4L80E Master Rebuild Kit 1999, new and ready to install. Fits the 4L80E. Ships fast from the USA.
If you are rebuilding the 4L80E out of a 1999 Chevrolet or GMC 2500 or 3500 pickup, a 2500 Suburban, or an Express or Savana van, this is the master rebuild kit sized for that model year. It is new, and it is meant for the overhaul where the unit has slipped, cooked its fluid, or lost a clutch pack after years of towing, and you want every friction, steel, seal and gasket replaced in one order. 1999 is not just another year on the 4L80E timeline: it is the year GM changed the geartrain, so building a 1999 unit correctly means knowing which hard parts sit around these soft parts.
The 4L80E is GM's heavy-duty electronic four-speed, a TH400-based gearbox with an overdrive section in front. Its clutch packs and seals are what wear out first, and a master kit renews all of them so the rebuilt unit clamps and holds pressure like new. In 1999 specifically, Transmission Digest technical editor Wayne Colonna documents that the front and rear planetary carriers moved to pinions about 0.075 inch thicker (roughly 0.710 to 0.785 inch), and the sun gear was raised 0.041 inch to stay centered in the wider pinions. That makes 1999 the first year of the second-design center-lube unit, after the 1997-98 first design that moved the cooler return from the pump to the center support. The soft parts in this kit go into that 1999-and-later hard-part layout.
A full kit is the right purchase only when the clutches are actually worn. Scan for codes and test the solenoids and internal harness first, because an electrical fault can feel exactly like slipping; our 4L80E common problems and fixes guide walks through separating electrical, hydraulic and mechanical causes. Then run a line pressure test. Good pressure with slipping, or a pan full of burnt debris, points to worn clutch packs. Our 4L80E rebuild cost guide lays out what else usually gets replaced so you can budget the job before the unit comes out.
This kit is listed for the 1999 4L80E, used in that year's GM three-quarter- and one-ton trucks, Suburbans and full-size vans. Because 1999 is a production break, confirm your unit is a 1999-and-later design: pull the transmission ID tag, check the front carrier pinion width with a micrometer, and note that Colonna warns against mixing 1997-98 and 1999-up sun gear shafts and center supports. If your truck was built near the model-year changeover, send us the year and VIN before ordering. Earlier units should use the 1991-1995 master kit, and every year-specific option is on our 4L80E parts page.
Tear down and inspect every hard part before the new soft parts go in. Measure the intermediate clutch backing plate, since Sonnax's build-guide data shows the 1999-and-later plate is thinner than the earlier one, and set each clutch pack clearance to spec rather than assuming a stack count. Replace worn bushings, check the overdrive roller clutch, and swap a tired intermediate sprag for the 34-element heavy-duty sprag. A 1999 unit uses the black post-1994 pressure control solenoid, so if the solenoids are original it is a good time to fit the 1994-2003 solenoid kit while the pan is off. Soak the frictions in ATF, air-check every circuit, flush the cooler and lines, install a new converter, prime the pump, and fill with a Dexron VI fluid, which is back-serviceable for the Dexron III this transmission originally shipped with. Check the level hot after the first drive.
| Fits | 4L80E 1999 |
| Part type | Master Rebuild Kit |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is listed for 1999. The 1997-98 units are a first-design center-lube transmission with thinner planetary pinions and a different sun gear shaft, so confirm your hard parts before using a 1999 kit in an earlier unit. Send us your year and VIN if you are unsure.
Measure the front carrier pinion gears. Transmission Digest gives about 0.710 inch for the original design and 0.785 inch for 1999 and later. The center support and sun gear shaft also differ between the two center-lube designs.
Worn bushings, the torque converter, and any hard parts that fail inspection, such as the intermediate sprag or overdrive roller clutch. Many builders also add a shift kit and replace the solenoids while the unit is apart.
It originally specified Dexron III. Dexron VI is the current GM fluid and is back-serviceable for Dexron III applications, so it is the right choice for a rebuilt unit.
Not always. Check codes, the solenoids, the internal harness and line pressure first. If pressure is good and the unit still slips, or the fluid is burnt with debris in the pan, the clutches are worn and an overhaul is the fix.
