Rebuilt THM425 and Related Products for the GMC TZE

Welcome to Manny’s Transmission

Manny’s Transmission provides the best, rebuilt transmission for the TZE coach as well as great service and experience. “As long as I get business from you I’ll be in business supporting the GMC community in a cost-effective manner.”

While you’re here, be sure to check out the aftermarket products we have available for the classic 1973-78 GMC motorhome.

GM’s Turbo-Hydramatic 425


The Turbo-Hydramatic 425 was an automatic transmission developed and produced by General Motors. It was a 3-speed longitudinal automatic transmission. The Turbo-Hydramatic (THM) series of transmissions were developed to replace both the original Hydra-Matic models and the Buick Dynaflow. The THM425 is a derivative of the THM400.

The THM425 was developed for the 1966 Oldsmobile Toronado and the 1967 Cadillac Eldorado. It, and the Oldsmobile 455 it was mated to, was selected for use in the motorhome wholly designed and built by GMC starting with production in 1973.

A lighter-duty transmission, known as the THM325, replaced the THM425 in GM’s vehicle lines after the 1978 model year. The THM325 became the THM325-4L with an overdrive added in 1982. All vehicles using this transmission switched to more-conventional transverse engine mounting in 1986.

The THM425 was used in the following vehicles.
  • 1966-1978 Oldsmobile Toronado
  • 1967-1978 Cadillac Eldorado
  • 1971-1979 Cortez motorhome
  • 1972-1978 Revcon motorhome
  • 1973-1978 GMC MotorHome and TransMode

Why Manny’s Transmission

Manny's Transmission is a family owned and operated business providing trusted service at a fair price to the GMC Community. Manny’s reputation is without peer when it comes to rebuilding quality transmissions for the GMC motorhome market. And, in addition to transmissions, other components and products are available to enhance your coach and your experience of ownership.

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