The 4L60-series of transmissions (usually called the 4L60-E) are a group of automatic transmissions designed for specific General Motors vehicles. The 4-speed transmissions use a hydramatic operation and began production in 1992. They are meant for longitudinal engine configurations.
While all of that sounds complicated, it's not nearly as complex as it seems. The old THM700 was renamed a 4L60 and began being used under that name in vehicles in 1993. It's meant for rear-wheel drive vehicles like small trucks, SUVs, some sedans, etc.
In 1994, the 4L60 was upgraded to the 4L60-E, which is more or less the same transmission as before, but is now electrically shifted rather than pneumatically shifted (hence the "E"). This gives more control to the engine computer and allows for greater efficiency.
Older transmissions were shifted based on the engine's compression ratio. The higher the compression, the faster the engine is likely moving, the more likely it's time to shift gears. These newer systems allow the engine's computer to monitor performance and shift the transmission based on electrical signals when it's most prudent to do so.
Which Models Have the 4L60-E?
Several popular rear-wheel drive models have it. This includes the Buick Rainier and Roadmaster; the Cadillac Escalade, Brougham, and Fleetwood; the Chevrolet Astro, Avalanche, Blazer, Camaro (to 2002), Caprice, Colorado, Corvette (to 2004), Express, Impala SS, S-10, Silverado, SSR, Suburban, Tahoe, and TrailBlazer. Most other rebranded models under GMC, Pontiac and Holden are also using the 4L60-E.
The 4L60-E is being phased out in favor of the newer 4L65-E beginning in 2003, which has better performance.