Shop Allison 1000 Parts →
The Allison 1000 is the five- and six-speed automatic behind the 6.6L Duramax in GM's 2500 and 3500 trucks, and it also lives behind gas and medium-duty applications. It has a deserved reputation for toughness, but it is not immortal. Hard towing, deleted or tuned trucks running big power, neglected fluid, and high mileage all take their toll. The usual failure story is slipping, harsh shifts, a P0868 or C-clutch issue, or a torque converter that gives up. When a shop says the unit needs to come out, the number that follows is a big one.
For 2026, a complete Allison 1000 replacement typically runs $4,500 to $9,000 all-in. The spread is wide because an Allison built to survive a heavy tow rig costs a lot more than a bare stock reman, and labor on a heavy-duty truck is not cheap. Here is where every dollar goes.
The Real Cost Ranges
| Path | Unit Cost | Installed Total |
|---|---|---|
| GM dealer, Allison reman unit | $5,500-$7,500 | $7,000-$9,000 |
| Independent, quality reman | $3,800-$5,500 | $4,800-$7,000 |
| Built/upgraded reman (tow/performance) | $5,000-$8,000 | $6,500-$10,000 |
| Used/salvage unit, indy install | $2,000-$3,500 | $3,200-$5,000 |
The transmission is the biggest single line. On a Duramax, labor and the converter are the next two, and the converter is the part people most often try to skip and most regret skipping.
Labor: 8 to 14 Hours on a Duramax
Pulling and reinstalling an Allison 1000 on a Duramax 2500/3500 runs about 8 to 14 hours of book time depending on 4WD, crew cab length, and how much exhaust and crossmember has to come off. At 2026 heavy-duty shop rates of $130-$190 per hour, that is roughly $1,100 to $2,600 in labor. The transmission is heavy (over 300 lbs with the converter) and the truck sits high, so this is not a driveway afternoon for most people. A proper transmission jack and a lift make the difference.
The Add-Ons That Move the Number
- Torque converter. Reusing a converter from a failed Allison is a mistake. It holds debris and, on a slipping failure, is often the root cause. A new or reman converter is $400-$900; a billet triple-disc converter for a built truck runs more. Non-negotiable on any replacement.
- Transmission cooler flush. The Duramax cooler and lines are full of metal from the dead unit. Flush or replace them or the debris kills the new transmission and voids the warranty. Budget $200-$600.
- Fluid. The Allison 1000 takes a large fill, roughly 12 quarts for a service and more for a dry fill after a rebuild, of Allison TES-295-approved fluid (such as a DEXRON approved TES-295 fluid). At $10-$16 a quart this is $150-$300 of fluid. Do not let a shop use a cheaper non-approved ATF.
- TCM programming. A replacement Allison needs the TCM configured and the adaptive tables relearned. On some year ranges this is a dealer or specialist step. Budget for it or the shifts will be wrong.
- Filters, gaskets, and the spin-on filter. The Allison uses an internal filter plus, on many, a spin-on external filter. Replace both. $60-$200.
Stock Reman vs Built Unit: Which Do You Need
Stock Reman
If your truck is stock, tows within its ratings, and you are not chasing power, a quality stock reman Allison 1000 is the right call. It restores the truck to factory capability and, from a reputable builder, carries a solid warranty for a fraction of a built unit.
Built / Upgraded Unit
If the truck is tuned, deleted, running higher horsepower, or towing heavy every day, a stock reman may fail again the same way. A built Allison with upgraded clutches, a shift kit or valve body upgrade, and a stronger converter costs more up front but is the cheaper path over time for a working rig. Match the build level to how hard the truck actually works, not to how hard you wish it did.
Used / Salvage
Cheapest and riskiest. Unknown history, minimal warranty. Reasonable only on an older truck you plan to sell soon, and even then, inspect the fluid before you buy.
Rebuilding Your Allison? Get the Parts Here
If your shop is rebuilding rather than swapping a whole unit, the parts decide how long it lasts. gearboxinsider.com stocks Allison 1000 rebuild kits, clutches, valve body components, solenoids, and converters. Same-day ship before 2pm Eastern.
Shop Allison 1000 Parts →Replace or Rebuild?
The Allison 1000 is a strong candidate for rebuild rather than whole-unit replacement because the case and hard parts usually survive even when clutches and the converter do not. A competent Allison specialist can often rebuild yours for less than a reman swap while addressing the exact failure and adding towing upgrades in the same pass. Get a rebuild quote and a reman quote, then compare the warranty terms and what upgrades each includes. On these trucks the rebuild path frequently wins.
FAQ
Why is an Allison replacement more than a typical half-ton automatic?
The unit itself is heavier-duty and more expensive, the truck is harder to work on, the fluid fill is large and pricey, and the converter and cooler service add up. It is a heavy-duty job end to end.
Do I need to reprogram the TCM after replacement?
Usually yes. The transmission control module needs the new unit configured and the adaptive shift tables relearned. Confirm your shop does this.
Will a bigger cooler help my new Allison last?
Yes. Heat is the enemy on any towing transmission. A larger stacked-plate cooler with a thermostatic bypass is cheap insurance on a fresh Allison.
How long is the job?
A shop with the unit in hand typically turns it in one to two days. Sourcing a built or dealer unit can add a week.