Chevyhiperformance.Commaximum horsepower for digital drivers
Access To Automotive Parts AndservicesTech tips and how-tos
Search for archived articles and photos
E-mail your tech questions to us at carcraft@primedia.com (include the words "What's Your Problem?" in the subject line) or fax them to 323/782-2223. All correspondence must be signed with the sender's real name (not a nickname or a screen name) and include the sender's hometown and state or province. While mail cannot be answered personally, Car Craft will publish as many letters and replies as space permits. Photos are welcome, but no materials will be returned.
Rear Gear ReduxI have an '88 Mustang LX with the 5.0L engine and T5 five-speed manual trans. I've owned the car for about a year, and I've been experiencing a drivetrain vibration that's getting really annoying. I've been told by a few friends that the problem is probably the rearend gears. A previous owner replaced the stock 2.73s with aftermarket 3.73s, and I can hear them whine whenever I drive over 40 mph. The vibration kicks in at slightly higher speeds.
My actual question is, can I use used gears? I can get a set of Ford Motorsport 3.55s that a friend had in his Mustang for only a month or so before swapping up to 4.10s. He says when he had his gears installed, the tech-a Ford dealership mechanic-told him that the Ford gears could usually be installed by simply bolting them in, while keeping the shims in the same place. Allegedly, the car made no gear noise afterwards. Do you think I could bolt the gears into my Mustang with success? Or do I have to have them set up professionally? Tim GeffertHanover, PA
It sounds like you have more than one issue to deal with, Tim. Although the whine you hear may well be coming from the rear gears, it is unlikely that they are also the source of the vibration. Let's address the gear issue first.
Your Mustang's rearend gears were probably not installed properly, and that's the likely cause of the whine you're hearing, whether they were aftermarket or not. The Ford 8.8-inch rear-axle assembly, as found in all '86-and-later 5.0L Mustangs, requires that the installer set pinion depth and backlash between the gears, usually with a crush collar or shims on the pinion, and more shims between the carrier and the housing. This procedure requires precision measurements for successful results, though bolting the gears in without checking anything is physically possible. We've also heard tales from experienced Ford wrenches about bolting in new gearsets without having to move any of the shims around, but this was back when the cars were new, and even then, luck probably played a big role. Most axle shops will set up gears for around $150-$200 for a common axle like the 8.8, and that's money well spent, since operating the vehicle with new gears for any length of time establishes a wear pattern, which then negates later attempts to quell any gear noise with further adjustments. For this reason, your used 3.55s may not eliminate the rearend noise. There is the possibility that those gears were set up properly during the first installation, and that your current installer could also attain the proper gear positioning, but he would have to take the time to establish the same wear pattern to ensure there was no noise and that the gears continued to wear properly-most won't take the time with used gears, and fewer will guarantee the work. Ford Racing's gearsets are relatively cheap, so it's probably worth stepping up to a fresh set.