Clutch Replacement Tips

The following are a few random thoughts on changing clutches. These tips are more oriented to the rookie mechanic than the veteran clutch-changer, however there are always new things to learn about a process most of us do not enjoy. Things You Will Need To Buy

• New Pressure Plate. The pressure plate size is dictated by the flywheel; determine the correct replacement before purchasing. Nissan pressure plates are strongly recommended.
• Clutch Disc The clutch disc size is dictated by the pressure plate. Nissan clutch discs are recommended but other brand names are suitable.
• Throw-Out Bearing This part needs to be matched to the pressure plate, not the transmission. Typically you would purchase the pressure plate, clutch disc, and throw-out bearing as a kit.
• Pilot Bushing
• Clutch Alignment Tool (if you do not have one, or one was not included in your clutch kit)
• Exhaust Flange Gasket (exhaust manifold to exhaust pipe) Note that 1972 and later are different!
• Grease. Bearing grease is suitable.

The following things are easy to replace while changing out a clutch. It would be a lot of work to pull the transmission 10,000 miles down the road just to change out a newly-failed input shaft seal.

• Input Shaft Seal and Front Cover Gasket
• Output Shaft Seal
• Pressure Plate Dowel Pegs (3)
• Two Quarts of Transmission/Gear Fluid (90W)

If this is your first or second clutch change, it would be a very good idea to have a repair manual on hand; this article won't cover the entire clutch-replacement procedure. The best manual for the job is the "How to Keep your Datsun/Nissan Alive" repair book. The factory service manual is also worthwhile. You will also need the normal array of mechanic's tools, including but not limited to a friendly helper, a floor jack, jack stands, metric socket set, metric end-wrench set, and pry bars.

Note, not all clutch replacements are caused by normal wear. My '71 4 door has 65K miles on it, with a note the clutch was replaced at 35K miles, ten years ago! The clutch was out of adjustment, causing the disc to slip, overheating the pressure plate. The sad part is, had it been adjusted over time, the clutch probably would not have needed to replacement. Just another reason to follow the factory maintenance schedule.

