Replacing The Driveshaft
The newest 2nd generation RX-7 is already old by most people's standards. As with any older car, there are some standard wear items that are either already worn out or are on their way. One of these items are the u-joints on the driveshaft. If these joints are worn, the common symptoms are a horrible vibration while driving. This vibration cannot be cured by balancing the wheels, alignments or any other means. If the driveshaft is loose under the car, the u-joints are worn.
Unfortunately, Mazda decided to skimp on the driveshaft and gave us one without replaceable u-joints. So, you have two choices: 1. Use the stock shaft to replace the worn one, 2. Use an after market shaft. Using another Mazda shaft will fix the problem, but will be expensive and eventually the joints will wear out again, requiring replacement. An after market shaft will likely be cheaper, and have replaceable joints. I chose an after market shaft when I did mine. I had a local driveline shop build it for around $350. Mazdatrix sells an after market shaft with replaceable joints if you do not have a local shop.
Parts Required
- New driveshaft
- Lock washers to fit flange bolts
- Step 1 - Lift the car
- The easiest way I've found lift a car for the home mechanic is to simply use jacks and jack stands. Use the jacks two lift the car and set it on jack stands. The jack stands should be positioned under heavy frame members such as engine cross members, the rear differential brace or the differential itself. Do not used regular jacks to support the car will you are under it as doing so is just an invitation to be crushed. Car ramps can also be used but can be more awkward to set up, especially if you are lacking floor jack. And you will need to be able to rotate at least one rear wheel.
- Step 2 - Remove rear exhaust
- Remove the two bolts that hold the rest of the exhaust system to the catalytic converter. These bolts may be rusted, so use lots of penetrating lube. Now, detach the exhaust hangers from the Y pipe. This can be annoying, so use some penetrating lube and a screwdriver to pry things apart. If done right, you will not damage the hangers. At this point, the only section of the exhaust attached to the car will be the mufflers. You can either remove the hangers that hold them to the body, or just let the whole thing hang.
- Step 3 - Remove the shaft
- Wedge a screwdriver into the rear u-joint to hold the shaft stationary, then remove each bolt. You will have to rotate the shaft to get to each bolt, so put the transmission in neutral and rotate one of the rear wheels to move the shaft around. After taking off the last bolt, be aware that the rear end of the shaft may drop. With the rear disconnected, angle it down and then pull the front out of the transmission.
- Step 4 - Install new shaft
- Smear some transmission fluid onto the new shaft yoke to prevent damaging the oil seal, then slide it into the transmission. This is the most annoying part, as all the splines must line up. It helps to have another person to hold the shaft up. With the new shaft in the transmission, line it up with the flange on the differential and install each bolt loosely. Use new lock washers. With all the bolts in, rotate the shaft and tighten each bolt to 36 to 43 lbs if your car is earlier then 1989, or 49 to 50 lbs if it is later than 1989.
- Step 5 - Reinstall exhaust
- Lift the exhaust back up and bolt it to the catalytic converter, then reinstall the hangers. You may want to use a new gasket to eliminate the possibility of leaks.
- Step 6 - Lower car and test
- Lower the car. Start it up and let it warm for a minute or two and then go for a drive. Be gentle at first until you are sure there are no problems and then drive it normally.
Notes
1. Remember to keep that new shaft properly lubed so those joints last!
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