How to Start a Ford Transmission Rebuild Project: C4 and C6

Before embarking on your Ford C4 or C6 transmission project, you’re going to need to equip yourself with a proper work setting and tools necessary to do the job. Because automatic transmissions encompass dozens of tiny parts—clips, balls, pins, valves, springs, and other items—your workspace must be well-lit, neat, orderly. “Hospital clean” is an abused term, but it is appropriate in automatic transmission building. Even the smallest particle of dirt can disturb an automatic’s precision tolerances, causing undesirable results and failure.

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Safety Equipment

As in any other area of an automobile, automatic transmission building poses its share of safety hazards. You’re going to be exposed to all kinds of toxic chemicals, which calls for hand, face, eye, lung, and ear protection. You’re going to need nitrile rubber gloves, which are similar to latex types used in hospitals, to protect your hands from harsh chemicals. Solvents can dry your skin and pose a certain cancer risk. You also want to protect your skin from sharp edges. Iron and aluminum castings have their share of sharp edges, as do stamped sheet-metal components. Iron and aluminum particles can penetrate your skin and cause pain and infection.

 

 

High-frequency noise from power equipment can damage hearing, which calls for earplugs or muffs. Even the low-decibel din of shop equipment, electric motors, gear and belt drives, air compressors, and the like, damage hearing with exposure over time. Cleaning and drying parts with compressed air, which isn’t always recommended, is loud enough to damage hearing.

Eye protection is paramount. Use goggles or safety glasses to protect your eyes from flying debris. Use wraparound goggles that keep debris well away from your eyes. Protect your face with a good face shield. Welding, for example, requires specialized eye protection to prevent permanent retina damage and sight loss.

 

Safe shops are outfited with proper personal protection gear such as ear, eye, respiratory, and skin protection. Hearing loss can be directly attributed to loud noises, such as power tools and compressed air. Compressed air is probably the single greatest source of hearing loss and personal injury. Never use compressed air for horseplay.

 

 

Whenever you use harsh chemicals such as petroleum or alcoholbased cleaning solvents, protect your lungs with a good respirator. I see dust masks used occasionally—dust masks are not enough. A good respirator keeps all chemicals and particulates out of your lungs. The same rule applies to spraying paint. Always use a respirator, no matter how well ventilated your shop or driveway is.

 

A Place To Work

It is impossible to successfully rebuild an automatic transmission on your filthy garage floor or workbench, nor can you do it with an inadequate tool crib. You must have a clean, well-lit shop with a workbench. Dust and dirt are an automatic transmission’s worst enemies. A tiny grain of dirt or sand damages or locks up an automatic transmission’s precision parts.

Think of an automatic transmission like a Swiss watch—perfectly mated surfaces must have perfect tolerances. Clutch frictions and steels must mate precisely and smoothly. Sliding valves must glide through the valve body smoothly. Servo pistons and seals must be clean. When there’s dirt, these parts bind because tolerances are extremely tight in order to provide proper containment of hydraulic pressure.

Seals can also be damaged by dirt and friction material, which causes internal hydraulic leaks and failure.

When you’re not working on your transmission, keep it wrapped up tight inside a large heavy-duty plastic trash bag.

Your tool collection should include some type of transmission support fixture for both disassembly and build-up if you can afford it; it’s much easier than building a transmission on your bench. Transmission shops typically have cobbled up holding fixtures made from transmission cases and shafts. There are also holding fixtures you can purchase from tool supply houses such as Harbor Freight, which offers cool shop tools for all kinds of operations at affordable prices.

 

Regardless of the kind of automotive repair work you do, you must have a neat, clean place to work. Automatic transmissions are precision components that call for a clean working environment with a place for everything. You’re going to need containers for small parts and you must have a hospital-clean work surface.

 

You need an air compressor for air-tool functions, blowing out passages, and checking servo and clutchpiston function. Air leaks, when pressure is applied, tell you there are potential fluid leaks around servo and clutch-piston seals. The absence of a telltale click of a control-valve piston, when air pressure is applied, means something’s amiss. Air tools also speed up the process of transmission disassembly and build-up. Good advice: always use a torque wrench (inch-pounds and foot-pounds) on all fasteners when it’s time for assembly.

