4L80E Planetary 1997, remanufactured and ready to install. Fits the 4L80E. Ships fast from the USA.
If your heavy-duty GM truck or van with a 4L80E has started to hesitate before it pulls into Drive, slips in every forward gear while Reverse still feels solid, or came apart with burnt forward clutch plates, the forward drum is the housing at the center of that job. This listing is a genuine GM 4L80E and 4L85E forward drum of the molded piston type, the configuration used from 1997 on. It has been cleaned and inspected and comes as the drum shown, with the internal gear teeth at its open end. It suits 1997 and later 4L80E units in Chevrolet and GMC 2500 and 3500 pickups, Suburban 2500, Express and Savana vans, and the matching 4L85E.
The 4L80E is a Turbo 400 style three-speed geartrain with an overdrive section bolted on the front. Power leaves the overdrive planetary through the ring gear cut into the front of this drum, so the drum spins with overdrive output at all times. Inside it sit the forward clutch piston, its return springs, and the forward clutch pack. When the valve body sends apply oil through the sealing rings into the drum, the piston squeezes the pack and locks the drum to the forward clutch hub, which turns the mainshaft and the rear gearset. The forward clutch is applied in every forward gear, so any leak at the piston or the sealing ring bore shows up as slip in first, second, third and fourth alike.
The 1997-up molded piston has its sealing lips bonded onto the piston rather than using separate loose lip seals. Builders favor it because the earlier aluminum piston has a reputation for cracking under heavy load, which is one reason the later drum is in demand for towing trucks.
Low pressure produces the same slip, so put a gauge on the line pressure port first. A sticking or failed pressure control solenoid can drop pressure in every range, and our 4L80E pressure control solenoid guide walks through that test. If pressure is good in Drive and you still have slip only in the forward ranges, the forward circuit is the problem. On the bench, air check the forward clutch through the case passage, then inspect the drum bore where the sealing rings ride. A ridge you can catch with a fingernail means the drum is done. The broader picture of 4L80E failures is in 4L80E common problems and fixes.
The listing covers 1997 and later 4L80E and 4L85E transmissions with the molded piston forward drum, and it carries interchange number 34554EA. The 4L80E changed internally over its run, so pull your old drum and confirm it uses the molded piston before you order. A 1991 to 1996 unit with the earlier piston setup is not a simple swap. Compare the snap ring grooves, the clutch lug count and the gear teeth against the photos, or send us your year and VIN and we will check it. Every 4L80E part we carry is on the 4L80E parts page.
| Fits | 4L80E 1997 |
| Part type | Planetary |
| Condition | Remanufactured |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The front of this drum carries the overdrive ring gear, so it is part of the overdrive gearset as well as the forward clutch housing. What you receive is the 1997-up molded piston forward drum shown in the photos.
Not as a direct swap. This is the 1997 and later molded piston drum. Earlier units used a different piston setup, so send your year and VIN or photos of your drum and we will tell you what fits.
Plan on installing new forward clutch frictions, steels and sealing rings. A used clutch pack should never go back into a rebuilt 4L80E.
That pattern points at the forward clutch circuit, which includes this drum, its piston and the sealing rings. Check line pressure first so you do not miss a pressure control fault.
DEXRON-VI. GM lists 7.7 quarts for the 4L80-E in the 2008 Express owner manual. Check the level with the fluid at operating temperature.
