June 11, 2010

Strong Like Bull
I want to upgrade the suspensions on my early Mustangs and right now I am leaning toward the Rod & Custom frontend, but am still not sold on them because I have questions on strength issues. I think that I would still want crossbraces in the engine compartment. I would really like to see a head-to-head comparison of all the suspension modifications to see how they work out.
Doran Archuleta
Via the Internet

A Upgrading your front suspension for the best end gain really depends on what you intend to do with the car, and one of the reasons why a head-to-head article is difficult. There are so many choices now for early Mustangs: coilover, tubular, Mustang II, McPherson strut, double A-arm, and the list goes on. All these systems have their advantages and disadvantages. Some are better for daily driving, some are better for performance, some are better on your wallet. Most are a combination of several things, but no system fits all applications. Don't forget that no matter who makes the suspension, they all compromise somewhere to fit within the confines of the original Mustang frame-rails, fenders, shock towers, and so on.

If you're looking for a smooth street car, I generally suggest a good stock rebuild with Moog or TRW components (I've had trouble with offshore-supplied parts in the past-stick with good, quality stuff) and an aftermarket rack-and-pinion system. This is the best driveability combo for a street car with the least impact on your wallet. You don't need to spend extra money for something more. For street/strip/track cars, the options open up; now you want to look for systems that correct some of the problems with the original suspension geometry (most tubular systems do this like the Griggs setup shown here) and work well with rack-and-pinion steering. Strut systems are good choices too.

As you get closer and closer to all-out performance suspensions, here's what I tell people: Find out who's winning in the performance arena you're planning to race in and use their products. If a company has cars out winning races with its products, the company will make sure you know about it, and its ads aren't just a bunch of fluff. And remember, drag racing suspension works differently than road race suspension. Decide the end use for the car and then pick a suspension that works well for that application. I've installed the Rod & Custom system in the past-it's a quality kit and the components are expertly made. You have nothing to worry about. Good luck with the projects.

The Whatchamacallit
To some of us Ford guys who have been around since 1957 and know all about Ford's 8- and 9-inch removable third member differential carrier, we know it's not a vegetable and does not have seeds. So, why do people continue to call this chunk of iron a pumpkin? Can you clear this up and get them straight?
Greg Plubell
Garland, TX

A I grew up in SoCal, so I always called them center sections. I hope that doesn't make me a heretic. I guess they are called pumpkins because when they are laying there getting that nasty smelling locker additive all over your garage floor they kind of look like a pumpkin (and they turn orange when they rust). Call them differential carriers, center sections, pumpkins, hog heads, or gearsets, the key is that we know what they are talking about.

Since you're from Texas, you'll understand all about regional differences. In Indiana we measure things by miles (45 miles west of Indy). In California we measured things in time (45 minutes west of Thousand Oaks-which is only about five miles due to traffic). Texas is too big for either miles or minutes so it uses "right near" and "a right far piece." A true Texan can show or point out the general direction of "yonder" as well.

Gauging Reaction
I have a '69 Mach 1. I recently had a 3.55 gear put in, replacing a 3.25 gear. My transmission is an FMX. Can you tell me what tooth count speedometer-driven gear I would need? I currently have a 19-tooth gear. Second, I recently replaced the light bulbs in the instrument panel. I replaced the old laminated circuit board/harness that connects to all the gauges too, as it was cracked in a few places. All light bulbs work, however none of the instrument gauges are working. Any suggestions what to look for?
R. Hestad
Via the Internet

A To figure out the correct speedo gear we need to know what size tires you are running. The speedometer-driven gear (the one on the end of your speedo cable) tooth count is determined by the tire diameter, rear axle ratio, and the number of teeth on the speedometer-drive gear (the one on your FMX output shaft-which is machined in the shaft and has eight teeth). We know the drive gear and rear axle ratio, but we don't know the tire diameter.

Here's the formula for calculating the correct number of teeth for your speedometer's driven gear:

Drive Teeth x Axle Ratio x Tire rpm = Driven Teeth

To calculate the tire revolution per mile you use this formula:

Tire Rev. per Mile = 20,168
Tire Diameter (inches)

So, if you were running a set of F60-15s on your car, the tire revolutions per mile would be 20,168/25.9 inches (the diameter of an F60-15) = 778.69. Punch that into the above formula (8x3.55x778.69)/1,001=22.09 teeth. So a 22-tooth gear would get you the closest to the actual speed.

One thing to note, it sounds like your car has already had a gear change. The 19-tooth gear is a C6VY-17271-B and should be tan in color. This gear is for the 15-inch tire setup and not the original E78-14 or optional E70 or F70-14 tires. The E78-14 and F70-14 tires would have had the C8SZ-17271-B 20-tooth orange gear; E70-14 would have had the D0OZ-17271-A 21-tooth purple gear. So you may luck out and already have the right gear, pending your tire diameter size of course.

Concerning your question on the gauges; the light and gauges on your car are fed from different power sources in the printed circuit board connector. The blue with red stripe wire powers the cluster illumination, and the gauges are fed by the purple wire, which, in turn, is connected to the constant-voltage regulator. The constant-voltage regulator is the square box on the back of the gauge cluster that plugs into the printed circuit board via the 9-volt battery style connectors. This regulator maintains a constant 5 volts to the gauges and is on a separate line because the regulator can cause radio noise. They put a choke resistor on this wire to prevent the noise from occurring. My guess is that your regulator is bad, or not hooked up. I've had problems with some of the replacement solid state regulators that are on the market, so if you put a new one in, you might try going back to the original and see if that cures the problem.