How do I know what Chevy transmission I have?

The quickest way is to read the transmission model code stamped on the case or its data tag and then confirm it against your vehicle’s VIN-based build sheet or RPO options. If you still aren’t sure, a Chevrolet dealer can verify the exact transmission from your VIN.

Identifying the transmission by physical markings

Where the code is found

Most Chevrolet transmissions carry a model code on the housing or on a small data tag. Common identifiers you may see include codes that resemble “4L60-E,” “6L80,” or “8L90.” If there is a tag, it often lists the transmission family and sometimes a date or part number. If there is no tag, you’ll find a stamped code directly on the metal of the case, usually near the bellhousing or pan area. Photograph the area to preserve the markings before they wear away.

Note the exact characters you can read and use them to determine the transmission family. If you’re unsure how to interpret the code, use official GM manuals, dealer resources, or trusted decoding guides to map the code to a specific transmission.

1. Inspect the transmission housing for a data tag or stamped model code on the side near the bellhousing or pan. Record the full code exactly as it appears.


2. If a tag is present, note any additional numbers (date, part number) that may help with cross-referencing.


3. If the code is stamped directly into the casing, locate the stamped characters and photograph them for later lookup.


4. Cross-check the observed code with GM service literature or reputable online decoders to identify the transmission family.

With the code in hand, you’ll usually be able to determine the transmission family (for example, a 4-speed-to-6-speed automatic family, or an 8-speed family) and narrow down the exact model. If markings are faded, combine this step with VIN-based verification for accuracy.

Verifying via VIN and RPO/build sheet data

Interpreting RPO codes and build sheets

Your vehicle’s VIN encodes its factory options, including the original transmission. The RPO (Regular Production Option) codes are listed on the glove box label or the door jamb and on the build sheet. These codes tell you what the factory installed when the vehicle rolled off the line. Decoding them confirms the transmission model and helps detect if a swap has occurred.

To use VIN and RPO data effectively, follow these steps.

1. Locate the vehicle’s VIN. It’s typically visible on the driver’s side dashboard near the windshield or on the driver’s door jamb.


2. Obtain the build sheet or the official RPO list for your VIN. This can be done through a Chevrolet dealer, GM’s official portals, or reputable third-party VIN lookup services that pull from GM’s databases.


3. Find the transmission-related RPO code on the build sheet or glove box label. It will indicate the transmission family or a specific option code that GM uses for that model year.


4. Cross-reference the RPO code with GM’s published RPO lists or a trusted decoder to identify the exact transmission model that was originally installed.

RPO-based verification is especially useful if the markings on the transmission are unreadable or if the vehicle has undergone a transmission swap. It provides a baseline for what the factory intended for your model and year.

Practical considerations and caveats

When to seek professional confirmation

Swaps, replacements, or dealer modifications can obscure or override the original transmission markings. If you suspect a non-original unit, or if the code is illegible, a Chevrolet dealership service department can pull your vehicle’s build data from the VIN and confirm the exact transmission model. A trained transmission technician can also inspect control modules, serial numbers, and the case markings to verify compatibility.

In some cases, the simplest path to certainty is to request the build sheet or a confirmation letter from the dealer, which references the exact transmission family installed at the factory. This is often faster and more reliable than guessing from exterior markings alone.

Summary

To determine the Chevy transmission you have, start with the physical identifiers on the transmission itself—look for a model code on the housing or data tag and note any stamping. If readings are unclear or missing, turn to the VIN-based route by obtaining the vehicle’s build sheet or RPO codes from GM resources or the dealership. The combination of case markings and VIN-derived documentation usually yields a precise identification, ensuring you source the correct parts and schedule appropriate maintenance.

How do you tell if you have a TH350 or TH400?

You can tell a TH350 from a TH400 by the pan shape, with the TH350 having a square-like pan with a corner cut off, and the TH400 having a unique, more irregular shape with one side straight. Other differences include the kickdown mechanism: TH350s use a cable, while TH400s have an electrical switch and plug on the case. The TH400 is also visually larger and heavier than the TH350.
 
You can watch this video to see a visual comparison of the TH350 and TH400 transmissions: 58sPrecision TransmissionYouTube · Jun 6, 2020
Key differences

• Pan shape:
  • TH350: Square-ish with one corner cut off. 
  • TH400: Irregular shape, with one side straight and a bulge on the other ("elephant ear"). 
• Kickdown mechanism:
  • TH350: Has a mechanical kickdown cable that runs from the carburetor or throttle linkage to the transmission. 
  • TH400: Uses an electrical kickdown with a slide switch and a plug on the side of the case, eliminating the need for a cable. 
• Size and weight:
  • TH350: More compact and lighter. 
  • TH400: Larger, heavier, and visibly more rugged. 
• Strength:
  • TH350: Designed for lighter-duty and moderate-performance applications. 
  • TH400: Built for heavy-duty and high-torque applications. 

How do I identify my Chevy transmission?

The easiest method of GM automatic transmission identification is to examine the transmission pan. New transmission designs came with new, unique pan shapes, and the general shape of the pan often paints a fairly clear picture of which automatic transmission you are dealing with.

How do I know if I have a 4L60E or 700R4?

The easiest way to identify a 700R4 vs. a 4L60E is by looking for an external TV cable on the 700R4 or a large electrical connector and a missing governor cover on the 4L60E. Other key differences include the 4L60E having a separate, removable bellhousing (on later models) and a 17-bolt pan, while the 700R4 has a one-piece case and a 16-bolt pan.
 
This video shows the key differences between the 4L60E and 700R4 transmissions: 49sMonster TransmissionYouTube · Feb 25, 2015
Primary identification methods 
This video explains the evolution of the 700R4 to 4L60E and their key differences: 1mSpeedway MotorsYouTube · May 7, 2025

Feature	700R4	4L60E
Throttle control	Has a physical TV (throttle valve) cable on the driver's side.	No TV cable; controlled electronically.
Electrical connection	No electrical case connector on the driver's side.	Has a large electrical harness connector on the driver's side, near the servo cover.
Governor	Has a governor cover on the rear tail shaft housing.	Does not have a governor cover.
Bellhousing	One-piece case with a fixed bellhousing.	Later models (1996+) have a removable bellhousing.
Oil pan	Has a square-shaped oil pan with 16 bolts.	Has a more rectangular oil pan with 17 bolts.

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How do I tell if my transmission is a 4L60E or 4L80E?

You can tell the difference between a 4L60E and 4L80E by checking the transmission pan shape, which is a reliable visual cue: the 4L60E has a rectangular pan with 16 bolts, while the 4L80E has a larger, more irregular (often described as rectangular with clipped corners) pan with 17 bolts. The 4L80E is also physically larger, heavier, and was used in heavier-duty applications like 2500/3500 series trucks and SUVs.
 
This video explains how to identify a 4L80E and 4L60E based on their physical differences: 1mPSI ConversionYouTube · Dec 8, 2020
Pan shape and bolt count

• 4L60E: Rectangular pan with 16 bolts.
• 4L80E: Irregularly shaped pan (like a rectangle with two clipped corners) with 17 bolts. 

Size and weight

• 4L60E: Lighter and smaller, weighing around 150 lbs.
• 4L80E: Significantly larger and heavier, weighing around 236 lbs. 

Vehicle application

• 4L60E: Used in light-duty applications like 1500 series trucks and SUVs. 
• 4L80E: Heavy-duty transmission used in 2500/3500 series trucks, heavy-duty Suburbans, and vans.