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How to Rebuild and Modify Your Manual Transmission

Book Review

by Ryan King

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Here's the scenario: I need to rebuild the T5 five-speed manual transmission in my '93 Mustang. I've rebuilt one before, for my first '87 Mustang, and was successful (and by successful, I mean it worked for quite a few years), but not exactly due to knowing what I was doing. I diligently followed the instructions in the factory Ford repair manual which showed me how to disassemble and assemble the components, but not how to check for worn gears, synchros, and other defects in the rest of the "large" parts (such as shafts and the case as opposed to "small" parts that are made up of the blocker rings, bearings, etc).

I wanted a book that would get me started, explain the basics, and show me the ins and outs of transmission rebuilding, but I didn't have the time to read a full-blown professional text on the subject.

Enter How to Rebuild and Modify Your Manual Transmission. It fit my needs perfectly: enthusiast-focused information that touches on basic engineering and theory, and shows in detail, how to inspect, rebuild, and even blueprint and modify a manual transmission or transaxle. Author Robert Bowen does a great job conveying the information on what could be a very boring and tedious subject in an interesting and easy to read manner. While it isn't a professional text for training or a manual on engineering, I think it does a fantastic job of bridging the gap between the two — as the author set out to do — and does so concisely enough to keep it from getting hard to read.

Let's take a look at what this book has to offer.

The Book

Chapter 1: Transmissions: the Basic Concepts

Chapter 1 is a great introduction to what a manual transmission is and how its parts work together to transfer power from the engine to the drive wheels, as well as its roll in meeting the needs of various types of vehicles in situations such as street, road, and drag racing. As the author points out, the subject matter is basic if you already understand transmissions and physics, however, I did learn a thing or two and I've always found it a good idea to review the basics, especially from someone else's perspective, because — as was the case here — they may know or see something in a different light than I had previously learned or thought. The only criticism I have would be that the book states the rotation of the output shaft incorrectly. The purpose of the reverse idler gear is to change the rotation of the output shaft to be opposite of the input shaft, not to make it the same direction.

Chapter 2: The Internal Parts of a Manual Transmission

In this chapter, the author takes a close look at the individual parts that make up a manual transmission. He also explains how these parts wear as the transmission ages and what will happen with poor maintenance. I learned quite a bit from Chapter 2 — more than I expected to — and found myself really getting into the book. I found the information on API oil grades and the way they effect different types of transmission/synchro construction especially interesting.

Chapter 3: Problems and Diagnoses

I found this chapter very helpful for figuring out what to look for in the '93 LX's transmission so that I can fix some specific issues I have with age and use related wear characteristics that drive me nuts, such as notchy shifting and whining gears. Robert Bowen goes through virtually every component as well as the kinds of sounds and driving problems that indicate an issue, either internally or outside the transmission. He also explains what steps to take to diagnose them and what to repair or replace to fix the problem. Another helpful part of this chapter is a look at what "problems" you can reasonably expect to remedy and which are just natural characteristics of manual transmissions and may not have a solution.

Chapter 4: Rebuilding a Transmission

This — along with the information in the previous chapter — was exactly what I was looking for when I set about to find a book on manual transmissions: insight into the wear characteristics of the transmission components, what needs to be replaced when rebuilding a transmission, and how to assemble them correctly. For me, this chapter is worth the cost of the book. I feel I can confidently inspect the components inside the transmission of my '93 Mustang and replace those I think will either cause me immediate problem, or won't provide the full service life of a new transmission.

Chapter 5: The Tremec/BorgWarner T5

Okay, for me, this chapter is a no brainer. Obviously it was helpful for me, and as the author mentions, the reason this trans was chosen was both the T5's popularity and it's similarity to just about every other rear wheel drive manual transmission ever built. Now, I have rebuilt a T5 before and have some experience with the process, and the book does a good job going through the rebuilding process, although I would have liked to have seen some mention of the rubber "ring" on the mainshaft as I have yet to find literature that describes it and its function.

Chapter 6: The Honda B-Series Transaxle

I had some difficulty with Chapter 6. Let me explain why: I don't like front-wheel drive, four-cylinder cars. They don't drive right and they have half an engine. No matter how much peak power the engine makes, it still drives like half an engine. That said, I did find this chapter useful. I learned quite a bit about refinement in manual transmission design, as well as front-wheel drive technology. Honda — regardless of a lack of displacement and cylinders in their engines — has very refined designs. Now, I have no way to tell how complete or incomplete the information is since I've never broken the case on a Honda transaxle...or any transaxle for that matter. In fact, I hadn't even seen a Honda transaxle before this, but it appeared to be written every bit as well as the T5 section.

Chapter 7: Modifying Manual Transmissions

Although modification is discussed throughout the book, Chapter 7 gets into the specific modifications you can do to improve different aspects of various transmissions. It also has a section on transmission swapping that covers a number of different options for the various makes of cars, including a unique five-speed swap I was unaware of: a Toyota/Aisin transmission into a Chrysler V8 chassis. When I was done reading it, I found myself taking away from the chapter a much clearer idea of what I could do to improve the holding capacity and performance of a transmission, which will help me when increasing the performance of any of my engines. It has also given me a better idea of how to evaluate components or transmissions when choosing them for a modified application. In the case of my '93 Mustang, this has been very beneficial because my future plans for it hinge on exceeding the capacity of most transmissions, yet I still want to use it on the street without resorting to all-out race modifications such as dog rings and straight-cut gears.

Chapter 8: Clutches and Flywheels

Up to this point, my clutch and pressure plate knowledge have been very limited. I understood the basic function of them, but nothing of the design parameters or strengths and weaknesses of the various types. After reading this chapter, I can easily say that my knowledge has increased ten-fold. Although I don't think I know everything there is to know, I think I can make a sound judgment on what type of clutch and pressure plate are well suited to an application as well as when to upgrade from a stock setup. It was also nice to read about the effects of bellhousing alignment on the transmission and how to correct for those problems.


Overall, I learned a lot from this book. It was well written, easy to read, and left me jonesing to go out and rebuild the transmission for my '93 Mustang. The best part is I feel much more confident about being able to make sound judgments for part replacement and proper setup. I'd highly recommend this book to anyone who wanted to rebuild their own transmission or who wanted a better idea of what to look for when having their's rebuilt.

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For more information contact Motorbooks on the web at www.motorbooks.com, by phone 1.800.826.6600, or by email at customerservice@motorbooks.com.

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