6L45 Clutch Drum 2007

A 6L45 that has lost reverse, flares on the 2-3 shift, slips in fifth, or now hesitates to move forward at all after a long run of slipping is often down to one hard part: the drum that carries the 1-2-3-4 and 3-5-Reverse clutches. This listing is a new replacement 1-2-3-4 / 3-5-R clutch drum for the GM 6L45, reference D45555B, with a 7-3/4 in outside diameter, built for 2007 and later units. It cross-references to GM 24260890 and industry number D135733A. It is the drum only, so plan on fresh frictions, steels and seals for the packs it carries.

What the 1-2-3-4 / 3-5-R drum does in a 6L45

The 6L45 is the light-duty member of GM's six-speed rear-drive family, found behind smaller engines in Cadillac CTS and STS models, the V6 Camaro and BMW 1, 3 and 5-Series cars that call it the GA6L45R. Five clutches give it six forward gears. Two of the busiest live in this drum. The 1-2-3-4 clutch is applied in first through fourth, and the 3-5-Reverse clutch is applied in third, fifth and reverse. Apply oil from the TEHCM (the valve body and control module in one unit) is fed through sealing rings into the drum, where it pushes each piston against its pack. If the drum cracks, its welds leak, or its sealing ring surfaces wear, that apply oil bleeds away and the clutch never reaches full holding pressure.

Symptoms of a failing 1-2-3-4 / 3-5-R drum

• No reverse, or a reverse that engages late, bangs in or slips
• Harsh or flaring 2-3 shift and a slip or flare into fifth
• Slipping in first through fourth, or a no-forward condition once the 1-2-3-4 pack burns
• Burnt fluid with friction material and metal in the pan
• Pressure control solenoid performance codes such as P0776 or P0777 on the 3-5-R circuit, often with the transmission dropping into limp mode
• The same complaints returning soon after a rebuild that reused a cracked drum

How to confirm it before you buy

A 3-5-R code does not condemn the drum by itself. On the GM six-speeds the clutch regulator valve bore plug can leak at its retainer and set the same code with a healthy drum, so start with the electrical and hydraulic checks in our 6L45 limp mode diagnosis guide. If the fluid is burnt and the pan carries friction debris, the problem is mechanical. With the unit apart, air-check the 3-5-R and 1-2-3-4 feed holes with the drum assembled, cover the bleed, and coat the welds with soapy water. Bubbles at a weld mean the drum is done. Our 3-5-R clutch failure breakdown walks through the full test and GM's bulletin on cracked housing welds in this family.

Fitment

This drum is listed for the 6L45 from 2007 on, with the 7-3/4 in outside diameter. GM revised the 1-2-3-4 piston, piston housing and 3-5-R piston in this family for the 2008 model year on the larger units, and early drums are not guaranteed to match, so a 2006 unit can need a different drum; that earlier version is our 2006 6L45 clutch drum. Measure your old drum's OD, compare it against the photo, and check the RPO on the vehicle's service parts label (MYA is the 6L45). If you are unsure, send us the year and VIN before ordering. Browse every part we carry for this unit on the 6L45 parts page.

Install notes

• Inspect the sealing ring surfaces and bushings that ride against the drum. New sealing rings are a must; worn ring lands on the mating shaft will leak no matter how good the drum is.
• Install new inner and outer piston seals and check that every snap ring is fully seated and indexed. A mis-indexed snap ring is a known cause of 3-5-R complaints.
• Air-check both pistons on the bench before the drum goes in, then set clutch clearance to the factory spec for each pack.
• Replace the frictions and steels for both packs. A 6L45 master rebuild kit covers the soft parts in one box.
• Flush the cooler and lines so old clutch debris does not return, then fill with Dexron VI and set the level hot.
• Clear the adapts and run a full relearn with a capable scan tool before judging shift quality.

Which clutches does this 6L45 drum hold?

The 1-2-3-4 clutch and the 3-5-Reverse clutch. Between them they are applied in first through fifth and reverse, which is why a failed drum causes such a wide spread of complaints.

Will a 2007-up drum fit my 2006 6L45?

Not reliably. GM revised the pistons and housing in this area early in the run, so match your old drum's outside diameter and design, or send us the year and VIN so we can confirm before you order.

My 6L45 has no reverse and a P0776 code. Is the drum bad?

Not always. A leaking clutch regulator valve bore plug in the TEHCM can set the same code. Check fluid condition and pressure first; burnt fluid with clutch debris points to the drum and clutch pack.

What should I replace with the drum?

New frictions and steels for both packs, piston seals, sealing rings and any worn bushings. Most builders install the drum as part of a complete rebuild with a master kit.

What fluid and relearn does the 6L45 need afterward?

Dexron VI, with the level set hot per the factory check procedure. Then reset the transmission adapts and complete a relearn drive so the TCM learns the new clutch volumes.

• 6L45 Limp Mode: Causes and How to Diagnose It
• 6L80/6L90 3-5-R Clutch Failure
• 6L50 Fluid Type and Capacity
• 6L80 No Reverse Fix