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The Allison 1000 (factory designation LCT1000) is the transmission bolted behind every GM 6.6L Duramax since 2001, and it shows up in medium-duty trucks and motorhomes as well. It is one of the toughest automatics ever put in a pickup, but it is not immortal. Burned C2 clutches, a worn torque converter, and tired seals will eventually put one on the bench, and when that happens you need the right rebuild kit the first time.
The mistake people make is buying by price. An Allison 1000 has multiple generations and two transmission families — the early 5-speed and the later 6-speed — with different clutch and steel counts. Order the wrong kit and you will be standing at the bench with a drum that needs five frictions and a bag that holds four.
Identify Your Allison First
Before you buy anything, confirm which Allison you have. The two big dividing lines are speed count and generation.
- 5-speed (2001-2005, A50 / 1000): earlier valve body, fewer clutches in some packs.
- 6-speed (2006 and up, A40/A50 6-speed): revised packs, added clutch capacity, different friction counts.
- Generation matters too. GM revised the Allison several times for clutch capacity. The C2 clutch pack count in particular changed, which is exactly why a "universal" kit can leave you short.
The safe move: pull your transmission service tag / RPO and match the kit to the exact year and speed count, or buy from a seller who lists the kit by year range and clutch count so there is no guessing. See our transmission identifier guide if you are not sure what you have.
What a Complete LCT1000 Rebuild Kit Should Include
"Rebuild kit" means different things to different sellers. Match the kit to the depth of your build. There are three tiers.
| Kit Tier | What It Includes | Typical Price Range |
|---|---|---|
| Banner / overhaul kit | Gaskets, all seals, sealing rings, metal-clad seals, filters. No clutches. | ~$120 - $260 |
| Master kit (with frictions) | Everything in the banner kit PLUS the full friction clutch set for every pack. | ~$350 - $650 |
| Master + steels + bushings | Master kit PLUS new steel plates and bushing set for a complete clutch-to-clutch rebuild. | ~$550 - $900+ |
For a transmission coming apart because clutches burned, do not buy the banner kit. You need a master kit (frictions included), and on a high-mileage or built unit you want new steels too — reusing glazed, heat-blued steels with fresh frictions is a false economy that puts you right back on the bench.
Browse Allison 1000 rebuild kits
What Else You Will Need (Not Always in the Kit)
Even a "master" kit usually leaves out the big-ticket and wear items. Plan for these separately:
- Torque converter. If yours is worn or you are adding power, a fresh or upgraded triple-disc converter is the heart of the job. Do not reuse a tired converter behind a fresh rebuild.
- C2 / clutch capacity upgrade. Built Duramax units often add a clutch to the C2 pack for towing or power. If that is your goal, buy a kit built for it, not a stock count.
- Bushings and bearings if not in your tier.
- A new or rebuilt valve body or separator plate if shift quality was a problem.
- Allison TES 295 / TES 668 spec fluid for the refill. The Allison takes a lot of it. See our TES 295 vs TES 668 guide.
Check Allison 1000 torque converters
How to Avoid Buying the Wrong Kit
- Confirm 5-speed vs 6-speed. This is the first filter on every listing.
- Match the year range exactly. "2001-2010" listings are fine only if the seller accounts for the generation differences.
- Check the friction count. A real master kit lists how many frictions are in each pack. If the listing will not tell you, it is a guess.
- Buy frictions and steels from a known brand (the same names you see in every shop) rather than a no-name bag. The clutch material is the whole point of the rebuild.
- Talk to a human if you are unsure. A parts seller who knows the Allison will save you a second teardown.
Allison 1000 Kits, Frictions & Converters — Ships Same-Day
Skip the guesswork. gearboxinsider.com carries Allison 1000 / LCT1000 master rebuild kits, friction sets, steels, and torque converters matched to your year and speed count, and ships same-day before 2pm Eastern with free shipping on every order. Get the right kit the first time and keep your build moving.
Shop Gearbox Insider →FAQ
Is an Allison 1000 worth rebuilding?
Almost always yes. A properly rebuilt Allison behind a Duramax is good for another 200,000-plus miles, and a quality rebuild with upgraded clutches costs a fraction of a replacement unit. This is one of the best transmissions to put money into. See our rebuild-vs-replace breakdown.
Do I need the converter, or can I reuse mine?
If the unit was slipping, ran hot, or had clutch material in the fluid, replace or rebuild the converter. The debris from a failed clutch pack ends up in the converter, and you cannot fully flush it out. A new converter behind a rebuild is cheap insurance.
How much fluid does an Allison 1000 take?
A lot — a full deep-pan refill can run well into the double digits in quarts of TES-spec fluid. Buy by the case and confirm your pan depth. Use only Allison-approved TES 295 or TES 668 fluid.