The Nitty-Gritty

• Steam clean the car's underside the day before. If possible, get the car up on ramps and clean the bell housing, driveshaft, and driveline areas. The more time spent cleaning, the easier the job becomes.
• When you place your car up on jack stands, make sure your car is stable. You will be shaking the transmission above your head and body, you do not want the car to shift or slip off the jack stands. Good jack stands are reasonably inexpensive; spend the money and buy four good jack stands. Mine safely lift the car 18" high, which is just about right.
• A stock exhaust system will most likely be rusted tight, especially at the manifold-to-midpipe connection. Liberally coat the flange, bolts, and exposed threads with PB Blaster or similar penetrating oil. Give the oil a few minutes to work. Depending on the exhaust system you might not need to fully remove anything. With stock exhaust (or properly designed custom systems) you can simply loosen the three flange nuts so that the engine will tilt. The driveline should be removable past the exhaust pipe unless someone has designed the pipe to tuck up into the tunnel. If the system is still original (or has been in there for many years) the chance of breaking one or more of the three manifold studs is huge. If you can’t get the nuts to release fairly easily it’s better to cut the pipe on some straight section and later buy a “connector” and a couple clamps at your local parts store and put it back together that way. Replacing broken rusty studs isn’t something you want to deal with while swapping a clutch. Better to save that for another project.
• To spare me some grief, whenever I have an exhaust replaced I have an exhaust flange added about halfway down, just past the transmission. This makes the removal of the exhaust pipe much easier, and transmission mission jobs go quicker.
• You'll need to keep the driveshaft from turning while removing the driveshaft bolts - pull the parking brake. When you have the driveshaft bolts loose, release the parking brake, then remove the little clip about half way along the floor and move the cable out of the way.
• Use the front splined portion of an old driveshaft (see photo 3) as a plug to avoid having to drain the oil. You can NEVER get enough oil out to avoid it spilling out the tailhousing.
• Place a section of 4x4 wood post on top of the floor jack, then jack the wood up under the front lip of the oil pan to tilt the engine back and to support the engine once the transmission has been removed. A scissor jack on the 4x4 piece of wood, with a 1/2" thick piece of wood between it and the oil pan, will also work well.
• Support the transmission with a floor jack, then remove the transmission cross member. I've learned it is easier to get those two top bolts after removing the crossmember and tilting the transmission down.
• When tilting the transmission down, watch the fan radiator fan. I put the fan blades in an "X" position; this will give a little more clearance. Also keep an eye on the radiator hoses – some installations have more give than others. (Note: L20B has much less “stretch” in the upper radiator hose.) You want to remove the carburetor linkage that connects carb to firewall. That part can actually come up against the firewall when you get the engine tilted and bend stuff. With the correct angle, the front of the engine tilted up, remove all bolts securing the transmission to the engine and remove the clutch slave cylinder. With the transmission unbolted, simply roll the floor jack back. Piece of cake (wish is was always this way).
• Old clutch discs containing asbestos fibers should be considered hazardous waste. Do not toss it into the trash can.
• Leave the flywheel dowel pegs in the flywheel when taking the flywheel in to get surfaced. The machine shop will have the experience and correct tools to remove and replace these parts, if necessary. The dowel pegs need to securely locate the pressure plate while threading in and tightening the pressure plate bolts. Mangled dowel pegs can result in a pressure plate being tightened off center.
• To replace the pilot bearing, you can use the grease trick. Pack the input shaft hole in the crankshaft full of wheel bearing grease (it helps to toss the grease into the freezer a day before to keep it thick). Use a 1/2" rod to pack it in, letting the air out as you fill the hole with grease. A 5/8" hardwood dowel soaked in oil to swell it is the ideal tool for this trick; insert the down in the back of the crankshaft and hit the dowel with a dead-blow hammer. The grease will not compress, but the force of the hammer blows will push on the grease, pushing the old pilot bushing out of the crank.
• If you have a relatively stock engine, you may not need to replace the flywheel bolts. Consult your manual. However, if you have a high-performance engine, or one that is turbocharged, it is recommended you replace these bolts whenever you remove the flywheel.
• To torque the flywheel bolts, I hold the flywheel in place using a couple of bolts threaded into the pressure plate holes. Place a pry bar between these bolts while you tighten the flywheel bolts. Do not use the bolts you will use to secure the pressure plate to the flywheel. I have a couple of socket cap bolts that I use for this, and for removing stuck drums - 8mm x 1.25 threading, 25mm long.
• The pressure plate bolts are only torqued to 18 ft-lbs, so SNUG will do it. You may want to replace these bolts if you were not the person to torque them last time. You have to tighten these bolts in a star pattern, just a little at a time as you are clamping down the pressure plate when tightening it. Always look back at the pressure plate once those bolts are snug. Are all the pressure plate fingers even and at the same angle? I’m a big believer in using Loctite on flywheel and clutch cover bolts. If you REALLY rev your L-series the clutch bolts in particular loosen over time. I have found loose flywheel bolts that I know I tightened to proper spec. A litte Blue Locktite goes a long way to making me more comfortable.
• Use a wire brush, and clean all the crud out of the transmission-to-engine bolt threads. Makes getting everything back together much quicker when you can thread the bolts with your fingers.
• Lightly grease the transmission input shaft splines, the throw-out bearing sleeve, and the pivot points of the throw-out bearing arm. The transmission bellhousing looked dry inside, but there was a fair coating of black dust. This is ASBESTOS, do not blow it out, just clean it up with a rag and a can of brake cleaner.
• Replace the front transmission gasket and seal at this step, if you have the parts and feel the need.
• I line up the splines on the input shaft by placing the transmission in gear and twisti the driveshaft to line them up. It’s the ONLY way to go and can literally save an hour trying to get the splines aligned. And make sure you DO NOT let the transmission input shaft “hang” in the clutch disk hole…ever. You can actually bend the disk assembly.
• After reassembling the transmission to the engine and reinstalling the clutch slave cylinder, step on the clutch pedal to confirm it feels good before reinstalling the rest of the parts.
• While I had the starter off I slipped off the back cover (two 10mm hex-head bolts, and two screws) to inspect the brushes. I just like doing those little inspections while I have the item off the car.