This is an Allison 1000 transmission for sale in fairly used condition: a heavy-duty automatic out of a GM heavy-duty pickup or medium-duty truck, inspected and ready to ship anywhere in the world. It is the gearbox behind the Duramax diesel in the Chevrolet Silverado and GMC Sierra 2500HD and 3500HD, and it is known for taking serious towing loads without complaint.
Send us your VIN and we will match the Allison 1000 transmission for sale to your truck before you pay. Five-speed or six-speed, two-wheel drive or four-wheel drive, diesel or petrol bellhousing: these details decide whether it bolts straight in.
Table of Contents
What Comes With This Allison 1000 Transmission for Sale
- Complete transmission with the gear sets and clutch packs
- Torque converter (condition noted on your quote)
- Valve body and internal solenoids
- Bellhousing and tail housing to suit the version
- Packing on a pallet with the openings sealed for shipping
The transfer case, TCM, cooler lines and shifter are not included unless agreed in writing. If you need any of those, ask what we have.
Allison 1000 Transmission for Sale: Specifications
| Transmission | Allison 1000 Series (GM also calls it the LCT1000) |
| Type | Electronically controlled automatic, rear-wheel-drive layout |
| Speeds | 5-speed (early) or 6-speed (from about 2006) |
| Gear ratios, 6-speed | 3.10, 1.81, 1.41, 1.00, 0.71, 0.61, reverse 4.49 |
| Gear ratios, 5-speed | 3.10, 1.81, 1.41, 1.00, 0.71, reverse 4.49 |
| Converter | Lock-up torque converter |
| PTO | PTO provision on many versions |
| Typical engines | Duramax 6.6 V8 diesel, Vortec 8.1 V8 petrol |
| Years in GM HD pickups | 2001 to 2019 |
The two overdrive gears on the six-speed are a big part of why later trucks are quieter and use less fuel on the highway. You can read more about the Allison 1000 and its history if you are interested in the details.
Which Trucks Use the Allison 1000?
- Chevrolet Silverado 2500HD and 3500HD with the Duramax diesel (LB7, LLY, LBZ, LMM, LML and early L5P)
- GMC Sierra 2500HD and 3500HD with the Duramax diesel
- Silverado and Sierra HD trucks with the Vortec 8.1 petrol V8
- Chevrolet Kodiak and GMC TopKick medium-duty trucks
- A range of other medium-duty trucks, buses and motorhomes
From the 2020 model year, GM moved the Duramax trucks to a ten-speed. If your truck is a 2019 or earlier HD with the Duramax, the Allison 1000 transmission for sale on this page is very likely the right one. The Duramax V8 generations are worth knowing, because the transmission was updated alongside them.
Five-Speed or Six-Speed?
Early trucks, roughly up to the 2005 or 2006 model year, have the five-speed. Later trucks have the six-speed. The case looks similar, but the internals, the software and the wiring differ. A six-speed can go into an earlier truck, but it needs the right TCM and wiring work. For a straight replacement, match what your truck came with.
Other Details That Must Match
- Two-wheel drive or four-wheel drive. The tail housing and output shaft are different.
- Diesel or petrol. The bellhousing and converter differ between the Duramax and the 8.1 petrol V8.
- PTO. If your truck runs a PTO, make sure the replacement has the provision.
- TCM software. The transmission control module needs to suit the transmission and engine.
The VIN answers most of these questions. That is why we ask for it before we sell any Allison 1000 transmission for sale.
Why the Allison 1000 Has a Strong Reputation
It was built for work. Heavy clutch packs, a strong case and a lock-up torque converter let it handle the torque of a diesel V8 pulling a big trailer. Owners of Silverado and Sierra HD trucks often say the Allison is the reason they bought GM. Looked after with clean fluid and a healthy cooler, these transmissions last a very long time.
Common Allison 1000 Problems
- Overheating from towing. Heat kills automatic transmissions. Check the cooler and lines.
- Old or wrong fluid. Use the correct approved fluid and change it on schedule, more often if you tow.
