I agree, nothing adds to the performance of a vehicle more than a gear-ratio change. Depending upon the type of driving, I also prefer 3.50:1 gears for a street-driven vehicle. They yield plenty of torque for off-the-line performance yet allow decent highway driving as well. Anything numerically higher would make highway driving unpleasant, as the higher rpm would create unwanted interior noise and would kill fuel economy.
A limited-slip differential is not necessary for a street-driven car unless there's a need to tie both rear wheels together. Under most street conditions, both rear tires have an equal amount of traction, therefore even an "open" differential will apply equal torque to both rear wheels. However, if traction is limited or lost on one wheel, an open differential will send all the torque to that side, forcing that one tire to spin. A limited-slip would send torque to both rear wheels regardless of traction conditions. A drag-racing-style start will cause one tire to lift slightly, creating unequal traction to the rear wheels, thus a limited-slip differential would help in this situation. For ordinary street use, an "open diff" will suffice; but for drag racing, fast starts, or inclement weather, a Posi-traction type of differential is the answer.
Door Speaker PlacementI have a '70 hardtop, with a standard interior, that came with a few options like a C4 automatic transmission, a 302 2V, and A/C. I've been restoring it with the intent of keeping a stock appearance, but I've been upgrading it with some of the factory options like power disc brakes and center console. I picked up an original AM/FM stereo I would like to install with the standard speaker locations in the doors, but I'm not sure where the cutouts would go. I've searched the Internet, but have not found any help. Are there any templates available that show the proper hole locations?Perry ThuenteNaperville, IL
The speaker location is not super critical, therefore a template is not absolutely necessary. Basically, the speakers were mounted with their centers in line with the window cranks. A quick look at some photos and other Mustangs at a car show will give you the general idea. If your car has a deluxe interior, the back of the door panel may have an outlined area that's to be removed so it would be open to the speaker. It's important, however, to be certain the speaker will not interfere with either the window regulator mechanism or the glass. With the door panel removed, pick the spot where you feel the speaker should be, hold the speaker inside the door, and carefully operate the window to look for proper clearance. A small adjustment one way or another will not affect the overall look and may be necessary, as the dimensions of various speakers will vary. The speakers and grilles are available from most Mustang parts vendors and they can coach you on the correct size speaker.
Export BracingI'm planning to install an export brace in my '69 Mustang coupe and would like to know if it mounts below or above the mounting bracket on the firewall.Mark S. von WehrdenVia the Internet
The export brace mounts above the firewall flange and is a direct drop-in for your coupe. I highly recommend the addition of an export brace on a '69-'70 Mustang to strengthen the weak shock towers. These cars really respond to the additional support. If the brace does not fit between the shock towers, the towers have begun to move toward the center of the vehicle and must be spread out. This may require some muscle and may be accomplished with prybars between the export brace and shock tower. I usually remove the hood and jack up the car in the center, under the bolt-in crossmember, to allow the weight of the hanging suspension to help spread the towers. A stubborn vehicle may require the use of a hydraulic "Port-A-Power." Remember, the export brace is dimensionally correct, but the shock towers may require some "coaxing."