6T30 Overhaul Kit 2016-2019

When a 2016-2019 GM compact or small crossover with the 6T30 or 6T35 starts dripping ATF, takes a second or two to grab Drive on a cold morning, or begins to slip once it is hot, the rubber and Teflon inside the transmission are usually the root of it. This is the third-generation 6T30/6T35 overhaul kit, kit number KP52900CCX, for 2016-2019 units. It contains the gaskets, lip seals, O-rings, sealing rings and small rubber parts needed to reseal the transmission during a rebuild. It does not include pistons.

What the overhaul kit does in a 6T30

The 6T30 is the lightest member of GM's 6T family, built for small four-cylinder engines. It shares the basic layout of the 6T40: two planetary gearsets, five hydraulically applied clutches and a side-mounted control solenoid valve body. Every clutch is applied by a piston fed through a chain of sealed passages from the pump to the drum. The kit replaces the sealing parts in that chain, so the pressure the control module commands is the pressure the clutch actually receives. On a high-mileage unit those parts have been through years of heat cycles, and a rebuild that reuses them tends to come back.

Symptoms this kit is meant to fix

• External ATF leaks at the converter housing, side cover, pan or case seams
• Delayed engagement into Drive or Reverse when cold that improves as it warms
• Pressure loss and slipping after high mileage, with flare on upshifts
• Slip or loss of Reverse, third or fifth with P0776, where the 3-5-R piston and wave plate also need inspection

How to confirm a reseal is what you need

A 6T30 has no dipstick, so check the level hot at the level set plug before anything else. An overfill can push fluid out the vent and look like a seal leak, and an underfill causes the same late engagement a worn seal does. Our 6T40 family leak guide shows where these units leak and which leaks can be fixed in the car. If the complaint is late engagement, work through our delayed engagement guide first, because a solenoid or fluid problem is cheaper to fix than a teardown.

Fitment

This kit is listed for third-generation 6T30 and 6T35 transmissions, model years 2016 through 2019. It is not for the 6T40 or 6T45, which are larger units with different parts. GM made running changes across generations, so confirm the transmission RPO on your service parts label and compare the gaskets in the kit to your old ones before installation. If you are not sure which generation you have, send us the year and VIN. Older units take the 6T30 overhaul kit for 2013-2018 or the 2011-2013 kit, and every kit we carry is listed in our rebuild kits category.

Install notes

• Lay the kit out against the old parts as you disassemble so each seal goes back in the right bore.
• Soak lip seals in Dexron VI and use assembly gel on Teflon sealing rings. Size the rings before the drum goes on so they do not cut.
• Inspect every bonded piston. This kit has no pistons, and a cracked or lifted bonded piston will cause slipping no matter how good the new seals are. The 6T30 kit with pistons is listed for 2010-up units; compare its pistons to yours before choosing it.
• Check the 3-5-R wave plate for cracks at the tooth corners and replace frictions and steels if they are worn.
• Refill with Dexron VI, set the level hot at the level set plug, clear adaptive values and complete a relearn drive.

What is in this 6T30 overhaul kit?

Gaskets, lip seals, O-rings, sealing rings and the small rubber parts used inside the transmission. It does not include pistons, frictions, steels, the filter or hard parts.

Will it fit a 6T40 or 6T45?

No. It is listed only for the third-generation 6T30 and 6T35, 2016-2019. The 6T40 and 6T45 use their own kits.

How do I tell if my transmission is a Gen 3 6T30 or 6T35?

Check the transmission RPO on the service parts label in the glove box or trunk and match the model year to 2016-2019. If the label is missing, send us your VIN and we will confirm.

Should I replace pistons during the rebuild?

Inspect each one. Many 6T-family pistons have the seal bonded to the metal, so a cracked or shrunken piston must be replaced as a unit. A cracked 1-2-3-4 piston can set P2723.

What fluid does the 6T30 use and how is it checked?

Dexron VI. The level is checked hot at the level set plug in the 85-95 C (185-203 F) window after cycling through the ranges.

• 6T40 Fluid Leak: Common Spots and Fixes
• 6T40 Delayed Engagement: Causes and Fix
• 6T40 Common Problems and Fixes
• 6T40 Fluid Change Cost