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What transmission does a 2004 Chevy 2500 have?

The transmission in a 2004 Chevrolet Silverado 2500 depends on the engine; gas-powered models use a 4-speed automatic (4L80-E), while diesel Duramax models use the 5-speed Allison 1000 automatic.

Here's how the options break down by engine, reflecting what buyers could have ordered in 2004 and how the gearboxes were matched to each powertrain.

Engine/Transmission Configurations

Gas-engine Silverado 2500

Gas-powered models used the heavy-duty four-speed automatic transmission. The examples below show common powertrains paired with the 4L80-E.

6.0L V8 (gas) paired with 4L80-E four-speed automatic

8.1L V8 (gas) paired with 4L80-E four-speed automatic

In summary, all gasoline Silverado 2500 configurations in 2004 used the 4L80-E automatic transmission.

Diesel-powered Silverado 2500HD (Duramax LB7)

The Duramax LB7 diesel in the 2004 2500HD used a different transmission.

Duramax 6.6L LB7 paired with Allison 1000 five-speed automatic

Thus diesel 2500HD models used the Allison 1000 automatic transmission.

Summary

For the 2004 Chevrolet Silverado 2500 lineup, the transmission depended on the powertrain: gasoline models used the 4L80-E four-speed automatic, while diesel-equipped 2500HD trucks with the Duramax LB7 used the Allison 1000 five-speed automatic. Always verify the exact configuration for a specific vehicle by checking the VIN or original window sticker, as there were variations across cab/bed/body styles and 4x4 vs. 2WD layouts.

How do I know if I have a 6L80 or 6L90?

The main ways to identify a 6L80 from a 6L90 are by the RPO code (6L80=MYC, 6L90=MYD), the length, and the pan shape. The 6L90 is a heavier-duty version that is approximately 1-3/8 inches longer and has a pan with a flatter corner, while the 6L80 is shorter and has a more rounded pan corner. You can also check the part numbers or look at specific internal components if you have the transmission disassembled.

This video explains the difference between 6L80 and 6L90 valve bodies: 57sBrad's TransmissionYouTube · Apr 24, 2024
Key identification methods
This video shows how to identify a transmission by using the gear selector on the dashboard: 52sCodemans autoYouTube · Nov 2, 2023

RPO Code: Look for the RPO (Regular Production Option) code on the glovebox or vehicle service tag.
- MYC: indicates a 6L80.
- MYD: indicates a 6L90.
Transmission Length: The 6L90 is longer than the 6L80.
- 6L80: Case with bell housing length is approximately 23.5 inches.
- 6L90: Case with bell housing length is approximately 25 inches (1-3/8 inches longer).
Transmission Pan: The shape of the transmission pan is a reliable indicator when the unit is out of the vehicle.
- 6L80: The pan has a rounded corner on the back.
- 6L90: The pan has a flatter corner on the back.
Part Numbers: GM part numbers for transmission parts often begin with 242. The specific part number on the TEHCM sticker (under the transmission pan) can help identify the exact model and year.

This video discusses the size differences between 6L80 and 8L90 transmissions: 1mSwap TimeYouTube · Feb 19, 2020

What year 2500hd to avoid?

Years to avoid for a 2500HD include 2003–2006 and 2014–2017 due to widespread electrical, transmission, and HVAC issues. For Ram 2500 models, the 2013 and 2018 models should be approached with caution due to engine and braking system problems respectively. More recent Ram trucks, specifically 2021-2023, have also had recalls for potential electrical and fire risks.

Chevrolet Silverado/GMC Sierra 2500HD

2003–2006: Known for a high number of owner complaints and reliability issues, especially with electrical systems, HVAC, and the engine management system.
2014–2017: Models from this period, particularly 2014, 2015, and 2017, had numerous recalls and high complaint rates.
- 2014: Had frequent air conditioning and transmission issues.
- 2015: Had a large number of recalls and is known for suspension and transmission problems.
- 2017: Is frequently cited for significant transmission problems.

Ram 2500

2013: Considered a poor year due to engine problems.
2018: Has the most complaints, with many related to the braking system.
2021–2023: Has a number of recalls and investigations regarding potential electrical shorts and fire risks.

What transmission does a 05 Lly have?

Transmission Type: Allison 1000. Power Rating: Near-Stock/Heavy Towing.

What transmission is in a Chevy 2500?

And is it actually the same Allison 10-speed transmission that's in behind the Duramax. Diesel. We'll find.

Kevin Bennett

Company Owner

Kevin Bennet is the founder and owner of Kevin's Autos, a leading automotive service provider in Australia. With a deep commitment to customer satisfaction and years of industry expertise, Kevin uses his blog to answer the most common questions posed by his customers. From maintenance tips to troubleshooting advice, Kevin's articles are designed to empower drivers with the knowledge they need to keep their vehicles running smoothly and safely.