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How To Rebuild and Modify GM Turbo 400 Transmissions: Hydra-Matic Automatic Trans

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Since its introduction in 1964, the GM Turbo Hydra-Matic 400 transmission has been used in — literally — millions of cars, trucks and more.

The Turbo 400 was the automatic tranny of choice for its durability and simplicity, not to mention versatility since it could handle whatever you threw at it; family car, hot rod, race car, dragster, off-road truck or any vehicle needing a durable and reliable automatic transmission.

And since the Turbo 400 does not rely on computer controls, it was adapted to a wide range of configurations.

Rebuilding the Turbo Hydra-Matic 400 transmission is not particularly difficult, but it requires care and attention to detail, and this is where How To Rebuild & Modify GM Turbo 400 Transmissions comes in.

The manual, packed with hundreds of sharp, close-up color photos, shows you how to remove the tranny from a typical vehicle, a complete teardown, inspection and step-by-step reassembly of the unit.

And for those who plan to use their Turbo 400 for high-performance applications, tips and advice on the subject are also included. Plus factory and aftermarket upgrades, parts interchange advice, and a transmission identification guide.

This book is a must-have for the GM Turbo 400 transmission do-it-yourself mechanic or enthusiast.

Book Excerpt: How To Rebuild and Modify GM Turbo 400 Transmissions


Automatic transmissions have always fascinated me. I can still remember the very first unit that I took apart more than 30 years ago.

It was a General Motors TH400 from an early 1970s Pontiac Bonneville. It seemed like the task of removing parts from the case would never end.

Even the valve body, which on TH400 is quite simple compared to most other models, contained dozens of parts.

I was afraid that a part or two was going to be left over after the rebuild was complete.

I laid each part out very carefully in a long line across the workbench, while paying very careful attention to which direction it had been in.

I noted if any thrust washers, snap rings, or other parts were above it, below it, or held the part in the case or inside of another part within the case.

During the rebuild, I gave every part special attention, not only to make sure that I didn't get it upside down or out of place, but also to make sure it was in good serviceable condition and could be reused without causing a malfunction.

My close attention to detail paid off. After many hours of cleaning and then installing new seals, gaskets, sealing rings, and clutch plates, I reinstalled the reassembled unit and it worked flawlessly in all areas.

Although I have built hundreds of these units since my very first experience, I use the same attention to detail and it has always served me well.

One major component in transmission units is a torque converter, which drives an oil pump located in the front housing bolted to the case.

The torque converter is bolted directly to the engine's crankshaft, and transfers all of the energy to the rear wheels.

It routes these forces through the transmission's internal components, allows for enough slippage so the vehicle can remain at a stop at idle speed, and is efficient enough to provide very close to complete energy transfer at various vehicle speeds.

Torque converters equipped with an internal clutch can actually be employed once the vehicle is in motion, to provide a complete or solid lock between the engine's crankshaft and the transmission's input shaft, just like the clutch does in a manual transmission.

  • Tools and Equipment
  • Transmission Fundamentals
  • Transmission Removal
  • TH400 Disassembly
  • TH400 Assembly
  • TH400 Transbrake
  • Transmission Installation
  • Troubleshooting Guide
  • Source Guide
ABOUT THE AUTHOR: Cliff Ruggles has more than 20 years' experience in custom building Turbo 400 transmissions. He owns and operates Cliff's High Performance, which specializes in building high-performance engines, transmissions and carburetors.

Subject: How to rebuild GM Turbo HydraMatic automatic transmissions. ISBN-10: 1934709204 | ISBN-13: 9781934709207 | CarTech SA186

  • Publisher: CarTech Books
  • Author: Cliff Ruggles
  • Pages: 144 - Hundreds of color photos
  • Binding: Paperback - 8.5 x 11 inches
  • ISBN: 978-1-934709-20-7