4L85E Overhaul Kit 1991, new and ready to install. Fits the 4L85E. Ships fast from the USA.
1991 was the first year GM built the 4L80E. It was the electronically shifted, overdrive successor to the TH400 in heavy-duty pickups, Suburbans and vans. The family was later sold as the 4L85E too, which is why this kit is listed under that name. If your early unit drips from the pan and pump, goes into gear late, or has lost Reverse, start with this overhaul kit. The photo shows a boxed gasket and seal kit. That is the reseal side of a rebuild, priced for someone who already knows the clutch packs are still serviceable or who is buying frictions separately.
The 1991 design is the original one. It has TH400-style gearing behind an overdrive section, and its cooler return comes back through the pump instead of the center support. Each of its clutches and bands is applied by fluid that the seals have to hold. Those include the piston lip seals, the sealing rings on the input and output shafts and the drums, and the gaskets between the pump, case, valve body and pan. On a 30-plus-year-old case those parts are the first to go. They harden, shrink and let pressure escape, so a unit with good plates can still slip and engage slowly. This kit puts a new sealing layer back in it.
Drop the pan before you order. Clean fluid with little lining material means seals are the likely problem and this kit fits the job. Heavy friction debris means you need plates as well. For a no-Reverse complaint, Sonnax recommends splitting the circuits: check whether the direct clutch or the low/reverse band is losing apply oil before you condemn the whole unit. Also rule out the electrical side on a truck this age. Our shift solenoid guide and the common problems guide walk through those checks.
This kit is listed for 1991 only. That is the early, non-center-lube design. Soft parts are close to those in the 1992-1996 units. From 1997 the lubrication path and several hard parts changed, and Transmission Digest warns that a non-center-lube sun gear shaft in a center-lube unit restricts the cooler circuit. The result is converter clutch drag that can stall the engine in Overdrive or Reverse. The same caution applies in reverse: keep 1991 hard parts in a 1991 case. Match the tag on the case, or send your year and VIN and we will confirm. Other early-year parts are on our 4L85E collection page.
| Fits | 4L85E 1991 |
| Part type | Overhaul 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.
No. 1991 was the first year of the 4L80E, and the 4L85E name came later for the heavy-duty version. Both share the same basic seal layout. This kit is listed for 1991 units in that family.
The photo shows a boxed gasket and seal overhaul kit, with no frictions or steels. If your plates are burnt, add a master rebuild kit or buy frictions and steels separately.
It is listed for 1991. In 1997 the unit moved to center-support lubrication and some parts in the lube path changed. For later units, pick the kit listed for your year or send us your VIN.
It can, if the direct clutch or low/reverse servo seals are leaking. Air-check both circuits first. A burnt direct clutch or a worn band needs more than seals.
Use Dexron VI. GM's current spec replaces the earlier Dexron grades. Check the level hot, in Park, with the engine running.
