4L60E Master Rebuild Kit Less Steels, 2004-Up

Part number W74004EC is a master rebuild kit for 2004 and later GM 4L60E transmissions in Silverado and Sierra 1500, Tahoe, Yukon, Suburban and the other late rear-wheel-drive GM trucks. It is the budget path for a full rebuild: a complete friction clutch module plus every gasket and seal, but no steel plates. If your late 4L60E is slipping in fourth, flaring on the 2-3 shift, or has burned up the 3-4 pack, and your steels come out of the teardown flat and clean, this kit gets the unit relined and resealed without paying for steels you do not need.

What this kit does in a 2004-up 4L60E

The 4L60E holds each gear by squeezing frictions against steels in the forward, overrun, 3-4, reverse input and low-reverse packs, with the 2-4 band handling second and fourth. The frictions are the wear item; the steels are the hard reaction surface. W74004EC replaces the frictions as a module and pairs them with the overhaul gasket set, O-rings, Teflon and metal sealing rings, lip seals and bonded rubber components, so every piston and every circuit is resealed while the unit is apart. It also carries the wedge-type front pump seal used on the later case and pump.

Symptoms this kit addresses

• Slip or loss of fourth gear under throttle, the common burnt 3-4 pack failure
• 2-3 flare or a soft, slow third gear apply
• Slipping in several gears with dark fluid and lining in the pan
• Fluid leaking at the front of the case from the pump seal, or from the pan and tail seal
• Delayed reverse from leaking piston seals

How to confirm before you buy

Make sure the slip is mechanical. Torque converter clutch slip codes are often caused by valve body bore wear, and Sonnax ties TCC regulator bore wear to slip codes and overheated converters, which can feel like clutch slip on the highway. A Sonnax-style vacuum test of the valve body separates those problems. Start with our 4L60E common problems guide, and if you are not sure whether your overrun pack is involved, read the overrun clutch guide.

Can you reuse your steels?

This kit assumes you can. A reusable steel is flat when laid on a surface plate, has no blue or purple heat discoloration, no hot spots, and no grooves you can catch with a fingernail. Steels from a pack that burned badly are usually warped or glazed and should be replaced; any that fail inspection can be bought separately. Mixing new frictions with heat-damaged steels is a common reason a fresh rebuild slips again.

Fitment

The listing covers GM 4L60E units from 2004 on. The pump seal in this kit is the wedge type used on later units; earlier pumps use a different seal, so pull your old pump seal and compare it before reassembly, and match the valve body gasket to the one you remove. If your truck is a 2004-2005 changeover year or you are unsure, send us the year and VIN. Other kits, including earlier years and full-steel versions, are in the 4L60E collection.

Install notes

• Soak the new frictions in clean Dexron VI before building the packs, and fill the unit with Dexron VI.
• Install new sealing rings on the input shaft and stator, and set clutch clearance as you stack each pack.
• Seat the wedge seal fully in the case before lowering the pump. A front pump puller with adjustable clamp jaws pulls the pump straight without damaging the pump.
• Inspect the input drum for cracked or worn lugs and a scored bore; the 4L60E input drum is the common replacement.
• Set end play in the 0.005-0.036 in range, aiming near the middle.

Add a new filter and have the converter serviced before the truck goes back on the road. Ships from the USA.

Does the W74004EC kit include steel plates?

No. It is a less-steels kit. You reuse your steels if they are flat and not heat-blued, or buy steels separately.

Which pump seal comes in this kit?

The wedge-type front pump seal used on later 4L60E units. Compare it to the seal you remove, because earlier pumps use a different design.

Will it fit a 2003 4L60E?

The listing is for 2004 and later units. For a 2003 or a changeover-year truck, check the pump seal type or send us the year and VIN before ordering.

What else should I buy with it?

A new filter, any steels that fail inspection, bushings and drums that are worn, and a converter service. A shift kit is a common addition when the 3-4 pack burned.

What fluid should I use?

Dexron VI for soaking the frictions and filling the transmission. Check the level hot, engine running, in park.

• 4L60E Common Problems, Symptoms, and What to Actually Do About Them
• 4L60E Overrun Clutch: Function, Wear and Symptoms
• 4L60E Rebuild: The Bench Tools You Actually Need
• 4L60E 1-2 Accumulator and Shift Feel: Diagnosis