3-4 clutch for the first four gears, the 3-5-R clutch for third, fifth and reverse. Both pistons are fed through sealing rings on the pump cover, so the housing sits directly behind the pump and has to slide over that stator shaft on the way in. GM's bulletin on cracked housings describes the factory replacement as a complete assembly with pistons, seals, clutches and bearing already inside, which tells you how much weight is in your hands when you lift a loaded unit. There is no lip or flange designed for gripping it.
The tool closes on the housing body and locks with a switch in the handle. Lift straight up and the housing stays square in the case bore; on the way back in you can hold it level with one hand and turn the turbine shaft with the other until the clutch plates find their hubs.
The same complaints come from a sticking 3-5-R regulator valve in the valve body, so start with codes and pressure checks. Our 6L80/6L90 3-5-R clutch failure guide sorts valve body faults from housing faults, and the 6L80 Camaro problems guide covers the cold 2-3 flare caused by trapped air rather than broken parts. Once the housing is on the bench, GM calls for soap on the weld area and compressed air into the 3-5-R feed hole with the bleed passage covered; a 6L80/6L90 drum leak tester seals the ports so that test is quick.
Listed for the GM 6L50, 6L80 and 6L90, 2006 and up, in Cadillac, Chevrolet and GMC rear-drive cars and trucks. The part number is T-47781AC, the same designation as the GM tool it replaces. It is made for the 1-2-3-4/3-5-R housing only, not the 4-5-6 clutch at the back of the case. If you are unsure which unit is under the vehicle, send us the year and VIN. Parts for the rest of the job are in the 6L80 collection.
The tool is stainless steel, measures 7.9 x 7.1 x 10.4 inches, weighs 2.55 pounds and carries a 1-year warranty.
| Part number | T-47781AC |
| Fits | GM 6L50, 6L80, 6L90 transmissions, 2006-up |
| Vehicles | Cadillac, Chevrolet, GMC rear-drive cars and trucks |
| Serves | 1-2-3-4 drum and 3-5-Reverse drum removal and installation |
| Material | Stainless steel |
| Dimensions | 7.9 x 7.1 x 10.4 in, 2.55 lb |
| Warranty | 1 year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. Reverse is applied by the 3-5-R clutch, which shares one housing with the 1-2-3-4 clutch. That combined housing is what this tool clamps.
Yes, it is listed for the 6L50, 6L80 and 6L90 from 2006 up. It is not intended for the 4-5-6 clutch housing at the rear of the case.
If the diagnosis points to the 3-5-R clutch or a cracked housing weld, the housing has to come out, and this tool keeps it level so you do not cut the pump cover sealing rings or drop it in the case.
GM warns that a 2008 6L80 complete housing installed in a 2007 or older unit may cause a 2-3 flare or 3-5-R clutch distress. Match the housing to your model year.
Lube the sealing rings and soak new frictions in DEXRON VI, the fluid GM specifies for the 6L80 and 6L90.
