When a sealing ring in a TH400 or 3L80 unit wears out or cracks, internal pressure drops and the clutch circuits stop responding the way they should, and this single replacement ring is the direct answer to that problem. What separates this part from a generic option is the traceability behind it: REMCO has been sourcing and organizing automatic transmission components since 1991, and every piece that leaves the warehouse is checked against its part record before it ships.
The TH400, also cataloged as the 3L80, is a heavy-duty three-speed automatic transmission that has been in continuous use since 1965, and this ring covers that full production run from 1965 onward. If your unit falls within that range and you have confirmed the transmission code, this part is sized and spec'd to fit without modification.
This listing is for one sealing ring. There are no friction discs, no steel plates, no Automatic Transmission Filter, and no gasket set included. If your repair calls for any of those components, they would need to be sourced separately. The box ships with a printed part list inside so you can confirm at a glance that the correct piece arrived.
At 1 lb packaged, this is a small but critical part. A failed sealing ring is often the root cause of soft shifts, slipping, or pressure complaints in these units, and replacing it before a full rebuild can save diagnostic time. Confirm the transmission code on the unit and the model year before placing the order.
- This sealing ring addresses leakage and pressure loss in TH400 and 3L80 automatic transmission units, covering applications from 1965 onward with a direct-fit replacement piece.
- This listing is for a sealing ring only. It does not include any friction discs, steel plates, Automatic Transmission Filter, gaskets, or additional components. Verify your exact need before ordering to avoid a return.
- The ring is pulled from REMCO's organized inventory and checked against the part record at the time of packaging, a process the company has applied to transmission parts since 1991.
- Contents: one sealing ring for TH400 and 3L80 units. Packaged weight is 1 lb. A part list is included in the box confirming what is inside.
- Before ordering, confirm the transmission code on your unit is TH400 or 3L80 and that the application year falls within the 1965-and-later range this part covers.
What's in the box
- 1 x Ring Kit, TH400
Compatible vehicles
- Fits K2500 Panel Delivery 3/4 Ton 4WD [67].
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