Making the Shift to RX-7 Clutch Work, Lou Calka, Jr., Brake & Front End, February 1999

Many people seem to think that Mazda’s RX-7 is an "untouchable" because of its unique rotary engine. While the engine is certainly different, you can’t say the same while standing underneath the car. The brakes, transmission, differential and suspension are all pretty much conventional.

The RX-7 is no longer in production, although it went through three "generations" of body styles. The first generation car was sold as a 1979 model, though some were available in ‘78.

The first generation ended in 1985. A carbureted, 1.1 liter "12A" engine was used throughout those years with a fuel injected, 1.3 liter "13B" engine installed in the ‘84 and ‘85 GSL-SE models. The second generation was from 1986 through 1991, when the car got larger. The 12A engine was dropped entirely in ‘86 and a turbo version of the 13B was introduced in ‘87.

Although cars were sold in ‘92, there was no ‘92 model year. The third generation was unveiled in ‘93. The third generation was short lived, as Mazda (or more likely, Ford) pulled the plug after the last ‘95 was built. "Gen 3" cars were smaller, had only a twin turbo 13B, and cost about five times as much as the ‘79. But essentially, clutch service is the same for all generations, except for the parts prices.

The slave cylinder is mounted on the top of the bell housing, near the oil filter, with two 12mm bolts. (‘93-’95 slaves are at the left side of the bell housing, best reached from underneath.) Squeeze the boot to check for fluid leakage.

Wet fingers mean a new slave cylinder is in order. Replace the cylinder and bleed the system. Corrosion is a problem and the cylinders are inexpensive. So don’t waste your time trying to put a kit in the cylinder, it doesn’t save much money and it’s not a long term fix, even if you hone it. The slave cylinder is connected by a flexible rubber hose to tubing running along the firewall to the master cylinder. Check the hose for damage, but the hoses are not problematic.

Sometimes the clutch master cylinder will leak externally. If it does, the fluid will leak into the driver’s footwell area where it will be absorbed by the padding and insulation under the carpet. Always check both the master and slave cylinders for leakage if the reservoir is low. Although the slave fails more frequently, now that these cars are getting older, we’re finding more master cylinder problems. A sinking clutch pedal, (like a bad brake master cylinder) without fluid loss, is always a bad clutch master cylinder. The customer may complain that the car creeps forward or stalls if he’s in the habit of waiting for traffic lights with the car in gear and his foot on the clutch.

While the clutch has no freeplay adjustment (the long bore of the slave cylinder compensates for clutch wear), there is an adjustment you need to be aware of when replacing the master cylinder. The clutch pedal operates the master cylinder via an adjustable, two piece threaded rod with a jam nut. After installing the master cylinder, the clutch pedal should move a quarter inch before the rod starts to push the piston of the master cylinder.

Bleeding the system is quickly and easily accomplished with two people, but since the pedal will stay on the floor at the end of a stroke with the bleeder open, you can do it by yourself.

Fill the reservoir, open the bleeder on the slave cylinder, and have an assistant depress the clutch pedal to the floor. Close the bleeder and pull the clutch pedal back to the top of its travel. Repeat the procedure until no bubbles come out of the bleeder screw. Don’t take the bleeder screw out of the cylinder.

Some early models use a flat end instead of a taper on the bleeder screw. The flat part presses on a small steel ball that does the actual sealing. If the ball falls out, the bleeder screw won’t seal at all.

The next most common problem is clutch slippage. Since the system is self adjusting, slipping is an indication of a worn out clutch. Depending on driving habits, clutches can wear out in as little as 60,000 miles on early models. Average wear is more like 80,000 or 90,000. Clutch replacement obviously requires transmission remove and repair, which is fairly straightforward. The ‘93-’95s have a few more pieces, such as a Power Plant Frame (Mazda’s term for a ladder type bar that provides a solid link between the differential and the transmission), but all models are similar, especially the first and second generation cars. We’ll concentrate on Gen 1 and 2.

