4L80E Planetary 1991-2001, new other (see details) and ready to install. Fits the 4L80E. Ships fast from the USA.
When a 1991-2001 Chevrolet or GMC 2500 or 3500, Suburban 2500, Express or Savana van or Hummer H1 loses Drive after plowing, towing or an overheat but still moves in manual 2 and 1, the front overdrive section of the 4L80E has usually failed. This update kit replaces that whole section with the later design. It contains a rebuilt updated overdrive planet, a rebuilt updated overrun drum, and new updated parts to go with them: the overdrive sprag, the overrun piston spring retainer and its snap ring. Together they retrofit any 4L80E back to 1991.
The 4L80E has a small planetary gearset at the front, ahead of the main geartrain, whose only job is to give fourth gear. In first through third the one-way clutch, or sprag, that sits inside the overrun drum locks this planetary so it turns as one piece and passes engine power straight through. In fourth the fourth clutch holds the sun gear, the sprag freewheels, and the planet steps the output into overdrive. The overrun clutch, also in that drum, only applies in manual 2 and 1, where it backs up the sprag and gives engine braking.
In Drive the sprag carries the load alone, and heat attacks it. Transmission Digest's Sonnax TASC Force article on overdrive clutch failure describes the plastic cage melting during overheat and the unit failing quickly. GM revised the overrun drum, overdrive planet and sprag late in 2000 production; this kit puts those updated parts into an earlier transmission as a matched set.
Start with a range test: drive in D, then manual 2 and 1. If only Drive is lost, the overdrive section is the main suspect. Drop the pan and look for debris before you spend money on electrical parts. Rule out a speed sensor fault too, since a bad input or output signal can set a ratio code that looks like slip; our 4L80E speed sensor symptoms guide covers that test. The 4L80E common problems guide lays out the full overdrive roller clutch failure.
For 4L80E transmissions built from 1991 through 2001, in Chevrolet and GMC 2500 and 3500 pickups, Suburban 2500, Express and Savana vans and the Hummer H1. It is a must-have for 1991 through late-2000 units with the early drum, planet and sprag, and it also fits later 2001 units. The drum and planet are professionally rebuilt cores with new updated small parts, so the exterior may show machining or wear marks. The transmission has to be removed and partly disassembled to install it. Send us your year and VIN if you are unsure of your build, and see the 4L80E collection page for other hard parts.
| Fits | 4L80E 1991-2001 |
| Part type | Planetary |
| Condition | New Other (See Details) |
| 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.
A rebuilt updated overdrive planet, a rebuilt updated overrun drum, and a new updated overdrive sprag, overrun piston spring retainer and retainer snap ring.
Yes. The kit is designed to retrofit back to 1991, replacing the early drum, planet and sprag with the updated design as a set.
In manual 2 and 1 the overrun clutch holds the overdrive planet even if the sprag has failed. In Drive the sprag works alone, so a broken one leaves you with no drive.
Yes. The overdrive section sits at the front of the case behind the pump, so the unit must come out and be partly disassembled.
Overrun and fourth clutch piston seals, any worn thrust washers or bushings, the filter, and the fluid. Clean the cooler to clear debris from the failure.
Watch the transmission temperature gauge and use manual 2 or 1 when plowing or towing slowly, so the overrun clutch backs up the sprag.
