4L80E Planetary 1991

Lost third gear and Reverse in a 4L80E-equipped Chevrolet or GMC 2500 or 3500, Suburban 2500, Express or Savana van, or Hummer H1? Or a truck that skips second and bangs straight from first into third? Both trails lead to the same rotating part: the direct clutch drum and the intermediate sprag that rides on it. Although this item is filed under our planetary listings, it is not a planet carrier. It is a used GM 4L80E direct drum with its sprag, built for 1991 and newer 4L80E transmissions in both 2WD and 4WD trucks, referenced to GM part number 24209311 and interchange U34555EK. It was professionally inspected before it was listed.

What the direct drum and sprag do in a 4L80E

The 4L80E main geartrain comes from the Turbo 400 family, and the direct drum sits in the middle of it, behind the forward clutch and ahead of the center support. Its clutch pack applies in third, fourth and Reverse. Apply oil reaches the drum through the center support, sealed by piston rings that ride inside the drum bore. The outside of the drum hub carries the intermediate sprag. In second gear the intermediate clutch grounds the outer sprag race, so the sprag locks the drum and the sun gear it drives against reverse rotation. On the 2-3 shift the direct clutch applies, the drum turns forward, and the sprag simply freewheels.

That makes this one part responsible for three different gears, which is why it is so often the root of a 4L80E complaint after heavy towing or a power upgrade. Sonnax notes that sprag damage and rollover are common in high-torque 4L80E and Turbo 400 builds, and TransGo warns that runaway boost pressure can break the direct drum and the case.

Symptoms that point to the direct drum or sprag

• No third gear and no Reverse, or a long delay before either engages
• Slip or flare on the 2-3 shift, or no fourth gear, with burnt direct frictions in the pan
• First to third shift with no second, or a slipping second gear (intermediate sprag)
• Maximum line pressure with a second-gear start and the MIL on, from a ratio or slip code
• Steel shavings or broken sprag pieces on the magnet

How to confirm it before you order

Pull codes first. A gear ratio or TCC slip code can come from worn direct clutch sealing, but the same codes also come from a weak pressure control solenoid or a sensor fault, so read our 4L80E common problems and fixes guide and check line pressure before tearing down. If pressure is good and third and Reverse are both gone, the direct circuit is the suspect. Sonnax explains that wear in the drum bore from the center support rings lets third and Reverse apply oil exhaust, causing direct clutch failure and delayed or missing third and Reverse. Once the unit is apart, check the bore, the piston, the clutch pack and the sprag: it must lock in one direction and spin freely in the other. Low line pressure from a failing EPC is covered in the 4L80E EPC solenoid symptoms guide.

Fitment

This drum is listed for 1991 and newer 4L80E units in 2WD and 4WD configurations, including the GM heavy-duty pickups, Suburban 2500, full-size vans and H1 that used the 4L80E. Even within that range, confirm the configuration before you buy: compare the drum you remove (piston style, clutch count and sprag) and quote GM 24209311 or U34555EK when you ask. If you are not sure, send us your year and VIN and we will check it before it ships. The rest of the hard parts and kits are on the 4L80E transmission collection.

Install notes

• The transmission has to come out; the direct drum sits behind the forward clutch and is reached after the pump and front section are removed
• Install new center support seal rings and fresh direct clutch frictions and steels; a 4L80E clutch module and a 4L80E overhaul gasket and seal kit cover those
• Check sprag freewheel direction by hand before the drum goes in; installed backwards it will not hold second
• Air check the direct clutch through the center support before final assembly
• Fill with Dexron VI ATF and check the level hot, as GM's owner manual describes

Is this a planetary gear set?

No. It is a used GM 4L80E direct clutch drum with its intermediate sprag. It is grouped with our planetary listings, but the part you receive is the drum assembly.

Which 4L80E years does it fit?

It is listed for 1991 and newer 4L80E transmissions in 2WD and 4WD trucks, referenced to GM 24209311 and U34555EK. Match it against your old drum or send year and VIN to confirm.

My truck has no 3rd and no Reverse. Is this the fix?

Losing both gears together points at the direct clutch circuit: the drum, its piston, the frictions or the center support rings. Confirm line pressure first, then inspect the drum bore and clutch pack when the unit is apart.

Does it come with clutches inside?

Plan on installing fresh direct clutch frictions, steels and seals during the rebuild rather than relying on used friction material.

What fluid should I use after installing it?

Dexron VI ATF. GM's owner manuals for these trucks describe checking the level hot at normal operating temperature, so top it off after a test drive.

• 4L80E Common Problems and Fixes: The Six Failures That Actually Come Through the Door
• 4L80E Pressure Control (EPC) Solenoid Symptoms
• 4L80E Silverado 2500 Common Problems and Fixes
• 4L80E Express Van Common Problems and Fixes