technogon

Since it is bad even when stopped, I suspect the clutch not disengaging. Could be the master or slave cylinder or adjustment of the slave rod. Another option I found while searching around was a post about 5 speeds. I seems that 81 and earlier had a nut that would loosen in the trans causing the gears to move apart. This reduces the effectiveness of the syncros. See this address for details: http://www.zcar.com/forums/read.php?f=1&i=275513&t=275496 But first I would check out the clutch throw. You could increase the slave cyl rod length and see if it improves. It should not however cause slipping. That is going too far. See other posts and manual for details.

I have a 72 witha 5 speed. Shifting is not hard at all. Possibly the syncro rings are worn out or the clutch is not disengaging enough. Is it hard to get into 1st at a stop? If yes, the I suspect a clutch problem. If no, then I suspect syncro's. The job of the syncro is to match input and output shaft speeds by acting as a "brake" between them. When worn, you have to push hard to get the braking and matching action. As they wear they loosen and loose effectiveness. When gone, gears grind instead.

Just replaced clutch in 72 Z. Still slipping. Readjusted master cyl rod and slave rod. Has small amount of freeplay when released. So linkage is OK. Old clutch was smoked due to improper master cyl rod adjustment not allowing fluid return. Slips most in 5th (5 spd added long ago). Holds in 1st and 2nd. Common problem? Do I need a better pressure plate? Recommend? Motor is stock 72.