1970 Ford Fairlane - Bulletproof C4

You almost have to feel sorry for the transmission. In the grand scheme of things, it always ends up playing second fiddle to the engine behind which it resides, and that really isn't fair-especially since the engine would be nothing more than an expensive noisemaker without it. If you want your ride to get down and boogie at the track, choosing the right transmission with the proper internals and torque converter is critical.

Our '70 Fairlane project car came from the factory with a utilitarian 302 small-block and a C4 three-speed automatic. When we first peered under the big Ford, we were struck by how small the C4 trans looked. To us, it seemed far too dainty for a performance transmission. Of course, we were wrong. Turns out the C4 can be built to hold a boatload of torque, and it has the added benefit of being lighter in weight than the portly C6. Given that we'll eventually be running a 408 small-block, sticking with a C4 trans seemed like a smart move: we keep the weight benefit, and installation will be a direct swap.

The big question is how much massaging a C4 requires to hold more than 500 ft-lb of twist. Rather than guess, we called Hughes Performance to find out what would best fit a street-guy budget like ours. We found there are many ways to build a performance C4. Knowledge is power if you want a unit strong enough to fit your application, yet not filled with expensive parts you don't need. We're all familiar with the mechanics of the internal combustion engine, but the functional workings of an automatic transmission fall toward the fuzzy side. To fill our brain with the ins and outs of the C4 tranny, we headed to the Arizona desert for a build session with Hughes Performance.

Here's our Fairlane's street/strip C4 and converter from Hughes for $1,095 (PN 26-1). We opted for the deep trans pan (PN HP5180P, $152.75) and a six-pinion front carrier (PN HP5268, 259.65), which brings our total to $1,507.40. The 10-inch 2,800-stall converter costs $345.25, and our SFI-approved 164-tooth flywheel set us back $198.25. Total cost for everything: $2,050.90. Combined, these parts will put our Fairlane project squarely into the 11-second zone without any problems.

This six-pinion front carrier, or planetary, is an upgrade to Hughes' street/strip C4 transmission, since the extra planetary gears-stock has three-spread the load over a greater surface area, making it much stronger (PN HP5268, $259.65). It is recommended if you plan to run 11s or faster, and there's no downside if you plan to race hard and have the extra cash.

Here are the three most common servos. The far left is the "B" version, found on lower-end factory C4s. "A" is in the middle, and is the stronger, factory version. (All Hughes performance transmissions ship with the A version.) On the far right is the billet servo (PN HP5270, $184.80); it's stronger than the A, and is always in stock.

The tan clutch discs are stock replacement BorgWarner units. All Hughes transmissions use the Alco red clutches, as they're harder and can take more heat compared to the stockers. This means they will last longer and hold better.

Another Hughes C4 upgrade over stock is the bands. On the left are the OEM-style paper bands, and on the right are the upgraded Kevlar bands. Like the clutches, the Kevlar bands can take more abuse, and they hold up much better than paper. The C4 uses two bands: one rigid and one flexible.

Unlike a GM transmission, the input shaft on a C4 is pretty stout. On the left is a 24-spline stock unit found on early C4 trannys. It's only used when requested by the customer, typically for a restoration project. In the middle is the 26-spline OEM shaft, which is included in Hughes' street/strip C4 and is plenty strong for most apps. The billet shaft on the right is an upgrade recommended on full-race C4s running a transbrake (PN HP5214, $197.65).

You have two choices for a bellhousing: the larger one on the left is from later-'60s to mid-'70s cars, accepts a larger flywheel, and is generally supplied by Hughes; the smaller bell on the right is the early version, and is only used when the customer wants a correct restoration, or if space is critical. The larger bell is also the perfect choice if you want to ditch the AOD in your Fox Mustang and switch to a C4. Hughes offers SFI-certified bellhousings and shields if you need it to pass tech.

Steels are another area in which you can upgrade over the base offering. The one to the left is a stock steel, and the right is a Kolene-treated steel. The Kolene steels can take more heat than the stock steels, but they are also slicker and have less "bite." Generally, you only need the Kolenes in high-power race applications, and Hughes can help you decide if your ride warrants such an upgrade. Ours didn't.

At the right is the stock pan found on 99 percent of all C4s, including our Fairlane. In the middle is a deeper OEM pan, but it only came on a few vehicles and is hard to find. A better solution is the deep cast-aluminum pan on the end. It's an upgrade (PN HP5108P, $152.75), but worth the extra cost since it seals better, holds more fluid, and has a drain plug with a magnet.

On the left is a standard direct drum, common in six-cylinder applications; on the right is a V-8-style drum. The internal notch (red arrow) is much higher on the right drum, so that more clutches can be used. Since more clutches equate to more holding power, this is a good thing. All Hughes transmissions use the V-8-style direct drum.

Here is the sun shell for the C4. Unlike the lightweight units found in GM transmissions, this stock unit is good to go-including high-power applications. In fact, there isn't even an upgrade option on the market.

The valvebody is the brains of the transmission-it tells the trans when and how hard to shift, and it determines how the C4 operates. The smaller yellow spring is used when a gentler, more factory-like shift is desired. The larger green spring provides a firmer shift and is used on most Hughes C4 transmissions. Hughes also replaces several other springs in the valvebody, and changes the configuration of the internal check balls.

The only modification Hughes makes to the circuit plate is slightly enlarging two orifices (red arrows). Hughes' transmission expert told us, "A shift improver kit recalibrates the valvebody to control shift timing and firmness. By adjusting the shift timing, you can get the trans to shift earlier or later, based on road speed. Shift feel is the duration it takes to make the shift; quicker is firmer, and slower is softer."