Transmission removal starts inside the car by unscrewing the shift knob. Then, carefully pry between the plastic plate that surrounds the shifter and the console. The console does not have to be removed. The boot is attached to the plastic plate, and I’ve seen more damage done than I care to mention by people pulling on the boot itself instead of removing the plastic plate.

With the plate out of the way, pull the next round boot up from around the shifter to expose the three 10mm bolts which retain the shifter. Pull the shifter straight up out of the transmission. Note that there is a plastic bushing and wave washer on the top of the shifter ball and one below, in the transmission itself. If the shifter seems extremely sloppy, the bushings are the most likely cause. While Mazda lists a part number for the top bushing (as a kit with the wave washer, flat washer and gasket) as part number 8AF1-17-481, for about $6, they service the lower bushing with the aluminum shifter housing for a whole lot more. Some transmissions have no lower bushing, because the ball of the shifter rests directly in a machined aluminum area of the transmission. If the lower bushing is blue, use the part number above. If the bushing is white, use part number M505-99-178. Pay no attention to what the parts counterperson says. They’ll say the lower bushing can’t be had by itself.

The next area is under the hood. Disconnect the negative battery cable from the battery. Remove the slave cylinder and position it out of the way. There is one bolt near the 1 o’clock position on the bell housing (as viewed from the flywheel end of the engine) that attaches an engine lifting bracket. Don’t remove the bolt, as it is threaded through the engine and has a nut on its other side of the bell housing. Remove only its nut. This nut is easily reached from the top while you’re pulling the slave cylinder.

Next, put the car on a lift and remove the lower shielding from the catalytic converters. Depending on the year, there may be two or three converters. The ‘79s and ‘80s don’t have converters but a ridiculously complex front exhaust pipe and heat exchanger for emissions purposes. If your car has converters, remove them as an assembly. Remove the two nuts from the rear of the main (rear) converter and the two nuts from the front converter at the exhaust manifold. Leave the air injection tube attached to the converter, but remove it from the rubber hose attached at the check valve end of the tube. Remove the hangers from the converters and remove all three (or both) together, attached to one another with the air tube. If the car is pre ‘81, remove the exhaust hanger from the transmission, but otherwise leave the exhaust system intact.

Next, remove the heat shielding from the floor of the car that is held on by 10mm bolts and spacers. Then remove the driveshaft and plug the end to keep the oil from running out. A note on driveshafts. Mazda was very fond of changing driveshafts and differential pinion flanges over the years. What’s important to note is that universal joints are replaceable in years ‘79 through ‘82. From ‘83 and beyond, the joints are peened into the yokes and replacement of the joints is impossible. You’ll need to buy a complete driveshaft which, depending on the year, can run from $320 to $420. And because of the pinion flange changes (you guessed it), you can’t put the early shafts in the later cars!

Now disconnect the wiring and speedometer cable from the transmission. Remove the starter and support it. One starter bolt is short and attaches the bottom of the starter to the bell housing. The other starter bolt comes through the bell housing from the engine side and threads into the starter. Don’t let the starter hang, especially on carbureted cars. Those cars have a fusible link attached to the starter which is easily damaged if the starter is left hanging free by the battery cable.

Remove the remaining bell housing bolts. Remove the small cross member from the floor of the car and from the transmission mount. Remove the transmission with your favorite transmission jack.

Remove the pressure plate bolts one turn at a time until the spring pressure is released from the disc. Note that four of the pressure plate mounting bolts may have threads all the way up to their heads, while the remaining two bolts don’t. (Some years use dowels.) Those two bolts are alignment bolts that should go back into the two positions in the flywheel that also are missing threads at the top of the holes.

With the pressure plate and disc out of the way, it’s time to remove the pilot bearing. A pilot bearing puller is just about a must for this job. Occasionally you’ll find a pilot bearing with all of the needles missing (ground into oblivion).

