6L50 Overhaul Kit

If you are rebuilding the GM 6L50 out of a Cadillac CTS, STS or SRX, a V6 Camaro or a Pontiac G8, this is the seal and gasket set that every circuit in the case depends on. It is built for the 6L50 (RPO MYB) and the closely related 6L45 (RPO MYA), and it is the kit to buy when the transmission is coming apart for leaks, delayed engagement or a pressure-loss slip. It is an overhaul kit without pistons: gaskets, lip seals, sealing rings and O-rings. Friction plates, steel plates and molded pistons are not in the box.

What the overhaul kit does in a 6L50

The 6L50 is a clutch-to-clutch six-speed. There are no bands and no one-way sprag doing the shifting in most gears; instead the control module times one clutch releasing against another applying, and every one of those clutches is applied by oil that has to stay inside its circuit. The sealing rings on the shafts and drum hubs carry that oil from the case and pump into the rotating drums, and the lip seals and O-rings keep it behind each piston. When a ring wears its groove or a seal shrinks with heat, apply pressure bleeds off, the clutch fills late, and the module sees the shift take longer than it expects. A fresh set of every ring, seal and gasket in the unit puts the hydraulic side back to factory tightness during a rebuild.

Symptoms this kit addresses

• External leaks at the pan, the front pump seal, the rear output seal or the case connector
• Delayed engagement into Drive or Reverse after the vehicle sits, a sign oil is draining back out of a clutch circuit
• Slips or flares on shifts that get worse as the fluid gets hot
• Harsh or late shifts as the control module tries to compensate for slow clutch fill
• Limp mode with clutch or ratio-related codes after a slip event

How to confirm it before buying

Start with the fluid. The 6L50 has no dipstick and is set with a level plug at 86-122 F, so a low unit is easy to miss; our 6L50 fluid type and capacity guide covers the procedure. Then pull codes and check line pressure before condemning the clutches, because a stuck pressure control solenoid or a valve body fault can produce no-move and slip complaints with a perfectly good clutch pack. The 6L45 and 6L50 limp mode guide lays out those checks. On all-wheel-drive Cadillacs, a grinding no-move is often worn output shaft splines at the transfer case, not anything inside the gearbox. If the unit truly needs to come apart, this kit is the base of the job.

Fitment

The kit is listed for the 6L50 (6L50E, RPO MYB) and 6L45 (6L45E, RPO MYA) from 2007 on. Applications on the list include the Cadillac CTS 2008-2016, CTS Sport Wagon and CTS Coupe, STS 2006-2013, SRX and XLR 2006-2009 4.6L V8, Chevrolet Camaro V6 2009-2015, Pontiac G8 V6 2008-2010, Chevrolet Colorado and GMC Canyon, and BMW 1, 3, 5 and 6 Series and Z4 with the six-speed automatic. Two cautions. First, GM reduced the oil volume of the 1-2-3-4 and 3-5-R clutch pistons by 20 percent starting with the 2008 model year, and the 2008-and-later pistons do not back-service 2006-2007 units. This kit has no pistons, so reuse your originals or buy the correct year's parts. Second, a vehicle can be built with a 6L45, 6L50 or 6L80 depending on engine, so check the RPO on the glovebox or door label, or send us your year, model and VIN. More parts for this unit are in the 6L50 parts collection.

Install notes

• Mark the 1-2-3-4 and 3-5-R pistons as you remove them so they go back in the same drum; do not mix early and late parts.
• Inspect every sealing ring groove. A ring is only as good as the groove it rides in, and a stepped groove will leak with a brand-new ring.
• Lube lip seals with ATF or assembly gel and size the shaft sealing rings before the drums go on so they do not get cut on install.
• Check the pump while it is out. A scored pump body costs more pressure than any seal; the 6L50 pump for 2006-2018 is the replacement if yours is worn.
• Air-check each clutch circuit through the case before installing the valve body. GM upper valve bodies are unique by RPO, so a swapped one causes its own no-reverse complaint; the remanufactured 6L50E valve body is built for the MYB.
• Fill with DEXRON-VI only and set the level hot at the plug. Run a fast-learn adapt with a scan tool after the rebuild so the module relearns clutch fill times.

Does this 6L50 overhaul kit include frictions, steels or pistons?

No. It is a gasket and seal kit without pistons: gaskets, lip seals, sealing rings and O-rings. Frictions, steels and pistons are sold separately.

Will it fit a 6L45 as well as a 6L50?

Yes. The kit is listed for both the 6L45 (RPO MYA) and 6L50 (RPO MYB) from 2007 on. Check the RPO on your vehicle label or send us your VIN if you are not sure which unit you have.

My 6L50 is a 2007. Does the 2008 piston change matter?

It matters for pistons, not for this kit. GM reduced the 1-2-3-4 and 3-5-R piston oil volume for 2008 and the later pistons do not back-service 2006-2007 units. Keep your original pistons with their original drum.

What fluid does the 6L50 take after the rebuild?

DEXRON-VI. The level is set at the check plug with fluid temperature between 86 and 122 F; a dry unit after a rebuild with the cooler flushed can take ten to twelve quarts.

Do I need a relearn after installing the kit?

Yes. Clear adapts and run a fast-learn with a scan tool so the control module relearns clutch fill times on the fresh seals, then road test through every gear.

• 6L45 Limp Mode: Causes and How to Diagnose It
• 6L50 Fluid Type and Capacity