4L85E Overhaul Kit 1997-04, new and ready to install. Fits the 4L85E. Ships fast from the USA.
When a heavy-duty GM truck or van with the 4L85E starts slipping on the 2-3 shift under a load, loses fourth on the highway, or comes back from a tow with a dark, scorched dipstick, the transmission is usually past the point where a fluid change helps. This overhaul kit is for building a 1997 through 2004 4L85E back up on the bench. Those years matter: 1997 is when GM moved the 4L80E family to center-gearbox lubrication, so parts for these units are sorted differently from the earlier 1991-1996 cases.
The 4L85E is the heavy-duty version of the 4L80E (GM RPO MN8 versus MT1 for the 4L80E). It is a TH400-based gearbox with an overdrive section in front, and it holds its gears with the overrun, forward, direct and fourth clutches, a front band, a rear band and two one-way clutches. Every clutch is applied by fluid that has to get past rubber piston seals and the sealing rings on the shafts and drums. Heat and towing harden those seals and glaze the frictions, so apply pressure bleeds off and the pack slips, which makes more heat. An overhaul kit replaces that whole wear layer in one order. The product photo shows friction plates, steel plates, a band, a filter, bushings, and the full seal and gasket set; compare the photo to the parts you plan to replace before you order.
A new kit only fixes what is worn inside the case, so check the cheaper causes first. Scan for codes and rule out a failing pressure control solenoid or shift solenoid, since an electrical fault can look like a slip. Check line pressure: Sonnax documents a worn boost valve sleeve that lets line pressure climb out of control, causing buzzing, harsh Reverse and broken direct drums. If that sleeve is not fixed, a fresh rebuild can be damaged quickly. Then drop the pan; clutch lining and a burnt smell mean the unit is coming apart anyway. Our 4L85E common problems guide shows the order to test in, and the 4L85E 3-4 clutch failure guide covers the most common burnt pack.
This kit is listed for the 1997 through 2004 4L85E, and the same kit also serves the matching 4L80E years, because the two units share their seals, gaskets and most clutch parts. Inside that window there are hard-part changes to keep in mind. Transmission Digest notes the 1997 center-lube redesign and a move to thicker planetary pinions in 1999. Soft parts cross those years more freely than hard parts do, but some 2004 units are grouped with the later design, so confirm a 2004 carefully. Match the ID tag on the case, or send us your year and VIN and we will check it. See our 4L80E vs 4L85E guide for how the two units compare, and the 4L85E parts page for other years.
| Fits | 4L85E 1997-04 |
| Part type | Overhaul Kit |
| Condition | New |
| Brand | GM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
The 4L80E and 4L85E of the same years share their seals, gaskets and most clutch parts, and this kit is offered for both. Check your ID tag or send us your year and VIN to confirm.
The product photo shows frictions, steels, a band, a filter, bushings, seals and gaskets. Compare the photo with your old parts before ordering.
No. This kit is listed for 1997-2004. The 1997 change to center lubrication altered several parts, so a 1991-1996 unit needs a kit for those years.
Inspect the pump, bushings and drums. Check the valve body for a worn boost valve sleeve and 3rd and Reverse checkball sleeve, and flush the cooler. Many builders also replace the pressure control solenoid.
GM lists Dexron VI for service on this family. Soak the frictions in it before assembly and check the level with the fluid hot.