 

Tools of the Trade

There are tools in the automatic transmission trade you need to be familiar with: slide hammers, snapring pliers, mallets, tiny screwdrivers, awls and picks, presses, punches, bushing drivers, slide calipers, seal installation tools, roll-pin removal tools, alignment pins (made from old bolts), seal drivers and installers, Torx drivers, and more. Some of these items can be rented or borrowed, especially if you intend to do a transmission build only once. With others, you have to bite the bullet and buy them if you want to rebuild a transmission yourself.

 

Sears Craftsman combination wrench sets continue to have a lifetime guarantee, as do Snap-On and MAC tools, which makes them a good investment. When you invest in expensive tools, keep them in organizers like this one for good tool inventorying.

 

When it’s time to wash parts, you’re going to want a basket with holes smaller than your smallest parts. With automatic transmissions, this can be tricky because items like check balls have a way of slipping through.

 

A good combination wrench set ranging in size from 1/4 through 1 inch should cover your needs. Avoid this kind of confusion and buy a matching combination wrench set with both SAE and metric sizes.

 

Harbor Freight is an outstanding bargain these days, with high-quality tools for not much money. Harbor Freight’s Pittsburgh Pro Series tools are of good quality at bargain prices, which makes them a great value.

 

Although automatic transmission building calls for specialized tools, most of the tools you’re going to need are simple hand tools you can buy from Harbor Freight or Sears. Here’s a good basic list of what you need:

 

• Combination Wrench Set (SAE), 1/4 to 1 inch
• 1/4-inch-drive Deep- and Shallow-Well Socket Set
• 3/8-inch-drive Deep- and Shallow-Well Socket Set
• 1/2-inch-drive Deep- and Shallow-Well Socket Set
• 3/8-inch-drive Speed Handle
• 3/8-inch-drive Breaker Bar
• All kinds of socket extensions of various lengths and sizes
• 3/8-inch-drive Torque Wrench (foot-pounds)
• 1/4-inch drive Torque Wrench (inch-pounds)
• Common and Phillips-Head Screwdrivers (all sizes)
• Awl and Pick Set
• Mallet
• Ball-peen Hammer
• Punch Set
• Tap and Die Set
• Thread Chaser
• Pliers
• Needle-nose Pliers
• Duck-bill Pliers
• Snap-ring Pliers Set
• Channel Locks
• Vise-Grip Pliers
• Putty Knife
• Wire Brush
• 4 Large C-Clamps (work just as well as a clutch pack assembly fixture)
• 55-Gallon Trash Bags (to use as dust covers)

 

Most professional transmission shops have transmission holding fixtures to support transmission cases during disassembly and assembly. Not many of us can afford such a fixture or even need it more than once. This calls for a hard work surface on which to build your C4 or C6. Although you might feel like you need a holding fixture, it really isn’t necessary for the home garage technician. Where transmission disassembly and assembly gets tricky is when it is in the stack position and it’s time to load components. I’ve seen some transmission shops use tailshaft housings as holding fixtures. Alternatively, you can always bore a hole in your workbench for a stack assembly. Places like Harbor Freight offer inexpensive holding fixtures, designed for most transmission types, that work well for disassembly and assembly.

Rebuilding any automatic transmission calls for compressed air. You need it for removing parts such as clutch pistons and sliding valves. You’re also going to need it to clear passages. During assembly, you need compressed air to check component function. You need a huge industrial compressor; a 10- to 30-gallon compressor that operates off 110/115/120 vac produces the volume you need. And getting 220-vac power for more powerful compressors isn’t always easy in some places.

Air tools make transmission building faster and easier. You’re going to need a 3/8-inch-drive air wrench and ratchet. A 1/2-inch-drive air ratchet is overkill for automatic transmission repair. If you’re going to use an air grinder, take extra care not to damage cast aluminum contact surfaces.

 

 

An air blowgun is useful for clearing passages and for disassembling clutch packs and servos. It is also useful for doing operational checks on clutch packs, servos, and control valves. Always use eye, face, and ear protection whenever you use an air blowgun.

 

You’re going to need a variety of pliers ranging from conventional to needle-nose to duck-bill. Vise-Grip and channellock types are also important to your transmissionbuilding tool inventory.

 

Snap-ring pliers are a must for transmission building— both internal and external types.

 

Snap-rings in automatic transmissions don’t always have holes for snap-ring pliers. Make life easier by investing in convertible snap-ring pliers for all applications. You may also invest in a full-scale snap-ring pliers set such as the OTC 4512 set.

 

Sears offers the greatest selection of high-quality screwdrivers anywhere. A nice thing about Craftsman screwdrivers is color and feel, so you know by feel whether you’re holding a common
or a Phillips screwdriver. These screwdrivers are rugged and last a lifetime.

