Complete seven-piece shift solenoid set for the Allison 1000/2000 behind 2001-2005 6.6L Duramax trucks; fixes erratic, late, or harsh gear changes.
If your 2001-2005 Silverado or Sierra 2500HD/3500 Duramax is banging into second, flaring on the 2-3 or 3-4, sitting in third gear in limp mode, or setting a shift solenoid code such as P0751, P0752, P0973 or P0974, the solenoids bolted to the Allison valve body are near the top of the suspect list. This kit replaces the whole electrical side of the early five-speed valve body in one job, so you are not dropping the pan once for a trim solenoid and again for a shift solenoid a few months later. It cross-references OE numbers D116420A, 8683167, 29533074, 29533075 and 29536833.
The early five-speed does not use a simple pair of on/off shift solenoids like an older GM four-speed. Sonnax's identification chart for the 2001-2003 valve body lists six units: the A Trim and B Trim solenoids (about 5.5-6.5 ohms), shift solenoids C, D and E (about 22-24.5 ohms), and the F Trim or TCC solenoid (about 10.5-11.5 ohms). For 2004-2005 the same layout carries a seventh "G" solenoid at 22-24.5 ohms. The shift solenoids decide which clutch circuit is fed, while the trim solenoids control how fast that clutch applies. That split matters for diagnosis: a weak trim solenoid causes flares and harsh shifts even though the right gear is being selected, and a failed shift solenoid causes the wrong gear or a failsafe default.
Pull codes with a scan tool that reads the transmission module, not just the engine. With the pan down and the harness unplugged, measure each solenoid against the resistance ranges above; a coil reading open, shorted or well outside its range is a confirmed failure. A solenoid that measures fine cold can still drop out hot, which is why Gears Magazine's write-up on Allison flare repairs compares commanded and actual trim solenoid current cold versus hot. If every solenoid is in spec, the problem is more likely in the valve body bores, the control main relief valve, or the wiring. Our Allison 1000 valve body testing guide walks through those checks, and the limp mode causes guide covers the speed sensor and TCM faults that mimic a solenoid problem.
This set is listed for the Allison 1000 and 2000 five-speed behind the 2001-2005 6.6L Duramax LB7 and LLY in Chevrolet Silverado and GMC Sierra 2500HD and 3500 trucks, plus the 2003-2005 C4500 Kodiak. Be aware of the solenoid count split: a 2001-2003 valve body uses six solenoids, so one piece in the kit is the 2004-2005 "G" solenoid that an early truck does not have. The 2006-and-later six-speed uses a different solenoid layout with PCS1, PCS2, SS1-SS3 and a TCC solenoid, so this five-speed kit is not the right part for an LBZ, LMM or later truck. Count the solenoids on your valve body and compare connectors to the photos, or send us your year and VIN to confirm. Other versions of this kit and the matching valve bodies are in our Allison 1000 parts collection.
The solenoids are serviced from under the truck. Drain the fluid, drop the pan, pull the internal suction filter, then unplug the internal harness and unbolt the solenoids one location at a time so each new unit goes back in the same bore. Inspect the harness for heat-hardened insulation and check connector pins for spread terminals before blaming a new solenoid for an old wiring fault. Lube each new O-ring with clean fluid so it does not roll or cut on installation. Fit a new internal filter and pan gasket with a filter and pan gasket kit, change the external spin-on control main filter, and refill with an Allison-approved fluid; TES 668 fluid such as TranSynd 668 is the current recommendation and is backward-compatible with the TES 295 these trucks shipped with. Set the final level on a hot check at 160-200 F sump temperature, then clear codes and let the module relearn shift adapts over several drive cycles. Expect the first few shifts to feel firm until the adapts settle.
| Fits | Allison 1000 / 2000 5-speed, 2001-2005 6.6L Duramax LB7/LLY |
| Pieces | 7 shift solenoids |
| Replaces OE | D116420A, 8683167, 29533074, 29533075, 29536833 |
| Vehicles | Silverado/Sierra 2500HD & 3500 diesel, C4500 Kodiak |
| Ships | From the USA |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Yes, it is listed for 2001-2005. A 2001-2003 valve body uses six solenoids, so the seventh piece, the G solenoid used on 2004-2005 units, will be left over. Match connectors and count before installing.
No. 2006 and later trucks use the six-speed Allison 1000 with a different solenoid set (PCS1, PCS2, SS1-SS3 and TCC). Send your year and VIN if you are unsure which unit you have.
Unplug the internal harness and measure resistance. Trim A and B read about 5.5-6.5 ohms, shift solenoids C, D, E and G about 22-24.5 ohms, and F Trim or TCC about 10.5-11.5 ohms. Out-of-range or open readings confirm a failure.
An Allison-approved fluid. TES 668 fluids such as TranSynd 668 are Allison's current recommendation and are backward-compatible with the TES 295 fluid these trucks originally used. Set the level hot, at 160-200 F sump temperature.
Clear the codes and drive the truck through normal shifts over several drive cycles so the module can relearn shift adapts. If your scan tool supports an adapt reset, run it before the test drive.
The internal suction filter, pan gasket and spin-on control main filter, since the pan is already down. Inspect the internal harness and replace it if the insulation is cracked or the connectors are loose.
