4L80E Pump 1991-1996, remanufactured and ready to install. Fits the 4L80E. Ships fast from the USA.
A heavy-duty 1991-1996 Chevy or GMC 2500 or 3500, a Suburban 2500, or a full-size van that tows hard will eventually wear out the 4L80E front pump. The signs are hard to miss: the truck sits for a second before it takes Drive or Reverse once the fluid is hot, every gear feels soft under a load, and there is a whine that climbs with the tach even in Park. This is a remanufactured GM pump assembly for the early, pre-center-lube 4L80E, carrying GM reference 8678778 on the listing, so you can bolt in a finished pump instead of rebuilding the cover and gears yourself.
Every clutch, the band and the converter in a 4L80E run on oil the front pump makes. The converter hub drives the pump gears, and the pump cover holds the pressure regulator valve, which sets line pressure and feeds the converter, plus the boost valve, which raises line pressure when the computer commands more through the EPC solenoid and whenever Reverse is selected. On the 1991-1996 design the cooler return oil also comes back through the pump. Transmission Digest notes that GM moved the cooler return to the center support in 1997 and redesigned many hard parts around that change, which is why an early pump is its own part and not a substitute for a later one.
Check fluid level and condition first, then put a gauge on the line pressure port and compare idle and stall readings in each range to the factory chart. Low pressure everywhere points at the pump or a major internal leak; low pressure in only one range points at that circuit's seals instead. On 1994-1996 trucks with the 6.5L diesel, Transmission Digest documents that the accelerator pedal sensor commands both fueling and line pressure, so an over-fueling injection pump can make the transmission slip with a perfectly good pump. Rule out the EPC solenoid too. Our 4L80E EPC solenoid symptoms guide and 4L80E common problems guide walk through the tests.
Listed for the GM 4L80E from 1991 through 1996. It does not fit 1997 and newer center-lube units, which need the 1997-2003 4L80E pump. Early 4L80E transmissions saw running changes, and many have been swapped between trucks or rebuilt with mixed parts over the years, so compare the numbers cast into your old pump body and stator support with this one, or send us the year and VIN and we will check it before it ships. Every part we stock for this transmission is on the 4L80E parts page.
| Fits | 4L80E 1991-1996 |
| Part type | Pump |
| Condition | Remanufactured |
| Brand | GM |
| Reference | 8678778 |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. This pump is for 1991-1996 4L80E units. In 1997 GM moved the cooler return to the center support and changed many hard parts, so 1997-2003 trucks need the 1997-2003 pump.
It is a remanufactured GM pump assembly, delivered ready to install. The listing carries GM reference 8678778; compare it with the numbers on your old pump or send us your year and VIN.
Yes. The pump supplies all line pressure, so a worn pump shows up as soft or delayed engagement and slipping across every range rather than a single bad shift. Confirm with a line pressure gauge before replacing it.
A new front seal, the pump gasket and O-ring, and fresh Dexron VI at minimum. If the clutches have been slipping, a master rebuild kit and a solenoid check are worth doing while the transmission is out.
On 1994 and later 6.5L diesels the pedal position sensor sets both fueling and line pressure. Transmission Digest documents that an over-fueling injection pump can drop commanded line pressure and make the transmission slip, so check the engine side and the EPC circuit too.