 

A speed handle makes light work of disassembly and assembly, enabling you to remove and install fasteners quickly.

 

Like the speed handle, air tools make tedious work go quickly. Never use an air tool to tighten fasteners. Use a calibrated torque wrench and be confident.

 

It’s always good to have a bench grinder with a wire wheel for clean-up purposes. This is why eye protection is so important.

 

Rather than use a hammer like this one, go with a good ball-peen hammer and a 5-pound sledge. Know when to use a hammer and when to try something more gentle.

 

A tap-and-die set is a wise investment because it serves so many purposes. Transmission disassembly can involve damaged fasteners, pulled threads, and a lot of other problems where a tap-and-die set comes in handy. Invest in a good thread chaser set while you’re at it, for clean threads and accurate torque readings.

 

Transmission building calls for the use of punches from time to time. I’ve found the best punch set comes from Snap-On. Sears is the next-best option but only in highcarbon steel. Go with high-carbon steel punches, and wear eye and face protection.

 

Precision screwdrivers are something every home garage technician should have because they’re good for tight spots. You may need them for valve body service issues and small seal removal.

 

I cannot overstress the need for precision measuring tools like calipers, thickness gauges, and the like for checking endplay and critical dimensions.

 

Invest in a complete set of high-quality drill bits and a drill bit sharpener. Few things frustrate more than a dull bit. And know the proper speed to drill—slow and easy along with lubrication is the best way. Have a couple of wire wheels on hand for clean-up purposes. Don’t forget your eye protection.

 

This is a clutch spring compressor common to transmission shops. However, four C-clamps accomplish the same thing in your home shop.

 

Picks and awls are handy for so many purposes, such as removing and installing C-clips or removing old O-rings.

 

A compressed-air nozzle is useful for blowing out passages and performing function tests. Compressed air enables you to check servo and clutch-piston function. You may also check control-valve function with compressed air.

 

This lip seal tool makes it easy and safe to roll in rubber seals without damage.

 

Fastener removal tools are very useful for stubborn fasteners seized to cases. Splash on plenty of WD-40 first.

 

Keep an oil can full of transmission fluid handy for lubricating parts and seals, and filling front pumps.

 

A set of seal-and-bushing drivers are affordable and every home garage should have one. Check out Harbor Freight for yours.

 

Although this is an older high-end torque wrench, it’s a reminder that your garage should never be without one. You need both inch-pounds (3/8-inch drive) and foot-pounds (3/8- or 1/2-inch drive) for transmission work. Most of the time, you need inch-pounds—never get the two mixed up.

 

A universal transmission holding fixture is a nice touch for any garage and they don’t have to be expensive. The more custom types get expensive.

 

A front pump puller is for just about any type of automatic transmission. But honestly, you don’t need one. Most front pump assemblies pull with an aggressive yank. You may also work the front pump loose from inside your C4 or C6 with a large common screwdriver and caution.

 

Of course you’re never going to have one of these in your garage, however, your local transmission shop should have one. A Hot Flush system (left) purges transmissions and coolers of stray particulates that can damage new transmissions. The Hot Flush system does a powerful two-way surge that dislodges clutch material and metal particles, catching all of it in the filter (right). This one belongs to Tom’s Transmissions.

 

Because automatic transmissions have dozens of tiny parts, organization is very important. In my home shop, I use small, disposable kitchen containers and mark them for identification. Cooking sheets are also a good idea for larger parts like fasteners and can be reused. Good old-fashioned coffee cans are good for cleaning parts. Lacquer thinner and brake cleaner are the best solvents because they have a high evaporation rate. Petroleumbased solvents are also good because they minimize the risk of rust and corrosion and make excellent grease cutters. When the heavy crud is gone, lacquer thinner and brake cleaner are good for final prep work.

For cleaning items like the main transmission case, tailshaft housing, and bellhousing, dishwashing detergent and a high-pressure washer work very well. A pressure washer can be rented or purchased for a modest amount of money.

Although hammers occupy most toolboxes, you’re also going to want a hard mallet for things like servo covers and pistons. A mallet provides passive-aggressive force without inflicting injury. However, if you have to force any component, ask yourself why. Although servo covers and pistons must have a snug fit, installation by force means something’s too tight or you forgot to lubricate seals and parts.

Written by George Reid and Republished with Permission of CarTech Inc