4L85E Shift Kit 1991-2013, new and ready to install. Fits the 4L85E. Ships fast from the USA.
Hauling a heavy trailer or a camper with a 4L85E and feeling the 2-3 shift stretch out, or tearing down a van transmission to find the direct clutch burned again, is exactly what this kit is for. It is a new TransGo 4L80E-HD2 Performance Reprogramming Kit, sold to shops under the T34169E number, and TransGo lists it for 1991 through 2013 GM vehicles with the 4L80E or 4L85E. That covers 6.0L and 8.1L Express and Savana vans, Chevrolet and GMC 2500 and 3500 trucks, Suburban and Yukon XL 2500s, and plenty of swap builds.
The 4L85E got stronger five-pinion gearsets, but its hydraulics are the same as the 4L80E's, and so is its weak point. The direct clutch applies in third, stays on in fourth and also works in Reverse, and TransGo calls this third gear clutch the Achilles heel of the design. The HD2 kit's laminated triple separator plate dual feeds that clutch, which TransGo says triples its torque capacity, and you do not have to take the transmission apart to get it.
The second fix is pressure control. The factory boost valve and bushing wear until pressure either sags, giving a soft 2-3 shift, or runs away, which can break the case, the direct drum and the piston. HD2 swaps in a hardened, wide land, USA-made boost valve and bushing, adds an EPC boost relief valve as a safety limit, and recalibrates the valve body, pump and accumulators for a higher line pressure curve.
The kit corrects hydraulic weak spots. It will not fix an open solenoid, a chafed harness or a failed speed sensor, and codes like P0751 and P0756 point there first. Test the circuits as shown in our 4L85E shift solenoid guide, then check line pressure and the valve body using the 4L85E valve body testing guide. If the 2-3 shift already slips and the fluid smells burnt, the direct clutch is damaged; read our 4L85E clutch failure guide and plan to install this kit during the rebuild rather than on top of worn frictions.
TransGo lists this kit for every 1991 through 2013 4L80E and 4L85E, so it is one of the few parts that spans early four-pinion units and late 4L85E vans alike. The valve body layout is shared across the family. Early 1991-1996 cases are hydraulically different in places, so read the instruction sheet for the steps that apply to your year before drilling anything. If you want us to double-check, send your year, vehicle and VIN. See every part for this unit on our 4L85E parts page.
| Fits | 4L85E 1991-2013 |
| 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.
It is the TransGo 4L80E-HD2 Performance Reprogramming Kit, distributor number T34169E. TransGo makes one HD2 kit that covers both the 4L80E and 4L85E.
The triple separator plate's direct clutch dual feed works without a teardown. Some of the kit's parts, like the direct clutch return springs and case snap rings, are installed when the unit is apart, so the full kit is best done during a rebuild.
It raises line pressure and firms the shifts to cut clutch slip time. Most heavy-duty owners find it firmer but not harsh. The kit is aimed at durability under load.
Only if the cause is hydraulic. P0756 and P0751 can also come from a failed solenoid or wiring. Test the solenoid circuit first.
Frictions and steels if the direct clutch is burnt, the filter, and a worn pressure control solenoid. Use Dexron VI fluid.
