The following is reprinted with permission from the author John de Armond.
All information published here is the property of the original authors who are members of The IZCC and may not be reproduced for commercial purposes.
Everything stated here is based on the experiences and opinions of the original authors. The authors and editor accept no responsibility for any damages arising from use of this information. Always consult your owner's manual and take appropriate precautions when working on your car. If in doubt consult a specialist.
Have you noticed that your 4 or 5 speed manual transmission shift lever is getting loose, that the action is sloppy, that maybe it twists a bit as you shift? Is that what's bothering you? Well, here's how to fix it in the privacy of your own home.
This problem is caused by the fact that the bushing on which the shift lever pivots is some kind of composition material that tends to wear out or disintegrate. In my case (75 280), the bushing was completely gone so I really don't have any idea what it was made of.
To get to this bushing, first remove the center console after unscrewing the shift knob. Underneath is a rubber boot that seals the shifter from the outside. Remove the 4 screws that hold it on and get it out of the way. You will see the snout of the transmission. There should be another small boot that seals the entrance of the shift lever into the transmission. Pull this boot upward and off. You will see a clevis-pin arrangement. The shift lever is held in place by a pin that inserts through a stamped clevis assembly and is held in place by a "C" ring. Remove this ring and the pin. The shift lever then just pulls up and out. There should be a cylindrical plastic bushing on the end of the shifter. It should be free to pivot but not sloppy.
Examine the hole where clevis pin came out. There should be a bushing of some sorts there. If there is only the shift rod, then the bushing has broken up and disappeared. If any residue is in the hole, punch it out with a punch and hammer.
We'll now make a new bushing out of brass. At this point, a lathe is handy but a drill press or electric drill and some files will do. The raw material of choice is porous, oil impregnated bronze but since we're doing this at home, brass will have to do. I started with a brass double ended 3/8" male pipe coupling.
The procedure is simple. Chuck one end of this coupling in your drill press or electric drill clamped in a vice. Select a medium grade file and, pushing it against the rotation of the drill, slowly square off the fitting and reduce it's diameter until it is about 0.010 larger than the hole in the shift rod. Then select a fine tooth file and take an additional 0.005 off so that you have about 0.005 interference fit. If you don't have calipers or a mike, this fit is about when the part will almost start into the hole in the shifter but needs considerable force to actually go. Machine the part all the way up to and including the wrench flats on the coupling. When you finish, you should have a piece with threads on one end, a shoulder, followed by a finely finished cylinder on the other.
The part is pressed into the shifter rod all the way up to the shoulder. If you don't have a press, a vice and a socket will do fine. Invert the socket so the bolt end is out, place the shifter rod on top of the socket and start the new bushing from the other side. Squeeze the whole assembly in the vice until it snugs into place.
Next, take a hack saw and cut the bushing off flush with the sides of the shift rod. Take a fine file and smooth the surfaces until the bushing is absolutely flat with the rod. Polish with emery cloth.
Next, the center hole must be bored to the correct diameter to accept the clevis pin. A 23/64" drill happens to be exactly the right size for this operation. You must work up to this size in several steps. If you try to go all at once, the soft brass will grab the bit and likely destroy the bushing if not the bit. Drill slowly and carefully, trying not to heat the part. I use 1,1,1 tricloroethane as a cutting fluid. Liquid dishwashing detergent also works well. Deburr the hole with a pocket knife and the job is done.
Reassemble the shifter mechanism and enjoy. You will find that the shifting action gains a precision you've probably never experienced in a Z before. It's absolutely great to be able to feel the gears engage on each shift. Plus there is no more buzzing in the lever at high RPM.
John de Armond