- Converter wear in tuned trucks. Big power tunes on the Duramax push the converter and clutches hard.
- Shift solenoids and wiring. Electrical faults can look like mechanical ones. Scan for codes first.
These are the things we look at on every Allison 1000 transmission for sale we ship.
How We Check Each Allison 1000 Transmission for Sale
Every unit goes through our inspection before it ships. We look at the fluid for colour, smell and debris, check the case and housings for cracks and damage, check the input and output shafts, and look for leaks. We tell you what we know about the truck it came from and the mileage, and where that figure came from. If you want to know what different checks can tell you, our guide to tested used engines explains the idea, and most of it applies to transmissions too.
Signs Your Current Allison Is on the Way Out
Not every problem means a new transmission. But if you are seeing several of these together, it is probably time to price up an Allison 1000 transmission for sale:
- Slipping, especially in higher gears or under load
- Harsh or delayed shifts that do not go away after a fluid change
- Dark, burnt-smelling fluid with metal in the pan
- The truck going into limp mode and holding one gear
- Shuddering when the converter locks up
Before you buy anything, have the codes read and the fluid checked. Sometimes a solenoid, a wiring fault or a sensor is the real problem, and that is a much cheaper fix.
What to Ask Before You Buy Any Allison 1000
- Is it a five-speed or six-speed?
- Two-wheel drive or four-wheel drive?
- Did it come from a diesel or petrol truck?
- What year and model was the donor truck, and what was the mileage?
- Does it have the PTO provision?
- Is the torque converter included, and what condition is it in?
We answer every one of these for each Allison 1000 transmission for sale we offer. If another seller cannot, think twice. These transmissions are strong, but only if you get the right one for your truck.
A tip from experience: if your truck tows heavy, think about fitting a larger transmission cooler at the same time as the replacement Allison 1000 transmission for sale goes in. It is a small cost and it is the single best thing you can do for transmission life.
Installation Tips
- Confirm five or six speed, 2WD or 4WD, and diesel or petrol before ordering.
- Flush or replace the transmission cooler. Debris from a failed transmission can ruin the new one.
- Fill with the correct fluid to the right level, checked hot and running.
- Make sure the converter is fully seated before bolting the transmission to the engine.
- Check the TCM is set up correctly, and let it relearn shift points.
- Scan for codes and check for leaks after the first drive.
Price of This Allison 1000 Transmission for Sale
The price of this Allison 1000 transmission for sale is at the top of the page. That is for the transmission itself. Shipping is covered in our shipping policy, and import charges depend on your country. Fitting is extra and depends on your mechanic.
Warranty, Shipping and Ordering
Ask us about warranty cover for this transmission before you order and we will set it out in writing. Our terms and services and refund and returns pages explain how claims and returns work.
We ship worldwide. The transmission is drained, sealed and strapped to a pallet, and you get tracking. To order, send us your VIN through our contact page or add it to your cart. You pay by bank transfer and get an invoice. If you have not bought heavy parts online before, our guide on how to buy used engine online covers the same questions you should ask about a transmission.
Related Parts We Sell
If the engine needs replacing too, have a look at our Duramax LML engine for sale and read our Duramax LML buying guide. We also sell the 6.7 Cummins and the 6.7 Powerstroke, plus transmissions such as the Toyota Land Cruiser automatic transmission. Browse the shop for everything we have.
Allison 1000 Transmission for Sale: Questions
Will this fit my 2008 Silverado 2500HD Duramax?
A 2008 Duramax HD has the six-speed Allison 1000. Send the VIN and we will confirm 2WD or 4WD and the details.
Is the converter included?
Normally yes. We note its condition on your quote.
Can it handle a tuned Duramax?
A stock Allison handles mild tunes. Big power needs upgraded clutches and a stronger converter.
Do you ship worldwide?
Yes. Tell us your country and we will explain delivery and timing.
If your truck needs a strong, proven Allison 1000 transmission for sale, send us your VIN today and we will get back to you with the details.
Want the full background before you buy? Read our Allison 1000 buying guide for specs, common problems, fitting tips and costs.
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