The pilot bearing is small, and its shell thin. If the needles are all gone, you may have to carefully collapse the shell with a chisel to remove it. The pilot bearing also has a seal in front of it. Always replace the bearing and seal, as the pilot bearing is a high wear item.

In order to pull the flywheel, you’ll need a 2-1/8" socket and a puller such as that for a harmonic balancer. The large nut is the only thing holding the flywheel to the eccentric shaft (rotary speak for a crankshaft). The flywheel fits a taper on the shaft and has a keyway to locate it. The torque spec on this behemoth is 362 ft.lbs. A good half inch impact wrench should remove the nut. Leave the nut screwed on a few turns, then set up the puller in the threaded holes of the flywheel (near the pilot bearing area) for this purpose. Don’t allow the puller screw to go inside the pilot bearing. There is an aluminum plug in the end of the eccentric shaft that terminates an oil galley.

Damaging the plug could be a disaster. Apply some tension to the puller, then tap the end of the puller screw with a hammer to break the flywheel loose. Leaving the nut on prevents the flywheel from falling on your toes when it breaks loose.

The flywheels are fairly massive (up to 30 lbs., depending on the year). Because of this, they may not need grinding. If there are blue spots, cracking or ridging, it must be resurfaced. Otherwise, some light sanding of the friction surface should be sufficient. Since the flywheel does not mount to the engine conventionally, be sure your machine shop can resurface the flywheel. Be sure to maintain the correct offset of the stepped flywheel.

Take a look for oil leaks. The rear main seal lip seals on the flywheel itself. Rear main seals aren’t known for leaking, but if it’s suspect, spend the $15 and replace it. Remove the release bearing and fork from the transmission. Oil leaks are common on ‘86 to ‘88 non-turbo transmissions. The problem is that the front bearing retainer (cover) bolts loosen and the gasket leaks. If you find loose bolts and a leak, replace the gasket (PN# 8540-16-225) and reinstall the bolts with thread locking compound. Torque to 19 ft.lbs.

Install a new release bearing and lightly lubricate the release fork pivot ball and sliding area of the bearing with wheel bearing grease. Install the flywheel using thread locking compound on the nut. You can torque the nut if you wish. Another option is to use some thread locking compound and tighten the nut with an impact wrench. Install and lubricate the pilot bearing and seal.

Hold the disc up to the flywheel (be sure the correct side is facing the flywheel) and insert the alignment tool through the splines and into the pilot bearing. Now place the pressure plate squarely against the disc. Install all pressure plate bolts finger tight. Now tighten all of the bolts one turn at a time, in a crisscross pattern, to prevent warping or damaging the pressure plate. Torque the pressure plate bolts to 20 ft.lbs.

Transmission installation is basically the reverse of removal. Replace the two exhaust gaskets, if necessary. They are metal/asbestos gaskets and are often OK to reuse. Top off all transmissions with 75W90 GL4 or GL5 gear oil.

There are a few idiosyncrasies in the area of shifter installation. When you install the shifter down into the transmission, you’ll notice a spring that wraps around the main shift shaft and pushes on the side of the shifter lever. This spring centers the shifter, so that there is slight tension keeping the shifter in the third and fourth gear gate. Be sure to install the shifter so that the spring is pushing on the right side of the it, not the left.

When installing the shifter retainer plate and its three bolts, make sure the wave washer and flat washer are centered over the upper shifter bushing. If after assembly the shifter movement feels stiff, the washers are not concentric with the bushing. You have to eyeball this, there’s nothing to help with alignment.

You should not have had to disconnect any wiring in the vicinity of the shifter. Therefore, don’t connect any now. The point here being that there are some extra wires down there that are used for automatic transmission shifter indicator (PRNDL) illumination. One is the feed from the instrument panel rheostat, the other a ground. They will connect to each other, instantly frying the $85 rheostat when the lights are turned on. I’ve seen this more than once!

Following these tips and recommended practices should keep you from going round and round on a rotary clutch job!