4L85E Shift Kit 1991-09, new and ready to install. Fits the 4L85E. Ships fast from the USA.
The 4L85E went into GM's heaviest gas and diesel trucks and vans, and the owners who end up shopping for this kit usually share one story: the truck tows, the 2-3 shift gets lazy, and the direct clutch comes out black. If your Silverado or Sierra 2500/3500, Express or Savana van with the 6.0L or 8.1L shows that pattern, or a fresh rebuild is already slipping into third, this is the heavier of TransGo's two kits for the unit. The box in the photo is the TransGo 4L80E-HD2 Reprogramming Kit, sold new, with its laminated separator plate on top.
The 4L85E is GM's heavy-duty version of the 4L80E, with five-pinion reaction and output planetaries, but the hydraulics are common to both units, which is why TransGo lists one kit for both. Third gear is made by the direct clutch, and that clutch also stays on in fourth and in Reverse. TransGo calls the 3rd gear clutch the Achilles heel of the design. The HD2 plate answers it with a dual feed: a laminated triple separator plate opens a second oil path to the 3rd clutch, which TransGo says triples its torque capacity, and it does that without tearing the transmission down. The rest of the valve body, pump and internal parts in the box are calibrated for a raised line pressure curve so every apply is quick and firm.
The second job is pressure control. A worn boost valve either starves the clutches (soft 2-3, cooked direct plates) or lets pressure run away until the case, direct drum or piston breaks. HD2 swaps in a hardened, wide land boost valve and bushing and adds an EPC boost relief valve as a ceiling.
Gear ratio codes and slip do not always mean hydraulics. A failed shift solenoid or a broken internal harness will set some of the same codes, so check resistance and wiring first with our 4L85E shift solenoid symptoms guide. If the slip only shows up in third and fourth, read the 4L85E 3-4 clutch failure guide: once the direct plates are burned, the kit goes in during the rebuild, not instead of it.
This listing is cataloged 1991-09. The 4L85E itself arrived in 2002 (RPO MN8), so on a 4L85E the practical range is the 2002-2009 heavy-duty trucks and vans; the earlier years in the catalog range are 4L80E units, which this same kit also fits. TransGo lists the HD2 for 1991-2013 4L80E and 4L85E transmissions, so there is no separate 4L85E version to match. Follow the year-specific steps in the instructions, and send us your year and VIN if you are unsure which unit you have. Everything else for the transmission is in the 4L85E parts collection.
| Fits | 4L85E 1991-09 |
| Part type | Shift Kit |
| Condition | New |
| Brand | TransGo |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
This listing is the TransGo 4L80E-HD2 Reprogramming Kit, the one with the laminated triple separator plate. The regular SK kit has no separator plate and runs a smaller line pressure increase.
Yes. TransGo lists the HD2 for both the 4L80E and the 4L85E from 1991 to 2013. The two share the same valve body and hydraulic layout; the 4L85E differs mainly in its five-pinion planetaries.
No for the main work. The separator plate that dual feeds the 3rd gear clutch goes in without dismantling the unit. The return springs and intermediate snap rings in the box are only used when the transmission is apart for a rebuild.
Only when the slip is hydraulic. TransGo lists P0894 among the codes the kit addresses, but burned clutches, a bad solenoid or a harness fault can set it too, so test those first.
DEXRON VI. GM's specification sheet for its 4L85E based Supermatic unit lists DEXRON VI, and it is backward compatible with earlier Dexron fills.
